Control of p-Type Conduction in a-Plane GaN Grown on Sapphire r-Plane Substrate

Mg-doped p-type a-plane GaN films were grown on high-quality unintentionally doped GaN on +0.5°-off r-plane sapphire substrates by metalorganic vapor phase epitaxy (MOVPE). A maximum hole concentration of 2.0×1018 cm-3 was reproducibly achieved at room temperature, which was higher than the maximum hole concentration of p-type c-plane GaN. The activation energy of Mg acceptors in p-type a-plane GaN with a hole concentration of 2.0×1018 cm-3 was found to be 118 meV by temperature-dependent Hall-effect measurement.