Homoepitaxial Hydride Vapor Phase Epitaxy Growth on GaN Wafers Manufactured by the Na-Flux Method

Abstract

Homoepitaxial hydride vapor phase epitaxy (HVPE) growth on GaN substrates grown with a Na-flux method, which is the most promising approach for fabrication of large-diameter, low-dislocation-density, fast-growing GaN wafers, was attempted for the first time. We found that, when different growth methods are combined, the differences in oxygen concentrations between a seed and grown crystal must be eliminated to maintain the crystallographic quality of the seed. Two kinds of Na-flux-grown seed crystals were prepared; one had a surface composed of c, {101̅2}, and {101̅1} planes, the other a surface composed entirely of c-planes. Both crystals were sliced, ground, mirror-polished, and applied for 500-μm-thick HVPE growth. In the former sample, the seed crystal generated fine cracks, and the epitaxially grown layer had a rough surface and included many dislocations; the latter sample showed no fault. For clarifying the mechanism of crystal degradation, we investigated the lattice constants of each growth sector using an X-ray microbeam and found that lattice constants in the {101̅1}-growth sector were expanded compared to those in other growth sectors due to oxygen impurities. These values were estimated to be much larger than those of HVPE crystals, resulting in the crystal degradation after the HVPE growth by a lattice mismatch.

Terahertz time-domain ellipsometry with high precision for the evaluation of GaN crystals with carrier densities up to 1020 cm−3

“…Two free-standing GaN single crystals with different concentrations of oxygen impurities were investigated in this study. The first GaN sample (LPE-GaN) was grown on a GaN template using liquid phase epitaxy and has ~ 10 17 cm −3 oxygen concentration 60 , 61 . The second sample (PS-GaN) is a point-seed crystal grown via the Na-flux method and has ~ 10 20 cm −3 oxygen concentration 62 , 63 .…”

Demonstration of Observation of Dislocations in GaN by Novel Birefringence Method

“…Recently, the quality of free‐standing gallium nitride (GaN) substrates has been improved . For example, single‐crystal GaN substrates with a threading dislocation density (TDD) of 10 3 cm −2 are now available . There has also been progress in the methods of observing dislocations in GaN.…”

Hydride Vapor‐Phase Epitaxy Reactor for Bulk GaN Growth

“…The HVPE method allows to grow epitaxial layers of high purity and to produce uncompensated semi-insulating material [1]. The structural perfection of HVPE-grown layers is determined by the seed substrate quality: the dislocation density in the epitaxial layers grown on the bulk GaN substrate does not exceed the dislocation density in the substrate [2][3][4]. The HVPE method is also promising for the epitaxy of high-purity device structures [1].…”