Two-step growth of high-quality GaN by hydride vapor-phase epitaxy

The use of a low-temperature layer of GaN formed by hydride vapor-phase epitaxy (HVPE) as a template to grow high-quality HVPE films is demonstrated. Using layers formed by reacting GaCl and ${\mathrm{NH}}_{\mathrm{3}}$ at $\text{550\hspace{0.05em}°}\mathrm{C}$ and annealed at a growth temperature of $\text{1050\hspace{0.05em}°}\mathrm{C},$ thick films of GaN can be grown by HVPE with fewer than ${10}^8$ dislocations per ${\mathrm{cm}}^{\mathrm{2}}.$ Dislocation densities measured by high-resolution x-ray diffraction, atomic-force microscopy step termination density and plan-view transmission electron miscroscopy reveal that $\text{∼23\hspace{0.05em}μ}\mathrm{m}$ films have dislocation densities of ${\text{∼6×10}}^7 {\mathrm{cm}}^{\mathrm{-2}}.$ Obtaining high-quality single-crystal character films was found to be dependent on several factors, most importantly, the rate of temperature increase to growth temperature and the layer thickness.