Growth of single crystal GaN substrate using hydride vapor phase epitaxy

Hydride vapor phase epitaxy (HVPE) was performed to prepare thick GaN films. It is found that (1) surface treatment of the sapphire substrate by the Ga+HCl gas just before the growth of GaN film reduces the pit density and improves the crystalline quality of the epitaxial GaN film, (2) the photoluminescence (PL) spectrum measured at 4.2 K shows the free A-exciton line and a narrow I2 line, indicating that the GaN crystals prepared in this study are of high purity and high crystalline quality, and (3) the magnitude of the strain of the homo-epitaxially grown GaN on a thick GaN buffer layer thus prepared is less than half that of a hetero-epitaxially grown GaN on sapphire. These results show that high quality, thick single crystals of GaN can be prepared homo-epitaxially using HVPE.