Epitaxial Growth of Undoped and Mg-Doped GaN

Gallium nitride was epitaxially grown on {0001} and {102} sapphire by the vapor phase reaction of Ga-HCl-NH3-Ar system. The growth rate on {102} sapphire is ~12 µm/hr, which is higher than that on {0001} sapphire by a factor of ~1.5. The crystal on {1102} sapphire has a lower carrier concentration than that of the same thickness on {0001} sapphire by a factor of ~0.5. The lowest carrier concentration and the highest electron mobility of undoped GaN obtained in this study were 1.6×1019 cm-3 and 78 cm2/Vs, respectively, at 300 K. When heavily doped with Mg, the crystal grown changes markedly in growth morphology. The orientation relationships developed in an undoped or lightly Mg-doped state are {0001}GaN//{0001}sapphire and {110}GaN//{102}sapphire, and in a heavily doped state {114}GaN//{0001}sapphire and {110}GaN//{102}sapphire.