Journal articles: 'Buffer layers'

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Aytug, T., B. W. Kang, C. Cantoni, E. D. Specht, M. Paranthaman, A. Goyal, D. K. Christen, et al. "Growth and characterization of conductive SrRuO3 and LaNiO3 multilayers on textured Ni tapes for high-Jc Yba2Cu3O7–delta; coated conductors." Journal of Materials Research 16, no. 9 (September 2001): 2661–69. http://dx.doi.org/10.1557/jmr.2001.0365.

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Power applications of high-temperature superconducting (HTS) coated conductors will require stabilization against thermal runaway. We have developed conductive buffer layers to electrically couple the HTS layer to the underlying metal substrate. The structure comprises the layer sequence of SrRuO3 (SRO) on LaNiO3 (LNO) on biaxially textured Ni substrates. We report baseline investigations of compatibility of SRO/LNO multilayer structure with processing of Yba2Cu3O7−δ (YBCO) and demonstrate biaxially textured YBCO films on conductively buffered Ni tapes. These YBCO coatings exhibit self-field Jc values as high as 1.3 × 106 A/cm2 at 77 K, and the entire structure (HTS + conductive buffers + metal substrate) shows good electrical connectivity. These results demonstrate that SRO/LNO buffer layers may provide a basis for stabilized coated conductors.

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Núñez-Cascajero, Arántzazu, Fernando B. Naranjo, María de la Mata, and Sergio I. Molina. "Structural Characterization of Al0.37In0.63N/AlN/p-Si (111) Heterojunctions Grown by RF Sputtering for Solar Cell Applications." Materials 14, no. 9 (April 27, 2021): 2236. http://dx.doi.org/10.3390/ma14092236.

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Compact Al0.37In0.63N layers were grown by radiofrequency sputtering on bare and 15 nm-thick AlN-buffered Si (111) substrates. The crystalline quality of the AlInN layers was studied by high-resolution X-ray diffraction measurements and transmission electron microscopy. Both techniques show an improvement of the structural properties when the AlInN layer is grown on a 15 nm-thick AlN buffer. The layer grown on bare silicon exhibits a thin amorphous interfacial layer between the substrate and the AlInN, which is not present in the layer grown on the AlN buffer layer. A reduction of the density of defects is also observed in the layer grown on the AlN buffer.

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Kharchenko, V. A. "HETEROSTRUCTURE BUFFER LAYERS." Izvestiya Vysshikh Uchebnykh Zavedenii. Materialy Elektronnoi Tekhniki = Materials of Electronics Engineering 19, no. 3 (March 5, 2018): 189–94. http://dx.doi.org/10.17073/1609-3577-2016-3-189-194.

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Dunstan, D. J. "Relaxed buffer layers." Semiconductor Science and Technology 6, no. 9A (September 1, 1991): A76—A79. http://dx.doi.org/10.1088/0268-1242/6/9a/013.

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Piquette, E. C., P. M. Bridger, R. A. Beach, and T. C. McGill. "Effect of Buffer Layer and III/V Ratio on the Surface Morphology of Gan Grown by MBE." MRS Internet Journal of Nitride Semiconductor Research 4, S1 (1999): 417–22. http://dx.doi.org/10.1557/s1092578300002829.

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The surface morphology of GaN is observed by atomic force microscopy for growth on GaN and AlN buffer layers and as a function of III/V flux ratio. Films are grown on sapphire substrates by molecular beam epitaxy using a radio frequency nitrogen plasma source. Growth using GaN buffer layers leads to N-polar films, with surfaces strongly dependent on the flux conditions used. Flat surfaces can be obtained by growing as Ga-rich as possible, although Ga droplets tend to form. Ga-polar films can be grown on AlN buffer layers, with the surface morphology determined by the conditions of buffer layer deposition as well as the III/V ratio for growth of the GaN layer. Near-stoichiometric buffer layer growth conditions appear to support the flattest surfaces in this case. Three defect types are typically observed in GaN films on AlN buffers, including large and small pits and “loop” defects. It is possible to produce surfaces free from large pit defects by growing thicker films under more Ga-rich conditions. In such cases the surface roughness can be reduced to less than 1 nm RMS.

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Kujofsa, Tedi, and John E. Ayers. "Threading Dislocations in S-Graded ZnSxSe1-x/GaAs (001) Metamorphic Buffer Layers." International Journal of High Speed Electronics and Systems 23, no. 01n02 (March 2014): 1420005. http://dx.doi.org/10.1142/s0129156414200055.

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Metamorphic semiconductor devices are commonly fabricated with linearly-graded buffer layers, but equilibrium modeling studies suggest that S-graded buffers, following a normal cumulative distribution function, may enable lower threading defect densities. The present work involves a study of threading dislocation density behavior in S-graded ZnS x Se 1-x buffer layers for metamorphic devices on mismatched GaAs (001) substrates using a kinetic model for lattice relaxation and misfit-threading dislocation interactions. The results indicate that optimization of an S-graded buffer layer to minimize the surface threading dislocation density requires adjustment of the standard deviation parameter and cannot be achieved by varying the buffer thickness alone. Furthermore, it is possible to tailor the design of the S-graded buffer layer in such a way that the density of mobile threading dislocations at the surface vanishes. Nonetheless, the threading dislocation behavior in these heterostructures is quite complex, and a full understanding of their behavior will require further experimental and modeling studies.

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Li, Guo, Minghua Pu, Huaming Zhou, Xiaohua Du, Yanbing Zhang, and Yong Zhao. "Possible new single-buffer layers for YBa2Cu3O7−y coated conductors prepared by chemical solution deposition." Journal of Materials Research 22, no. 9 (September 2007): 2398–403. http://dx.doi.org/10.1557/jmr.2007.0320.

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New single-buffer layers of YBiO3 and SmBiO3 have been proposed for YBa2Cu3O7−y (YBCO) and SmBa2Cu3O7−y coated conductors. Highly c-axis oriented YBiO3 and SmBiO3 buffer layers have been deposited on single-crystal LaAlO3 and SrTiO3, respectively, by a low-cost chemical solution deposition method in a temperature range as low as 730 to 800 °C in air. Precursor solution of yttrium nitrate, samarium nitrate, and bismuth nitrate has been deposited using spin coating and heat treated in air in a single stage to yield textured YBiO3 and SmBiO3 buffers. A very dense, smooth, pinhole-free, and crack-free morphology has been observed for both buffers. Dense, homogeneous, and epitaxially grown YBCO film with thickness about 300 nm has been obtained on YBiO3 buffer with onset critical temperature 90 K and Jc (77 K, self-field) over 3 MA/cm2. These results offer an effective alternative to prepare desirable buffer layer(s) for YBCO-coated conductors.

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Wu, Xiao Chen, Xiao Xia Zhong, Wei Zhou, Lu Qi Yuan, Qi Wei Shu, and Yu Xing Xia. "Hydroxyapatite Films Deposited on TiN and TiO₂ Buffer Layers by Radio-Frequency Magnetron Sputtering: Comparative Study." Key Engineering Materials 334-335 (March 2007): 1133–36. http://dx.doi.org/10.4028/www.scientific.net/kem.334-335.1133.

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A comparative study was presented to demonstrate the clear influence of the different buffer layer (TiN and TiO2) on the HA film. In this study, magnetron sputtering was applied for different film deposition. Nano-indentation was used to examine the mechanical properties of the HA film on both TiN and TiO2 buffer layers. It is found that HA film on TiN buffer layer is harder and the HA film on TiO2 buffers is more rigid. Further more, the simulated body fluid (SBF) soaking test was selected to investigate the properties of the HA/TiN and HA/TiO2 films in the physiological media. The obvious delamination was observed on the surface of HA film on TiN buffer layer, while the surface morphology of HA film on TiO2 buffer layer remained nearly unchanged. The result indicated that TiO2 buffer layer shows a better interfacial bonding to the HA film.

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Wang, Xiao Jing. "Effects of Al₂O₃ Buffer Layer on the Properties of ZnO: Al Thin Films Deposited on Glass by Sputtering." Materials Science Forum 848 (March 2016): 301–4. http://dx.doi.org/10.4028/www.scientific.net/msf.848.301.

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The ZnO:Al (AZO) films were deposited on glass substrates with Al2O3 buffer layers by RF magnetron sputtering. The obtained films had the hexagonal structure and preferred orientation of (002). Compared with AZO film without buffer layer, the grain size of the film with buffer layer was increased and the conductive property was increased greatly. the grain size of AZO films reached 27.9nm for those with buffer layers. The optical property of AZO films was decreased by the buffer layers. The resistivity of AZO films with Al2O3 buffer layer was about 6.6×10-3 Ω·cm and the average transmittance was over 80% in the range of 450~900nm.

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Oh, Yong Jun, Jung Seok Ra, and Ui Gil Lee. "Effects of Deposition Parameters on the Crystallinities of CeO₂ and Y₂O₃ Buffer Layers on Textured Ni Deposited by Magnetron Sputtering." Solid State Phenomena 124-126 (June 2007): 779–82. http://dx.doi.org/10.4028/www.scientific.net/ssp.124-126.779.

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The epitaxial growth conditions of CeO2 and Y2O3 single buffer layers on textured Ni tapes were examined using rf magnetron sputtering, and the process conditions for the sequential and mixture buffer layers of these two materials were investigated respectively in order to develop a more simplified buffer architecture. The CeO2 single layer exhibited a well developed (200) epitaxial growth at Ar/10%O2 gas below 450°C, although the epitaxial property was decreased with increasing layer thickness. With regard to the deposition of Y2O3 on Ni, the epitaxial growth was not successful. The epitaxy of Y2O3 on Ni was very sensitive to the O2 gas pressure during sputtering. The repeated sequential architecture of the CeO2 and Y2O3 layers exhibited a good epitaxial property at 400°C/(Ar/10%O2) for the initial CeO2 layer and 700°C/Ar and 700°C/(Ar/10%O2) for the subsequent Y2O3 and CeO2 layers, respectively. The Y-doped CeO2 buffers with (200) epitaxy were successfully obtained by the co-sputtering of Ce and Y metals in a reactive gas condition, and the maximum target Y/Ce ratio for the epitaxy was about 1/10.

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Mabuchi, Yuichiro, Tatsuya Masuda, Daisuke Muto, Kenji Momose, and Hiroshi Osawa. "Investigation of Carrot Reduction Effect on 4H-Silicon Carbide Epitaxial Wafers with Optimized Buffer Layer." Materials Science Forum 897 (May 2017): 75–78. http://dx.doi.org/10.4028/www.scientific.net/msf.897.75.

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We investigated the carrot-defect reduction effect by optimizing the buffer layers of 4H-Silion Carbide (SiC) epitaxial wafers. The SiC epitaxial wafer with the 0.5 μm-thick optimized condition-B buffer layer show the carrot-defect density of 0.13 cm-2, since that with the conventional-A buffer layer were 0.68 cm-2. Although the average bunching length with the optimized condition-B buffer layer was 7-times longer than those with the conventional condition-A buffer layer, we could reduce the bunching length by applying the optimized condition-B only to the initial 0.05 μm-thick buffer layer. Finally, with the initial 0.05 μm-thick optimized condition-B buffer layers, we could achieve the SiC epitaxial wafers with only half the carrot-defect densities of those with the conventional condition-A buffer layers, while the average bunching lengths were less than 100 μm. With this condition, we could achieve the estimated yield of 90.1% with 4 x 4 mm chips, while that with the conventional condition-A buffer layer was 81.9%.

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Tawara, Takeshi, Tetsuya Miyazawa, Mina Ryo, Masaki Miyazato, Takumi Fujimoto, Kensuke Takenaka, Shinichiro Matsunaga, et al. "Suppression of the Forward Degradation in 4H-SiC PiN Diodes by Employing a Recombination-Enhanced Buffer Layer." Materials Science Forum 897 (May 2017): 419–22. http://dx.doi.org/10.4028/www.scientific.net/msf.897.419.

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Application of highly N-doped buffer layers or a (N+B)-doped buffer layer to PiN diodes to suppress the expansion of Shockley stacking faults (SSFs) from the epilayer/substrate interface was studied. These buffer layers showed very short minority carrier lifetimes of 30–200 ns at 250°C. The PiN diodes were fabricated with buffer layers of various thicknesses and were then tested under high current injection conditions of 600A/cm2. The thicker buffer layers with shorter minority carrier lifetimes demonstrated the suppression of SSFs expansion and thus that of diode degradation.

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Chibirova, F. Kh, G. V. Kotina, E. A. Bovina, D. V. Tarasova, A. A. Polisan, and Yu N. Parkhomenko. "Effect of magnetic structural processing on structure and texture of La2Zr2O7 buffer layers." Modern Physics Letters B 30, no. 32n33 (November 30, 2016): 1650390. http://dx.doi.org/10.1142/s0217984916503905.

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Epitaxial CeO2 seed layer and La2Zr2O7 (LZO) buffer layers were deposited on biaxially-textured Ni–5 at.% W (NiW) tape substrate by liquid-phase polymer assisted nanoparticles deposition (PAND) method. LZO layers deposited by PAND have consistently shown tilting of the [Formula: see text]-axis toward the direction of the sample’s surface normal. A new approach increasing the sharpening of the buffer texture by magnetic structural processing (MSP) of buffer layers was tested. The LZO layers, deposited on the seed and buffer layers after MSP, have dense and smooth surface structure, and more importantly, significantly improved out-of-plane texture, compared with the LZO layers that were deposited on a layer without MSP. Transmission electron microscopy study confirmed the [Formula: see text]-axis tilting of CeO2 and LZO layers and revealed the absence of interfaces between LZO layers which have been grown on the layers after MSP. There are very small (2–4 nm) gated pores in the single-crystal structure of LZO layers that are not typical for structure of LZO layers obtained by liquid-phase methods. Thus the LZO buffer layers can serve as an effective metal-ion diffusion barrier.

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Zhao, Qi, Ming Jiang Dai, Di Tan, Chun Bei Wei, Wan Qi Qiu, and Hui Jun Hou. "Fabrication of Diamond Films on Cu Metal Substrates with Buffers (SiC or MoSi₂) by Hot Filament Chemical Vapor Deposition." Advanced Materials Research 936 (June 2014): 276–81. http://dx.doi.org/10.4028/www.scientific.net/amr.936.276.

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Diamond films were grown by hot filament chemical deposition (HFCVD) on Cu metal substrate with two different buffer layers (SiC or MoSi2) synthesized by using magnetron sputtering technique. The components of films were investigated using X-ray diffraction (XRD) and laser Raman spectrum, and the surface morphology and structure were observed with scanning electron microscopy (SEM). Film adherence was investigated by micro-indentation. The results showed that the diamond films were successfully grown on Cu metal substrate with two different buffer layers. There were cracks on diamond film grown on 3µm SiC buffer layer and some SiC crystal whiskers were observed. Dense diamond films with bad adhesion were observed on 22µm MoSi2 buffered copper substrate. MoSi2 made chemical reaction with CH4 and produced MoC and Mo5Si3 on the process of HFCVD. Conclusion: the 3µm buffer layer of SiC can’t help deposit no cracking diamond film; the 22µm buffer layer of MoSi2 is helpful for depositing good diamond film, but can’t effectively improve the bond strength between diamond film and copper substrate.

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Kharchenko, Vyacheslav A. "Buffer layers in heterostructures." Modern Electronic Materials 3, no. 4 (December 2017): 154–57. http://dx.doi.org/10.1016/j.moem.2017.11.006.

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Schowalter, Leo J. "Substrate Engineering With Plastic Buffer Layers." MRS Bulletin 21, no. 4 (April 1996): 45–49. http://dx.doi.org/10.1557/s0883769400035338.

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The advantage that epitaxy offers the electronics and optoelectronics industries is that it allows the possibility of producing precisely controlled layers of very high crystal quality. Heteroepitaxy of different materials offers the promise of tailoring device layers in clever ways that nature did not intend. However unlike fruit juices, nature has made it difficult to epitaxially combine different materials. As the preceding articles have clearly pointed out, it is very difficult to obtain smooth epitaxial layers that are free both of defects and strain when there is a lattice mismatch between the layers and their substrates.As already discussed in this issue, a uniform network of dislocations at the interface between a flat, uniform epitaxial layer and its substrate can completely relieve strain in the majority of the epitaxial layer. This would be a satisfactory situation for many devices so long as the active region of the device could be kept away from the interface. The problem is how to introduce the dislocations in an appropriate way. When an epitaxial layer has a larger lattice parameter than the underlying substrate, a misfit dislocation running along the interface represents a plane of atoms that has been removed from the epitaxial layer. (One would insert a plane of atoms if the epitaxial lattice parameter was smaller. For simplicity however we will continue to assume that the epitaxial layer has a larger lattice parameter.) It is not possible for a whole half plane of atoms, bounded by the dislocation at the interface and the substrate edges along the two sides, to be removed at once. The boundary between where the extra plane of atoms has been removed and where the epitaxial layer has not relaxed yet will represent a threading dislocation. This threading dislocation would continue to move as the size of the misfit dislocation along the interface grows. Ideally it moves all the way out to the substrate edge and vanishes there while the misfit dislocation along the interface would end up extending from one side of the substrate to the other. However other dislocations and other kinds of defects can effectively pin the threading dislocation resulting in an epitaxial layer with many threading dislocations. Unfortunately these threading dislocations are generally detrimental to most kinds of devices. It is precisely this high density of threading dislocations that limits applications of many heteroepitaxial layers.

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Islam, Md Tanvirul, Xinkang Chen, Tedi Kujofsa, and John E. Ayers. "Chirped Superlattices as Adjustable Strain Platforms for Metamorphic Semiconductor Devices." International Journal of High Speed Electronics and Systems 27, no. 01n02 (March 2018): 1840009. http://dx.doi.org/10.1142/s0129156418400098.

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Chirped superlattices are of interest as buffer layers in metamorphic semiconductor device structures, because they can combine the mismatch accommodating properties of compositionally-graded layers with the dislocation filtering properties of superlattices. Important practical aspects of the chirped superlattice as a buffer layer are the surface strain and surface in-plane lattice constant. In this work two basic types of InGaAs/GaAs chirped superlattice buffers have been studied. In design I (composition modulated), the average composition is varied by modulating the composition of one of the two layers in the superlattice period, but the individual layer thicknesses were fixed. In design II (thickness modulated), the individual layer thicknesses were modulated, but the compositions were fixed. In this paper the surface strain and surface in-plane lattice constant for these chirped superlattices are presented as functions of the top composition and period for each of these basic designs.

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KALAYCI, Taner. "Investigation of Cap and Buffer Layer Effect in Co/Ni Thin Films by Ferromagnetic Resonance Technique." Karadeniz Fen Bilimleri Dergisi 13, no. 2 (June 15, 2023): 724–33. http://dx.doi.org/10.31466/kfbd.1282051.

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In this study, the magnetic properties of Si(100)/X5/(Co0.3/Ni0.5)3/Y5 (X: Pt, Cu and Y: Pt, Cu, all thicknesses are nm) multilayers were investigated using ferromagnetic resonance technique (FMR). In sample sets all layers (buffer, cap, and Co) were grown by magnetron sputtering while Ni sub-layers were grown by molecular beam epitaxy (MBE) at high vacuum. The effective magnetic anisotropy is 300 mT when copper is used as the buffer and cap layer, 290 mT when the buffer layer is copper, and the cap layer is Pt. On the other hand, it is seen that the effective magnetic anisotropy is 350 mT when Pt is used as buffer and cap layer, and 150 mT when Pt buffer and Cu cap layer are used. Furthermore, magnetic easy axis is out of plane when the Pt buffer layer is used, while the magnetic easy axis is parallel to the plane when the Cu buffer layer is used. The results show that the buffer and cap layers of Co/Ni thin films, which are frequently used in the field of spintronics influence the magnetic properties.

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19

Ross, Jennifer, Mike Rubin, and T. K. Gustafson. "Single crystal wurtzite GaN on (111) GaAs with AlN buffer layers grown by reactive magnetron sputter deposition." Journal of Materials Research 8, no. 10 (October 1993): 2613–16. http://dx.doi.org/10.1557/jmr.1993.2613.

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We report the growth conditions necessary for highly oriented wurtzite GaN films on (111) GaAs, and single crystal GaN films on (111) GaAs using AlN buffer layers. The GaN films and AlN buffers are grown using rf reactive magnetron sputter deposition. Oriented basal plane wurtzite GaN is obtained on (111) GaAs at temperatures between 550 and 620 °C. However, using a high temperature 200 Å AlN buffer layer epitaxial GaN is produced. Crystal structure and quality are measured using x-ray diffraction (XRD), reflection electron diffraction (RED), and a scanning electron microscope (SEM). This is the first report of single crystal wurtzite GaN on (111) GaAs using AlN buffer layers by any growth technique. Simple AlN/GaN heterostructures grown by rf reactive sputter deposition on (111) GaAs are also demonstrated.

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Mamta, Kamlesh Kumar Maurya, and Vidya Nand Singh. "Enhancing the Performance of an Sb2Se3-Based Solar Cell by Dual Buffer Layer." Sustainability 13, no. 21 (November 8, 2021): 12320. http://dx.doi.org/10.3390/su132112320.

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In an Sb2Se3-based solar cell, the buffer layer is sandwiched between the absorber and the window layer, playing an essential role in interfacial electricity. Generally, CdS is used as a buffer layer, but its toxic nature and low bandgap can cause current loss because of parasitic absorption. In this work, we optimized the buffer layer by using ZnS as an alternative to the CdS buffer layer in order to decrease the use of CdS. The effect of different buffer layers on the solar device was explored by numerical simulation with the help of SCAPS 1D software. The basic parameters, such as open-circuit voltage (Voc), current density (Jsc), fill factor (FF), and efficiency (η) were analyzed and compared for both the buffer layers (CdS/ZnS). The results demonstrate that changing buffer materials and thicknesses has a significant impact on cell performance. The efficiency for the ZnS buffer layer was lower compared to that of the CdS-based solar cells because of insufficient energy band alignment. In order to enhance the efficiency of Sb2Se3-based solar cells, we used CdS/ZnS dual buffer layers and studied the device performance. The work function of the back contact also affects the device performance, and for work functions below 4.8 eV, the device’s efficiency was very low. The effect of varying the thicknesses and temperatures of the buffer layers on the I-V/C-V characteristics, quantum efficiency, and energy band structure are also reported. This study shall guide the researcher in reducing CdS and improving the device’s performance.

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Kim, Ki Hwan, Liudmila L. Larina, Kyung Hoon Yoon, Makoto Konagai, and Byung Tae Ahn. "Growth of an In_x(OOH,S)_y Buffer Layer and Its Application to Cu(In,Ga)(Se,S)₂ Solar Cells." Materials Science Forum 475-479 (January 2005): 1681–84. http://dx.doi.org/10.4028/www.scientific.net/msf.475-479.1681.

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As an alternative to a CdS buffer layer for Cu(In,Ga)Se2-based solar cells, we prepared In-based buffer layers using a chemical bath deposition method. XPS and XRD analyses revealed that the In-based buffer layers contained In2S3 and InOOH phases. Compared with CdS film, the In-based film, Inx(OOH,S)y, had higher optical transmittance and a shorter absorption edge. The Cu(In,Ga)(Se,S)2 solar cell with the Inx(OOH,S)y buffer layer had better photovoltaic properties than that with a conventional CdS buffer layer. The conversion efficiency of the best Cu(In,Ga)(Se,S)2 solar cell with Inx(OOH,S)y buffer layer was 12.55 % for an active area of 0.19 cm2.

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Benamara, M., Z. Liliental-Weber, J. H. Mazur, W. Swider, J. Washburn, M. Iwaya, I. Akasaki, and H. Amano. "The Role of the Multi Buffer Layer Technique on the Structural Quality of GaN." MRS Internet Journal of Nitride Semiconductor Research 5, S1 (2000): 398–404. http://dx.doi.org/10.1557/s1092578300004567.

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Successive growth of thick GaN layers separated by either LT-GaN or LT-AlN interlayers have been investigated by transmission electron microscopy techniques. One of the objectives of this growth method was to improve the quality of GaN layers by reducing the dislocation density at the intermediate buffer layers that act as barriers to dislocation propagation. While the use of LT-AlN results in the multiplication of dislocations in the subsequent GaN layers, the LT-GaN reduces dislocation density. Based upon Burgers vector analysis, the efficiency of the buffer layers for the propagation of the different type of dislocations is presented. LT-AlN layer favor the generation of edge dislocations, leading to a highly defective GaN layer. On the other hand, the use of LT-GaN as intermediate buffer layers appears as a promising method to obtain high quality GaN layer.

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JIN, SEONG-EON, DOHAN LEE, SEUNGMOO LEE, JONG-MUN CHOI, BUMJOON KIM, CHANG GYOUN KIM, TACK-MO CHUNG, and DONG-JIN BYUN. "PROPERTIES OF COPPER LAYER ON Si(100) FROM Cu(dmamb)2." Surface Review and Letters 17, no. 03 (June 2010): 307–10. http://dx.doi.org/10.1142/s0218625x10013801.

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Cu seed layer was deposited by chemical vapor deposition using new Cu precursor, Cu(dmamb) 2. The Cu layers still need the barrier layer to prevent the diffusion, so Ta and Ti were used for the barrier layer on Si(100) . Low temperature (LT) copper buffer layer was introduced and the effect of the buffer on the Cu films was investigated. The grown Cu layers were analyzed using FESEM, XRD, and four point probe measurement. The Cu seed layers were successfully deposited using Cu(dmamb) 2 precursor. Better thickness uniformity was obtained in the Cu films with the LT Cu buffer, which lowered the electrical resistivity.

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Кобяков, А. В., И. А. Турпанов, Г. С. Патрин, Р. Ю. Руденко, В. И. Юшков, and Н. Н. Косырев. "Структурные и магнитные свойства систем Al-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=-/Ge-p/Al-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=-/Co." Журнал технической физики 89, no. 2 (2019): 268. http://dx.doi.org/10.21883/jtf.2019.02.47082.198-18.

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AbstractThe Al_2O_3/Ge- p /Al_2O_3/Co system with an Al_2O_3 buffer layer deposited by ion-plasma sputtering has been experimentally investigated. The dependences of the magnetic properties of cobalt on the rate of its deposition by ion-plasma sputtering and rate of deposition of preceding layers have been established. It is shown that the technique used to obtain buffer layers can significantly reduce the surface roughness of the next layers. The obtained buffer layers can be used as artificial substrates for growing heterostructures with tunnel junctions.

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Asaduzzaman, Md, Md Billal Hosen, Md Karamot Ali, and Ali Newaz Bahar. "Non-Toxic Buffer Layers in Flexible Cu(In,Ga)Se2Photovoltaic Cell Applications with Optimized Absorber Thickness." International Journal of Photoenergy 2017 (2017): 1–8. http://dx.doi.org/10.1155/2017/4561208.

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Absorber layer thickness gradient in Cu(In1−xGax)Se2(CIGS) based solar cells and several substitutes for typical cadmium sulfide (CdS) buffer layers, such as ZnS, ZnO, ZnS(O,OH), Zn1−xSnxOy(ZTO), ZnSe, and In2S3, have been analyzed by a device emulation program and tool (ADEPT 2.1) to determine optimum efficiency. As a reference type, the CIGS cell with CdS buffer provides a theoretical efficiency of 23.23% when the optimum absorber layer thickness was determined as 1.6 μm. It is also observed that this highly efficient CIGS cell would have an absorber layer thickness between 1 μm and 2 μm whereas the optimum buffer layer thickness would be within the range of 0.04–0.06 μm. Among all the cells with various buffer layers, the best energy conversion efficiency of 24.62% has been achieved for the ZnO buffer layer based cell. The simulation results with ZnS and ZnO based buffer layer materials instead of using CdS indicate that the cell performance would be better than that of the CdS buffer layer based cell. Although the cells with ZnS(O,OH), ZTO, ZnSe, and In2S3buffer layers provide slightly lower efficiencies than that of the CdS buffer based cell, the use of these materials would not be deleterious for the environment because of their non-carcinogenic and non-toxic nature.

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Rachedi, Merwan, Abdelkrim Merad, Giulio Lorenzini, Hijaz Ahmad, Younes Menni, Houari Ameur, and Ibtissem Sifi. "Effect of the Properties of Chalcopyrite Semiconductors on the Physical and Optical Parameters of Cell Layers with CIGS." Revue des composites et des matériaux avancés 31, no. 2 (April 30, 2021): 65–72. http://dx.doi.org/10.18280/rcma.310201.

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In this paper, the impact of various buffers of applying components on the effectiveness of CuInGaSe2 solar cells is studied numerically. The SCAPS software is employed to achieve the investigation. The main parameters of the inspected devices are: the photovoltaic conversion effectiveness (η), the filling factor (FF), short-circuit current (Jsc), and open circuit voltage (Voc). These photovoltaic parameters are analyzed vs. the thickness in the various buffer layers under study. The numerical findings revealed that the most significant conversion effectiveness (23.4%) of the CIGS solar cell is obtained with the CdS buffer layer. An attempt is conducted to improve this efficiency by using the SCAPS and by optimizing the two electrical and technological parameters of the three layers (ZnO, CdS, CIGS).

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Austin, Aaron J., Elena Echeverria, Phadindra Wagle, Punya Mainali, Derek Meyers, Ashish Kumar Gupta, Ritesh Sachan, S. Prassana, and David N. McIlroy. "High-Temperature Atomic Layer Deposition of GaN on 1D Nanostructures." Nanomaterials 10, no. 12 (December 5, 2020): 2434. http://dx.doi.org/10.3390/nano10122434.

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Silica nanosprings (NS) were coated with gallium nitride (GaN) by high-temperature atomic layer deposition. The deposition temperature was 800 °C using trimethylgallium (TMG) as the Ga source and ammonia (NH3) as the reactive nitrogen source. The growth of GaN on silica nanosprings was compared with deposition of GaN thin films to elucidate the growth properties. The effects of buffer layers of aluminum nitride (AlN) and aluminum oxide (Al2O3) on the stoichiometry, chemical bonding, and morphology of GaN thin films were determined with X-ray photoelectron spectroscopy (XPS), high-resolution x-ray diffraction (HRXRD), and atomic force microscopy (AFM). Scanning and transmission electron microscopy of coated silica nanosprings were compared with corresponding data for the GaN thin films. As grown, GaN on NS is conformal and amorphous. Upon introducing buffer layers of Al2O3 or AlN or combinations thereof, GaN is nanocrystalline with an average crystallite size of 11.5 ± 0.5 nm. The electrical properties of the GaN coated NS depends on whether or not a buffer layer is present and the choice of the buffer layer. In addition, the IV curves of GaN coated NS and the thin films (TF) with corresponding buffer layers, or lack thereof, show similar characteristic features, which supports the conclusion that atomic layer deposition (ALD) of GaN thin films with and without buffer layers translates to 1D nanostructures.

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Lyutovich, Klara, Erich Kasper, Michael Oehme, Jens Werner, and Tatiana S. Perova. "Strained Silicon on Ultrathin Silicon-Germanium Virtual Substrates." Solid State Phenomena 108-109 (December 2005): 463–68. http://dx.doi.org/10.4028/www.scientific.net/ssp.108-109.463.

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Molecular beam epitaxy is employed for the growth of strained-Si layers on top of virtual substrates with highly-relaxed ultrathin SiGe buffers in a continuous procedure. An initial growth stage at a temperature-ramp down to below 200°C causes misfit-dislocation generation by nucleation from point defects and provides an early relaxation in the SiGe buffers. In situ monitoring is used for the growth control. Layer thicknesses and composition are proved by ex situ spectroscopic ellipsometry. %Raman investigations on the layer stacks reveal high degrees of relaxation (70-100%) in sub-100nm SiGe buffer layers containing from 12 to 42 % Ge. Stress in strained Si layers estimated by means of Raman-spectra shift is adjustable from 0.92 to 6.84 GPa by the Ge-content in virtual substrates. Surface morphology of strained Si and of relaxed SiGe buffers is smooth and crosshatch-free. Device test structures show substantial increase of carrier mobilities in nMOSFETs fabricated on these strained-Si layers.

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Paulauskas, T., J. Devenson, S. Stanionytė, M. Skapas, V. Karpus, B. Čechavičius, S. Tumėnas, V. Strazdienė, B. Šebeka, and V. Pačebutas. "Epitaxial growth of GaAsBi on thin step-graded InGaAs buffer layers." Semiconductor Science and Technology 37, no. 6 (April 19, 2022): 065004. http://dx.doi.org/10.1088/1361-6641/ac61ff.

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Abstract Molecular beam epitaxy growth and analysis of GaAsBi on compositional step-graded InGaAs buffer layers are presented in this study. The developed buffer is only 240 nm thick, exhibits very low surface roughness while reaching up to 0.46% lattice-mismatch with a GaAs substrate. Reciprocal-space mappings showed that 500 nm thick GaAsBi layers with 2.7%–5.3% Bi remain pseudomorphic with the InGaAs buffer, in contrast to GaAsBi grown on GaAs that were found to incur up to 50% lattice relaxation. CuPtB-type ordering and associated polarized photoluminescence were also found in the bismide layers grown on the InGaAs buffers. Optical anisotropy of a strain-free 2.7% Bi GaAsBi was further analysed by a suite of optical techniques indicating that the valence band splitting is ∼40 meV. This study advances synthesis techniques of thick GaAsBi layers for optoelectronic device applications.

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30

Jiang, Hai Yun, De Jian Zhao, Wei Li Zhang, Ruo Mei Wu, and Bao Feng Song. "Some Observations on Dynamical Cushioning Property of Overlay Cushion Combined with Dissimilar Materials." Applied Mechanics and Materials 200 (October 2012): 122–25. http://dx.doi.org/10.4028/www.scientific.net/amm.200.122.

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Honeycomb fiberboard, polyethylene foam, and polystyrene foam were used to manufacture overlay cushion. The corresponding dynamical cushioning property was investigated including the effects the overlay sequence, drop height, join mode, and the thickness difference of both buffer layers. The results indicated the overlay cushion kept a relative high cushioning property when the “soft” buffer layer was directly contacted with the impact rammer. However, the result may be in reverse without adhesion. At the same time, the excessive difference of cushioning property between both the buffer layers was not beneficial to exertion of overlay cushion. Besides, this difference would be scaled up with increase of thickness difference of both the buffer layers.

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31

Zyoud, Samer H., Ahed H. Zyoud, Naser M. Ahmed, and Atef F. I. Abdelkader. "Numerical Modelling Analysis for Carrier Concentration Level Optimization of CdTe Heterojunction Thin Film–Based Solar Cell with Different Non–Toxic Metal Chalcogenide Buffer Layers Replacements: Using SCAPS–1D Software." Crystals 11, no. 12 (November 25, 2021): 1454. http://dx.doi.org/10.3390/cryst11121454.

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Cadmium telluride (CdTe), a metallic dichalcogenide material, was utilized as an absorber layer for thin film–based solar cells with appropriate configurations and the SCAPS–1D structures program was used to evaluate the results. In both known and developing thin film photovoltaic systems, a CdS thin–film buffer layer is frequently employed as a traditional n–type heterojunction partner. In this study, numerical simulation was used to determine a suitable non–toxic material for the buffer layer that can be used instead of CdS, among various types of buffer layers (ZnSe, ZnO, ZnS and In2S3) and carrier concentrations for the absorber layer (NA) and buffer layer (ND) were varied to determine the optimal simulation parameters. Carrier concentrations (NA from 2 × 1012 cm−3 to 2 × 1017 cm−3 and ND from 1 × 1016 cm−3 to 1 × 1022 cm−3) differed. The results showed that the use of CdS as a buffer–layer–based CdTe absorber layer for solar cell had the highest efficiency (%) of 17.43%. Furthermore, high conversion efficiencies of 17.42% and 16.27% were for the ZnSe and ZnO-based buffer layers, respectively. As a result, ZnO and ZnSe are potential candidates for replacing the CdS buffer layer in thin–film solar cells. Here, the absorber (CdTe) and buffer (ZnSe) layers were chosen to improve the efficiency by finding the optimal density of the carrier concentration (acceptor and donor). The simulation findings above provide helpful recommendations for fabricating high–efficiency metal oxide–based solar cells in the lab.

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Hoai Nam, Nguyen Phuong. "Enhanced Performance in Polymer Light Emmiting Diode by Using Ultra-thin Conductive Films as the Buffer Layer." Communications in Physics 24, no. 3S1 (October 10, 2014): 7–12. http://dx.doi.org/10.15625/0868-3166/24/3s1/5071.

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The ultra-thin nanocomposite films based on the nano-crystal TiO$_{2}$ (TiO$_{2}$-nc) or multi-walled carbon nano-tube (MWCNTs) were prepared and used as the buffer layers in the fabrication of the organic light-emitting diodes (OLEDs). The injection efficiency of the hole and electron was improved by inserting an ultra-thin buffer layer between the electrodes and emissive layer. The turn-on voltage of the device with the buffer layers was lowered from 4 to 2.5V, and the current density was increased from 0.3 to 0.7~mA/mm$^{2}$, in comparison with the device without such a buffer layer. These devices showed a high efficiency and good stability.

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33

PYSARENKO, S. V., A. V. PAN, S. DOWNING, and S. X. DOU. "DEVELOPMENT OF MULTILAYER COATED CONDUCTORS WITH SIMPLIFIED BUFFER STRUCTURE." International Journal of Modern Physics B 23, no. 17 (July 10, 2009): 3526–31. http://dx.doi.org/10.1142/s0217979209062918.

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The quality superconducting YBa 2 Cu 3 O 7 films and YBa 2 Cu 3 O 7/ NdBa 2 Cu 3 O 7 multilayered film structures have been grown by pulsed laser deposition on metallic templates with magnesium oxide (MgO) buffer layer grown by incline substrate deposition. Different supplementary buffer layers have been deposited between the superconductor and MgO buffer layer. This additional buffer layer reduces the crystal structure misalignment of the superconducting layers. The critical current density has been observed to be higher in the multilayered structures in comparison with the same thickness of monolayer YBa 2 Cu 3 O 7 films. The origin of this enhancement is the improved microstructure of the multilayered systems obtained.

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34

Lungu, Jeanina, Gabriel Socol, George E. Stan, Nicolaie Ştefan, Cătălin Luculescu, Adrian Georgescu, Gianina Popescu-Pelin, Gabriel Prodan, Mihai A. Gîrţu, and Ion N. Mihăilescu. "Pulsed Laser Fabrication of TiO2 Buffer Layers for Dye Sensitized Solar Cells." Nanomaterials 9, no. 5 (May 15, 2019): 746. http://dx.doi.org/10.3390/nano9050746.

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We report on the fabrication of dye-sensitized solar cells with a TiO2 buffer layer between the transparent conductive oxide substrate and the mesoporous TiO2 film, in order to improve the photovoltaic conversion efficiency of the device. The buffer layer was fabricated by pulsed laser deposition whereas the mesoporous film by the doctor blade method, using TiO2 paste obtained by the sol–gel technique. The buffer layer was deposited in either oxygen (10 Pa and 50 Pa) or argon (10 Pa and 50 Pa) onto transparent conducting oxide glass kept at room temperature. The cross-section scanning electron microscopy image showed differences in layer morphology and thickness, depending on the deposition conditions. Transmission electron microscopy studies of the TiO2 buffer layers indicated that films consisted of grains with typical diameters of 10 nm to 30 nm. We found that the photovoltaic conversion efficiencies, determined under standard air mass 1.5 global (AM 1.5G) conditions, of the solar cells with a buffer layer are more than two times larger than those of the standard cells. The best performance was reached for buffer layers deposited at 10 Pa O2. We discuss the processes that take place in the device and emphasize the role of the brush-like buffer layer in the performance increase.

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35

Tang, Wu, Yi Peng Chao, Yong Si Fang, Xiao Long Weng, and Long Jiang Deng. "Influence of Al₂O₃ Buffer Layers on the Properties of Indium–Tin Oxide Films on PET Substrate by RF-Magnetron Sputtering." Materials Science Forum 675-677 (February 2011): 1209–12. http://dx.doi.org/10.4028/www.scientific.net/msf.675-677.1209.

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Indium Tin Oxide (ITO) films on PET substrate sandwiching Al2O3 buffer layers with different thickness have been prepared by magnetron sputtering at low deposition temperature. The crystal structures, electrical and optical properties of ITO films have been investigated by XRD, four-point probe technology and UV-Vis spectrophotometer as a function of different Al2O3 buffer layers thickness, respectively. XRD reveals that there is an amorphous structure in ITO films with no buffer layer. However, ITO films became crystalline after sandwiching the buffer layer. It can be found that there are two major peaks, (222) and (400) of ITO film. A smallest resistivity of 3.53×10-4 Ω.cm was obtained for ITO film with Al2O3 buffer layers thickness 75nm. The average transmittance of ITO/Al2O3/PET films in the visible range of 400-760nm wavelength was around 80%. It can be conclude that the (222) orientation of ITO film is more in favor of low resistivity.

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36

Lee, H. J., S. W. Lee, H. Goto, Hyo-Jong Lee, J. S. Ha, M. W. Cho, and T. Yao. "Free standing GaN layers with GaN nanorod buffer layer." physica status solidi (c) 4, no. 7 (June 2007): 2268–71. http://dx.doi.org/10.1002/pssc.200674858.

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37

Zaumseil, P., A. Giussani, O. Seifarth, Tzanimir Arguirov, M. A. Schubert, and T. Schroeder. "Characterization of Semiconductor Films Epitaxially Grown on Thin Metal Oxide Buffer Layers." Solid State Phenomena 156-158 (October 2009): 467–72. http://dx.doi.org/10.4028/www.scientific.net/ssp.156-158.467.

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Silicon and germanium films epitaxially grown on metal oxide buffer layers on Si(111) substrates are characterized by different X-ray techniques, transmission electron microscopy and Raman spectroscopy. Pr2O3 and Y2O3 or a combination of both is used as buffer material. X-ray pole figure measurements and grazing incident X-ray diffraction prove that epi-semiconductor layers can be grown single crystalline with exactly the same in-plane orientation as the Si(111) substrate. Epi-Ge layers show a small fraction (less than 0.5 vol. %) of so-called type B rotation twin regions located near the oxide-Ge interface. The main structural defects for both epi materials are micro twin lamellas lying in {111} planes 70° inclined to the wafer surface that may reach through the whole layer from the oxide interface to the surface. Furthermore, TEM confirms the existence of stacking faults and threading dislocations. X-ray grazing incident diffraction and Raman measurements show that epi-Ge layers on Pr2O3 buffer are nearly fully relaxed, while epi-Si layers on Y2O3/Pr2O3 double buffer are compressive strained depending on their own thickness and the thickness of the underlying Y2O3 layer. It is demonstrated that the epi-layer quality can be improved by post-deposition annealing procedures.

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38

YANG, J., H. Z. LIU, H. ZHANG, F. QU, Q. ZHOU, and H. W. GU. "SURFACE MORPHOLOGY AND MICROSTRUCTURE OF DIRECT CURRENT SPUTTERING GROWTH OF BUFFER LAYERS FOR YBCO COATED CONDUCTOR." International Journal of Modern Physics B 21, no. 18n19 (July 30, 2007): 3348–51. http://dx.doi.org/10.1142/s0217979207044536.

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A composite buffer of CeO 2/ YSZ / Y 2 O 3 was investigated on the biaxially textured NiW long tape for YBCO coated conductor with magnetron sputtering technique. Every layer's surface morphology was observed by scanning electron microscopy. The seed layer Y 2 O 3 film was full coverage of the NiW substrate. The cap layer CeO 2 showed a smooth and crack-free surface and good crystallinity. The roughness of CeO 2 surface was measured by atom force microscopy. The transmission electron microscopy was used to analyze the cross-section of buffer layers and YBCO layer.

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39

Kujofsa, Tedi, and John E. Ayers. "Equilibrium Lattice Relaxation and Misfit Dislocations in Continuously- and Step-Graded InxGa1-xAs/GaAs (001) and GaAs1-yPy/GaAs (001) Metamorphic Buffer Layers." International Journal of High Speed Electronics and Systems 24, no. 03n04 (September 2015): 1520009. http://dx.doi.org/10.1142/s0129156415200098.

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The inclusion of metamorphic buffer layers (MBL) in the design of lattice-mismatched semiconductor heterostructures is important in enhancing reliability and performance of optical and electronic devices. These metamorphic buffer layers usually employ linear grading of composition, and materials including InxGa1-xAs and GaAs1-yPy have been used. Non-uniform and continuously graded profiles are beneficial for the design of partially-relaxed buffer layers because they reduce the threading dislocation density by allowing the distribution of the misfit dislocations throughout the metamorphic buffer layer, rather than concentrating them at the interface where substrate defects and tangling can pin dislocations or otherwise reduce their mobility as in the case of uniform compositional growth. In this work we considered heterostructures involving a linearly-graded (type A) or step-graded (type B) buffer layer grown on a GaAs (001) substrate. For each structure type we present minimum energy calculations and compare the cases of cation (Group III) and anion (Group V) grading. In addition, we studied the (i) average and surface in-plane strain and (ii) average misfit dislocation density for heterostructures with various thickness and compositional profile. Moreover, we show that differences in the elastic stiffness constants give rise to significantly different behavior in these two commonly-used buffer layer systems.

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40

Mesa, Fredy, William Chamorro, William Vallejo, Robert Baier, Thomas Dittrich, Alexander Grimm, Martha C. Lux-Steiner, and Sascha Sadewasser. "Junction formation of Cu3BiS3 investigated by Kelvin probe force microscopy and surface photovoltage measurements." Beilstein Journal of Nanotechnology 3 (March 23, 2012): 277–84. http://dx.doi.org/10.3762/bjnano.3.31.

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Recently, the compound semiconductor Cu3BiS3 has been demonstrated to have a band gap of ~1.4 eV, well suited for photovoltaic energy harvesting. The preparation of polycrystalline thin films was successfully realized and now the junction formation to the n-type window needs to be developed. We present an investigation of the Cu3BiS3 absorber layer and the junction formation with CdS, ZnS and In2S3 buffer layers. Kelvin probe force microscopy shows the granular structure of the buffer layers with small grains of 20–100 nm, and a considerably smaller work-function distribution for In2S3 compared to that of CdS and ZnS. For In2S3 and CdS buffer layers the KPFM experiments indicate negatively charged Cu3BiS3 grain boundaries resulting from the deposition of the buffer layer. Macroscopic measurements of the surface photovoltage at variable excitation wavelength indicate the influence of defect states below the band gap on charge separation and a surface-defect passivation by the In2S3 buffer layer. Our findings indicate that Cu3BiS3 may become an interesting absorber material for thin-film solar cells; however, for photovoltaic application the band bending at the charge-selective contact has to be increased.

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41

Zheng, Chang Da, Li Wang, Wen Qing Fang, and Feng Yi Jiang. "Growth of ZnO Films on Si(111) by Metalorganic Chemical Vapor Deposition with AlN and Low-Temperature ZnO Double Buffers." Advanced Materials Research 652-654 (January 2013): 594–98. http://dx.doi.org/10.4028/www.scientific.net/amr.652-654.594.

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To enhance the quality of ZnO films on Si(111) substrate, single layers of low-temperature ZnO (LT-ZnO) and AlN, as well as a combination of AlN and LT-ZnO layer, were used as intermediate layers by atmospheric pressure metalorganic chemical vapor deposition system. Only polycrystalline ZnO film was formed when a LT-ZnO single buffer was used. Crystal quality was enhanced when LT-ZnO was replaced by 20 nm AlN as the single buffer. The full width at half maximum (FWHM) of ZnO(0002) x-ray diffraction ω-rocking curve was 642 arcsec. Cracks began to appear on the film surface as crystallinity was enhanced. A ZnO mosaic single-crystal film with a mirror-like surface was successfully fabricated when a combined AlN and LT-ZnO served as buffer, and its FWHM of ZnO(0002) ω-rocking curve peak was only 460 arcsec. The film surface was smoother but cracks were still evident on the film. Contrary to the three-dimensional growth mode of samples with a single buffer, a quasi-two-dimensional growth mode was realized for the double-buffered high-temperature ZnO layer. Calculated film thickness was 2.14 μm, and the growth rate reached 4.3 μm/h based on the laser in situ laser reflectance trace.

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42

Nakatsuka, Osamu, Shotaro Takeuchi, Yosuke Shimura, Akira Sakai, and Shigeaki Zaima. "Strained Ge and Ge_1-xSn_x Technology for Future CMOS Devices." Key Engineering Materials 470 (February 2011): 146–51. http://dx.doi.org/10.4028/www.scientific.net/kem.470.146.

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We have investigated the growth and crystalline structures of Ge1-xSnx buffer and tensile-strained Ge layers for future use in CMOS technology. We have demonstrated that strain relaxed Ge1-xSnx layers with an Sn content of 12.3% and 9.2% can be grown on Ge and Si substrates, respectively. We achieved a tensile-strain value of 0.71 % in Ge layers on a Ge0.932Sn0.068 buffer layer. We have also investigated the effects of Sn incorporation into Ge on the electrical properties of Ge1-xSnx heteroepitaxial layers.

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43

Ballingall, J. M., Pin Ho, R. P. Smith, S. Wang, G. Tessmer, T. Yu, Ernest L. Hall, and Gudrun Hutchins. "Material and Device Characteristics of MBE Microwave Power FETs with Buffer Layers Grown at Low Temperature (300°C)." MRS Proceedings 241 (1991). http://dx.doi.org/10.1557/proc-241-171.

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ABSTRACTMBE GaAs grown at low temperature (300°C) is evaluated for its suitability as a buffer layer for microwave power FETs. Hall effect and capacitance-voltage (C-V) measurements show that low temperature (LT) buffers may have strong deleterious effects on the electronic quality of FET active layers unless they are heat-treated in-situ at 600'C and topped with a thin (∼0. lμm) 600°C GaAs buffer prior to growth of the FET active layer. The voltage isolation properties of the LT buffers are found to be thermally stable to rapid thermal anneals up to 870°C for 10 seconds.Transmission electron microscopy (TEM) cross-sections were examined on FET layers with LT buffer layers which ranged in thickness from 0.1μm to 1.0μm. The TEM reveals a high density (∼1017 cm−3) of small (<100Å) arsenic precipitates in all of the buffer layers studied. In cases where the LT buffer is not heat treated and topped with a thin 600°C GaAs buffer layer, dislocations and arsenic precipitates extend from the buffer layer into the FET active layer. Their presence in the active layer correlates with the degradation in electronic properties observed with Hall effect and CV. Microwave power FETs were measured at DC and 5 GHz. DC and RF results for devices with LT buffer layers are comparable to devices with conventional buffer layers.

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44

Yun, Feng, Michael A. Reshchikov, Paolo Visconti, Keith M. Jones, Dongfeng Wang, Marc Redmond, Jie Cui, Cole W. Litton, and Hadis Morkoç. "Investigation of Buffer Layers for GaN Grown by MBE." MRS Proceedings 639 (2000). http://dx.doi.org/10.1557/proc-639-g3.17.

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ABSTRACTThe structural quality of the buffer layer juxtaposed to the substrate is pivotal in attaining high quality GaN layers. In MBE deposition, low temperature, medium temperature and high temperature AlN buffer layers are at the disposal of the grower. There are quite a few reports, some discussing the benefits of high temperature buffer layers and others doing the same for low temperature buffer layers. The reports emanate from different laboratories; and due to stringent parameter control required, it is difficult to compare one type of buffer with another. To gain some insight, we undertook an investigation wherein these varieties of buffer layers were grown on nitridated sapphire substrate under similar conditions for a comparative analysis. In addition to the single buffer layers of both GaN and AlN varieties, some combinations of stacked buffer layers, including cases where these buffer layers were separated by GaN layers, were employed. Structural analysis by high resolution X-ray diffractometry and topological analysis by AFM were carried out to assess the quality of the epilayers grown on these buffers. Hall measurements at room temperature were carried out to characterize the electrical transport properties.

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45

Bowman, R. C., P. M. Adams, C. C. Ahn, S. J. Chang, V. Arbet, and K. L. Wang. "Structural Characterizations of Symmetrically Strained Sim Gen Superlattices." MRS Proceedings 160 (1989). http://dx.doi.org/10.1557/proc-160-101.

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AbstractMolecular beam epitaxy was used to grow Sim Gen superlattices on relaxed Si1-xGex buffer layers which symmetrize the strains between the heteroepitaxial layers. Samples with different superlattïce periodicities and individual layer thickness ratios were prepared. The compositions and defect structures of the GexSi1-x buffers have significant influence on the homogeneity and quality of the overlying superlattices. In particular, greater disorder was found in superlattice structures grown on Si0.5 Ge0.5 buffers than for those grown on buffer layers with significantly higher or lower Ge contents.

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46

Platzer-Bjöerkman, Charlotte, and Alexander Uhl. "Comparison of ZnS-based Buffer Layers by Chemical Bath Deposition and Atomic Layer Deposition." MRS Proceedings 1165 (2009). http://dx.doi.org/10.1557/proc-1165-m05-02.

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AbstractIn this work we compare ZnS-based buffer layers prepared by atomic layer deposition, ALD, and chemical bath deposition, CBD. Both material and device properties are compared. CBD buffer layers are amorphous with a Zn(OH,S) composition while ALD buffer layers used in devices are crystalline with a Zn(O,OH,S) composition. Devices with ALD buffer layers are stable while for CBD, large lightsoaking effects are seen. Stable devices with CBD buffer layers are obtained by including an ALD-(Zn,Mg)O layer on top of the CBD layer.

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47

Al-Allak, H. M., A. W. Brinkman, P. A. Clifton, and P. D. Brown. "The Epitaxial Growth by Movpe of (Hg,Mn)Te On (001) Gaas Substrates." MRS Proceedings 216 (1990). http://dx.doi.org/10.1557/proc-216-35.

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ABSTRACTEpitaxial thin films of the dilute magnetic semiconductor Hg1-xMnxTe have been grown by MOVPE on (100) GaAs substrate with or without buffer layers. Deposition took place in a horizontal, atmospheric pressure reactor at temperatures in the range 350–400° C, using tricarbonyl (methyl cyclopentadienyl) manganese, di-isopropyl tellurium and elemental mercury. Buffer layers consisted of thin layers of ZnTe and an upper thick layer (∼1μm) of CdTe. The good crystallinity was confirmed by RHEED and double crystal x-ray diffraction with rocking curve widths of 500–600 arc. sec. for non-buffered layers, and 315 arc. sec. for buffered layers. TEM investigations show that layers grown on buffered substrates had improved microstructure defect content. Electrical transport measurements revealed that as-grown layers were ptype with Hall mobilities in excess of 0.1 m2V−1s−1.

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Namkoong, Gon, W. Alan, A. S. Brown, M. Losurdo, M. M. Giangregorio, and G. Bruno. "Effect of Buffer Design on AlGaN/AlN/GaN Heterostrucutres by MBE." MRS Proceedings 798 (2003). http://dx.doi.org/10.1557/proc-798-y10.62.

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ABSTRACTThe effect of the buffer layers on the subsequent GaN epitaxial layers and electrical properties of AlGaN/AlN/GaN heterojunction structures nitrided at various temperatures was investigated. For AlN buffer layers, two different growth conditions of AlN buffer layers were introduced to avoid Al droplets. We found that etch pit density and structural quality of GaN epitaxial layer strongly depends on the growth conditions of AlN buffer layers. When using a double buffer layer (low temperature GaN on high temperature AlN) for 200 °C nitridation, the etch pit density was measured to high 107 cm-2 in GaN epitaxial layers. Furthermore, we observed that electrical properties of AlGaN/AlN/GaN heterostructures depend on growth conditions of buffer layers and nitridation temperatures. The mobility in Al0.33Ga0.67N/AlN/GaN structures grown on single AlN buffer layers for 200 °C nitridation were 1300 cm2/Vs at a sheet charge of 1.6×1013 cm-2. Using the double buffer layer for 200 °C nitridation, the mobility increased to 1587 cm2/Vs with a sheet charge of 1.25×1013 cm-2.

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Piquette, E. C., P. M. Bridger, R. A. Beach, and T. C. McGill. "Effect of Buffer Layer and III/V Ratio on the Surface Morphology of Gan Grown by MBE." MRS Proceedings 537 (1998). http://dx.doi.org/10.1557/proc-537-g3.77.

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AbstractThe surface morphology of GaN is observed by atomic force microscopy for growth on GaN and AlN buffer layers and as a function of III/V flux ratio. Films are grown on sapphire substrates by molecular beam epitaxy using a radio frequency nitrogen plasma source. Growth using GaN buffer layers leads to N-polar films, with surfaces strongly dependent on the flux conditions used. Flat surfaces can be obtained by growing as Ga-rich as possible, although Ga droplets tend to form. Ga-polar films can be grown on AlN buffer layers, with the surface morphology determined by the conditions of buffer layer deposition as well as the III/V ratio for growth of the GaN layer. Near-stoichiometric buffer layer growth conditions appear to support the flattest surfaces in this case. Three defect types are typically observed in GaN films on AlN buffers, including large and small pits and “loop” defects. It is possible to produce surfaces free from large pit defects by growing thicker films under more Ga-rich conditions. In such cases the surface roughness can be reduced to less than l nm RMS.

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Chen, E., J. S. Ahearn, K. Nichols, P. Uppal, and D. C. Paine. "Tem Investigation of Al0.5Ga0.5As1-y Sby Buffer Layer Systems." MRS Proceedings 484 (1997). http://dx.doi.org/10.1557/proc-484-31.

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AbstractWe report on a TEM study of Sb-adjusted quaternary Al0.5Ga0.5As1-y Sby buffer-layers grown on <001> GaAs substrates. A series of structures were grown by MBE at 470°C that utilize a multilayer grading scheme in which the Sb content of Al0.5Ga0.5As1-ySby is successively increased in a series of eight 125 nm thick layers. Post growth analysis using conventional bright field and weak beam dark field imaging of these buffer layers in cross-section reveals that the interface misfit dislocations are primarily of the 60° type and are distributed through out the interfaces of the buffer layer. Plan view studies show that the threading dislocation density in the active regions of the structure (approximately 2 μm from the GaAs substrate) is 105–6/cm2 which is comparable to equivalent InxGa1−x As buffers. Weak Sb-As compositional modulations with a period of 1.8 nm were observed that provide a marker for establishing the planarity of the growth process. These features reveal that the growth surface remains planar through out the buffer layer growth sequence.

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Journal articles on the topic 'Buffer layers'

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