STRUCTURAL DEPENDENCE OF GAN AL2O3 ON ELECTRIC BIAS DURING ELECTRON-CYCLOTRON-RESONANCE PLASMA-EXCITED MOLECULAR-BEAM EPITAXY (ECR-MBE)/

GaN crystals were grown on a (0001) sapphire substrate by electron cyc lotron resonance plasma excited molecular beam epitaxy (ECR-MBE). Grow n crystals were analyzed by photoluminescence (PL) measurement at low temperatures and by pole figure mode X-ray diffraction (XRD) mapping. The GaN crystal structure changed from hexagonal dominant to cubic dom inant as the V/III ratio decreased. It was also observed for the first time that a similar structural change occurred upon the application o f a bias voltage to the substrate. This structural change was consider ed to be induced by the change in the effective V/III ratio on the gro wing surface introduced by the positive bias. These results imply the possibility of growing hexagonal and cubic heterostructures and supper lattices by simply changing the bias voltage during growth.