Akira Bandoh

Microstructure of epitaxial lateral overgrown AlN on trench-patterned AlN template by high-temperature metal-organic vapor phase epitaxy

A high-quality thick AlN layer without cracks was grown on sapphire by the combination of the high-temperature metal-organic vapor phase epitaxial growth and epitaxial lateral overgrowth methods. The dislocation behavior and growth mode of AlN are investigated in detail. The dislocation density of the AlN layer thus grown was less than 107cm−2.

High-Temperature Metal-Organic Vapor Phase Epitaxial Growth of AlN on Sapphire by Multi Transition Growth Mode Method Varying V/III Ratio

High-quality AlN layers were grown on c-plane sapphire substrates by high-temperature metal-organic vapor phase epitaxy. AlN layers of about 9 µm in thickness with an atomically flat surface were obtained without cracks. Multiple modulation of the V/III ratio during growth led to a reduction in the number of dislocations during the growth transition period. The dislocation density of the AlN layers was found to be less than 3×108 cm-2.

Dislocations in AlN Epilayers Grown on Sapphire Substrate by High-Temperature Metal-Organic Vapor Phase Epitaxy

The growth temperature of AlN layers is one of the most important factors in metal-organic vapor phase epitaxy (MOVPE) growth. AlN layers were grown using our customized high-temperature MOVPE system. The crystalline quality was discussed on the basis of X-ray diffraction, atomic force microscopy (AFM) and transmission electron microscopy (TEM) measurements. The samples grown at a temperature of 1400 °C had much improved crystalline quality in terms of the X-ray rocking curve full width at half maximum values and AFM root-mean-square roughness. In addition, according to TEM analysis, edge type dislocations caused by small-angle grain boundaries were predominant under a low growth temperature, whereas these dislocations became much fewer with increasing growth temperature.

Influence of High Temperature in the Growth of Low Dislocation Content AlN Bridge Layers on Patterned 6H-SiC Substrates by Metalorganic Vapor Phase Epitaxy

A novel high temperature metalorganic vapor phase epitaxy (MOVPE) growth of AlN bridge layer is reported. Positive influence of high temperature on the growth rate and reduction of dislocation content in the AlN bridge layer has been observed. Transmission electron microscopy, X-ray diffraction, and atomic force microscopy analyses confirmed that the layer had high structural quality and smooth morphology.

Thermodynamic Aspects of Growth of AlGaN by High-Temperature Metal Organic Vapor Phase Epitaxy

The metalorganic vapor phase epitaxial (MOVPE) growth of AlGaN on AlN-coated sapphire at a temperature higher than 1,200 °C was carried out. Compared with that at a low-temperature growth regime in which alloy composition is determined by the flow rates of metalorganic Ga and Al sources, the solid composition of AlGaN is found to be strongly affected by thermodynamics.

Growth of GaInN by Raised-Pressure Metalorganic Vapor Phase Epitaxy

GaInN films with different In compositions were grown using a raised-pressure metalorganic vapor phase epitaxy (MOVPE) system operated from 100 to 200 kPa. A precise X-ray diffraction study showed that the In composition increases with an increasing pressure during growth, which is consistent with the result of a thermodynamic analysis.

Step-Bunching Dependence of the Lifetime of MOS Capacitor on 4o Off-Axis Si-Face 4H-SiC Epitaxial Wafers

The step-bunching dependence of the lifetime of metal–oxide–semiconductor capacitors on 4° off-axis 4H-SiC epitaxial wafers was investigated. The effects of the C/Si ratios in epitaxial growth and the substrate properties were examined. Step-bunching was observed at the base of triangle or trapezoid defects. Step-bunching decreased as the C/Si ratio was reduced. Time-dependent dielectric breakdown (TDDB) measurements showed that the locations of short lifetime breakdowns closely matched step-bunching positions. TDDB measurements of four different commercial substrates showed clear differences in capacitor lifetime.

High-quality 100/150 mm p-type 4H-SiC epitaxial wafer for high-voltage bipolar devices

This paper presents a high-quality 100/150 mm p-type 4H-SiC epitaxial wafer prepared by chemical vapor deposition; this wafer is suitable for high-voltage bipolar device applications. The density of killer defects for bipolar devices including downfalls, triangular-shaped defects, and basal plane dislocations (BPDs), is less than 0.1 cm-2 in the proposed 100 mm n/p multilayer epitaxial wafer. The in-plane thickness and doping uniformity of the 150 mm p-layer is 3.0% and 11.0%, respectively. The doping concentration of the p-layer can be controlled in the 1E+16 cm-3 to 1E+19 cm-3 range.

Comparison of the simulation and experiments of the nitride-based UV light emitting diodes

In attempt to prepare a high performance AlxGa1-xN based UV-B LED, a computer simulation has been performed on a typical UV-LED structure to find out the effect of threading dislocations on non-radiative recombination process. UVB LED structures were formed on using GaN and AlN based layers for comparison. Cracks were generated in the device structure formed on GaN underlayer. No cracks were observed on the device structure formed on AlN under layer. Much better structure was formed when the base AlN was grown by high temperature MOVPE.

Depth profile of doping concentration in thick (> 100 μm) and low-doped ( 14 cm −3 ) 4H-SiC epilayers

The depth profiles of n-type doping concentration in thick (>100 μm) and low-doped (< 4 × 1014 cm-3) 4H-SiC epilayers grown by chemical vapor deposition (CVD) were investigated. The variation in doping concentration during epitaxial growth are considered to be caused by: (1) variation in gas flow due to parasitic deposition, (2) variation in precursor decomposition rate due to change in reactor temperature, (3) variation in dopant incorporation rate due to change in wafer temperature, and (4) variation in supply of background dopants. By controlling all these parameters, a constant depth profile in thick (> 100um) epilayers was realized.