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Uniformity and repeatability of InAlN-barrier HEMTs growth by high-speed-rotation single-wafer MOCVD tool
摘要： We fabricated high-electron-mobility transistor structures with InAlN as a barrier layer on 8- or 6-inch Si substrates by using a recently developed high-speed-wafer-rotation single-wafer MOCVD tool. It has been reported that Ga inclusion in the InAlN layer causes serious problems in the control of group III metal composition in some cases, but the samples grown using the tool exhibited an InAlN layer with an abrupt interface and almost no Ga inclusion. Excellent in-wafer uniformity, repeatability, and wafer-to-wafer uniformity of device structure are also reported. The results shown in this paper indicate high performance of the tool in the real production of devices.
关键词： A3. Metalorganic vapor phase epitaxy,B1. Nitrides,B2. Semiconducting III-V materials,B3. High electron mobility transistors
更新于2025-09-23 15:23:52
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High throughput MOVPE and accelerated growth rate of GaAs for PV application
摘要： We present the feasibility of metalorganic vapor phase epitaxy (MOVPE) with extremely high-speed growth of GaAs for solar cell applications. The growth rate was increased up to 120 μm/h, and exhibited an almost linear relationship with the amount of supplied trimethylgallium (TMGa). The thickness variation and doped carrier concentration of GaAs grown at 90 μm/h were comparable to those of conventionally grown GaAs at a lower growth rate. The potential for reducing the V/III supply ratio was investigated to reduce the material cost. Non-doped GaAs wafers were grown at the accelerated growth rate of 90 μm/h, with various V/III ratios. The growth rate of GaAs increased by 20% when the V/III ratio was decreased from 40 to 5. In low temperature photo-luminescence (PL) measurement, significant change in PL spectra was not observed, indicating that there was no significant change in quality. The light-power conversion efficiency was almost comparable for V/III ratios from 10 to 40 whereas that at the lowest V/III ratio of 5 was degraded. Photovoltaic (PV) solar cells of GaAs were fabricated with various growth condition. It is found that the performance of the cells grown at 90 μm/h were comparable with previous results.
关键词： A3. Metalorganic vapor phase epitaxy,B2. Semiconducting GaAs,B3. Solar cells,A1. Crystal morphology
更新于2025-09-23 15:23:52
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Morphological study of InGaN on GaN substrate by supersaturation
摘要： The morphology of thin InGaN layers grown on c-plane GaN substrates by metalorganic vapor phase epitaxy (MOVPE) has been studied by atomic force microscopy. Three different morphologies appeared, a stepped surface, large flat two-dimensional (2D) islands and small high three-dimensional (3D) dots. Low growth temperature and high growth rate (i.e. increased vapor supersaturation) changed the InGaN morphology from steps to 2D islands and then 3D dots (when exceeding the critical thickness for 3D dots). Larger miscut angle of GaN substrate changed the morphology from 2D islands to step by decreasing the surface supersaturation of individual terraces. InGaN layers with a stepped morphology had the highest internal quantum efficiency at similar InN mole fraction. InGaN grown on GaN substrate more easily achieved a stepped morphology compared to InGaN on GaN/sapphire templates.
关键词： A3. Metalorganic vapor phase epitaxy,B2. Semiconducting III-V materials,A1. Crystal morphology,B1. Nitride
更新于2025-09-23 15:22:29
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Improvement of electrical characteristics in regrown AlGaN/GaN MOSFETs by suppression of the residual interface charge
摘要： In this paper, the influence of a regrown interface on the electrical properties of AlGaN/GaN heterostructure was investigated for recessed-gate MOSFETs fabricated by selective area regrowth. The electron mobility of the two-dimensional electron gas (2DEG) on regrown AlGaN/GaN structures was degraded when the 2DEG was near the regrown interface. The regrown interface had high carrier concentrations and Si impurities that caused degradation of the electron mobility of the 2DEG. Unintentional carrier generation at the regrown interface was eliminated by ultraviolet (UV) treatment before regrowth. A regrown AlGaN/GaN MOSFET device was then fabricated using the UV treatment. The device exhibited good performance such as normally-off operation without hysteresis or leaks. Improvement of the electrical characteristics of AlGaN/GaN MOSFETs was thus achieved by suppression of regrown interface charge.
关键词： B2. Semiconducting gallium compounds,B3 High electron mobility transistors,A1. Interfaces,A3. Metalorganic vapor phase epitaxy,B1. Nitride
更新于2025-09-23 15:22:29
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Strain control of GaN grown on Si substrates using an AlGaN interlayer
摘要： To suppress wafer bowing and crack generation of GaN on Si substrates, we investigated the effects of the Al content and thickness of the AlGaN interlayer on the compressive strain in the overlying GaN layer theoretically and experimentally. In the simulation, AlGaN relaxes gradually over the critical thickness. Therefore, the relaxation ratio of AlGaN at the top surface can be defined as a function of Al content and thickness. Too high Al content or too thick AlGaN interlayer induced too large initial strain in the upper GaN layer, which caused rapid and succeeding gradual relaxation, i.e., decrease of strain, of the GaN layer during growth because of generation of threading dislocations. Conversely, low Al content or thin AlGaN interlayer could induce constant but only small strain in the GaN layer. Therefore, the ideal relaxation ratio of the AlGaN surface exists to apply the maximal constant compressive strain in the GaN layer. The relaxation ratios of AlGaN interlayers determined in experiments were much smaller than those calculated in the simulation. Although the measured compressive strain in the GaN layer was smaller than expected, its decrease rate was small when grown on AlGaN interlayers with an almost ideal relaxation ratio.
关键词： Computer simulation,Characterization,Metalorganic vapor phase epitaxy,Stresses,Growth models,Nitrides
更新于2025-09-23 15:22:29
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Effect of Buffer Layer Structure on the Structural Properties of GaAs Epitaxial Layers Grown on GaP Substrates
摘要： Three-μm-thick GaAs layers were grown on 2°-off (100) GaP substrates by employing various buffer layer structures, which consist of GaAsP- and InGaAs-based ternary compound semiconductors. To confirm the effects, we altered the layer thickness, the interface lattice mismatch, and number of the layers in the buffer layer structure, and also a superlattice structure was employed in some of the buffer layers. The lattice constants of the layers were controlled by changing the As/P and In/Ga compound ratios. The crystal properties of the grown GaAs layers were characterized with X-ray diffraction, photoluminescence, and etch pit density observations. The effect of the buffer layer structure on the crystallographic character of the GaAs layers was analyzed by introducing a parameter that is a function of the thickness and interface lattice mismatch of each layer in the buffer layer structure. The results suggest that the GaAs layer is relatively relaxed but contains a greater number of dislocations for smaller layer thicknesses and greater lattice mismatches in the buffer layer structure, while the GaAs layer has a smaller number of dislocations but a rather deformed lattice structure for larger layer thicknesses and smaller lattice mismatches. Our parameter is useful for developing design principles of buffer layer structures.
关键词： A3. Heteroepitaxial growth,B2. Semiconducting III-V materials,B3. Solar cells,A3. Metalorganic vapor phase epitaxy
更新于2025-09-23 15:21:01
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MOVPE growth of n-GaN cap layer on GaInN/GaN multi-quantum shell LEDs
摘要： Embedded growth of an n-GaN cap layer on multi-quantum shells (MQSs) and nanowires through a tunnel junction (TJ) was investigated for the improvement of current injection to the m-plane of the MQSs. Different growth conditions for an n-GaN cap layer were systematically studied to suppress Mg diffusion and void formation, which are serious problems in this structure. At a high temperature of 900 °C and above, the growth rate on a semi-polar r-plane decreased, and large voids were formed at the bottom part of the nanowires owing to the diffusion of Ga atoms from the r-plane to the m-plane. When the growth temperature decreased to 800 °C, the growth rate on both the m-plane and the r-plane increased, and the size of voids decreased. Simultaneously, Mg diffusion also disappeared because of the low growth temperature of 800 °C. It was found that the growth with an extremely low V/III ratio of 20 at low temperatures increases the lateral growth rate on the m-plane, and void formation is fully suppressed when the MQS height is 700 nm or less.
关键词： B1. Nitrides,A1. Nanostructures,B3. Laser diodes,A3. Metalorganic vapor phase epitaxy
更新于2025-09-23 15:19:57
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Highly tin doped GaAs at low growth temperatures using tetraethyl tin by metal organic vapor phase epitaxy
摘要： GaAs layers with a high tin (Sn) doping concentration and a smooth surface morphology were successfully grown at temperatures as low as 425 °C using tetraethyl tin (TESn) by metal organic vapor phase epitaxy (MOVPE). The samples grown at 650 °C showed Sn-rich droplets even with a low TESn molar flow rate of 0.06 μmol/min, indicating that Sn atoms were not incorporated into the GaAs film but segregated and accumulated on the film surface. Droplet formation was suppressed at a low growth temperature of 425 °C. This suggests that the segregation process is kinetically-limited, with the segregation mechanism is slow compared to the growth rate at low growth temperatures. Uncorrected Hall effect measurements found an electron concentration of ～1 × 1019 cm?3, which is close to the maximum reported doping-limit obtainable in GaAs:Sn grown by MOVPE, while avoiding droplet formation and maintaining a smooth surface morphology. The electron mobility is dominated by the ionized impurity scattering. The sample possesses a generally flat Sn profile extending from the substrate to the film surface. Secondary ion mass spectroscopy indicates that the Sn is electrically active but compensated by carbon acceptors to yield the measured carrier concentration.
关键词： A1. Segregation,B2. Semiconducting III-V materials,A1. Doping,A3. Metalorganic vapor phase epitaxy
更新于2025-09-19 17:15:36
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Room-temperature photoluminescence of AP-MOVPE grown single GaSb/GaAs quantum dot layer
摘要： The effect of GaAs host matrix on excitonic behaviour in AP-MOVPE grown GaSb/GaAs quantum dots (QDs) was investigated. Room temperature (RT) photoluminescence (PL) emission was achieved from single layers of quantum dots by controlling the GaAs host matrix growth temperature. Samples were prepared using a GaSb dot growth temperature of 530 °C, followed by growth of a thin GaAs ‘cold’ cap, before depositing the final part of the GaAs capping layer at either 550 °C, 600 °C or 650 °C. PL measurements at 10 K revealed QD emission peaks for all the samples at around 1.1 eV. However, variable temperature PL revealed different thermal quenching rates of the emission, with the rates of quenching reduced with increasing GaAs growth temperature. This was ascribed to reduced defect densities in GaAs grown at higher temperature, which resulted in QD emission even at RT. The hole localisation energy determined for these samples at RT was approximately 470 meV.
关键词： Defects,Antimonides,Metalorganic vapor phase epitaxy,Nanostructures,Gallium compounds
更新于2025-09-12 10:27:22
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Effect of gas phase temperature on InGaN grown by metalorganic vapor phase epitaxy
摘要： Wafer trays with different gaps (the distance between the top of the pocket and the bottom of the wafer) were used to grow InGaN/GaN multiple quantum wells (MQWs) in a horizontal metalorganic vapor phase epitaxy (MOVPE) reactor. The numerical reactor simulation revealed that at the similar surface temperature the gas phase temperature around the wafer increases due to an increased wafer tray temperature. This increased gas phase temperature is expected to increase the effective V/III ratio by enhanced NH3 decomposition. Photoluminescence (PL) intensities of long-wavelength MQWs increased at the same indium content by the enhanced gas phase temperature, while the emission became narrow. This is related to a smoother topography at higher gas phase temperatures.
关键词： A3. Metalorganic vapor phase epitaxy,B2. Semiconducting III-V materials,A1. Crystal morphology,B1. Nitride
更新于2025-09-04 15:30:14