Epitaxial Growth of Undoped and Mg-Doped GaN

Gallium nitride was epitaxially grown on {0001} and {1 02} sapphire by the vapor phase reaction of Ga-HCl-NH 3 -Ar system. The growth rate on {1 02} 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 1.6×10 19 cm -3 and 78 cm 2 /V·s, 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 {11 0} GaN //{1 02} sapphire , and in a heavily doped state {11 4} GaN //{0001} sapphire and {11 0} GaN //{1 02} sapphire .