Structural Control of Cubic and Hexagonal GaN by Changing the Electric Bias during ECR-MBE Growth

Abstract

Controlling the crystal structure of GaN as either cubic (c-) or hexagonal (h-) GaN by changing the electric bias during growth was studied. After growth, we used transmission electron microscopy (TEM) and X-ray diffraction to determine the microstructure of c-GaN and h-GaN. Although c-GaN was confirmed, the interface at h-GaN/c-GaN was not clear. To increase the transition rates of crystal structure at the interface, we added hydrogen as a hydrogen–nitrogen mixed gas plasma while changing the electric bias. When we introduced hydrogen for 20 s while simultaneously changing the electric bias from 20 to 0 V, the crystal structure of GaN changed abruptly from cubic to hexagonal. TEM observations showed that the interface contained a thin layer with a high density of stacking faults, indicating that addition of hydrogen clearly assisted the change of crystal structure by forming stacking faults.