Vapor phase epitaxy of GaN using GaCl₃/N₂ and NH₃/N₂

Thermodynamic calculations were done on chloride transport vapor phase epitaxy of GaN using GaCl₃/N₂ and NH₃/N₂. At typical growth temperature and gas flow rates, both GaN formation and gas phase etching reactions of GaN were thermodynamically favored. Under thermodynamic equilibrium, most ammonia should decompose to nitrogen and hydrogen gases and gas phase etching of GaN occurs by HCl. From experimental measurements, less than 10% of the incoming ammonia decomposes and under this condition, GaN formation from GaCl₃/N₂ and NH₃/N₂ is thermodynamically favored. This calculation matches our experimental results. Experimentally, we have optimized the growth conditions of GaN. High crystalline quality thick GaN films (10-15 μm) were grown on c-Al₂O₃. The GaN films show band-edge emission dominated PL at both room temperature and 77 K. From the φ-scan: the GaN films grown on c-Al₂O₃ are single crystalline. The typical growth rates were about 10-15 μm/h.