Vapor phase epitaxy of GaN using GaCl3/N-2 and NH3/N-2

Thermodynamic calculations were done on chloride transport vapor phase epitaxy of GaN using GaCl3/N-2 and NH3/N-2. 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/N-2 and NH3/N-2 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 mu m) were grown on c-Al2O3. The GaN films show band-edge emission dominated PL at both room temperature and 77 K. From the phi-scan, the GaN films grown on c-Al2O3 are single crystalline. The typical growth rates were about 10-15 mu m/h.