Structural properties of GaN epilayers directly grown on on-axis 6H-Si(0 0 0 1) by plasma-assisted MBE

摘要

We report on the structural properties of a series of thin GaN epilaryes directly grown on on-axis 6H-SiC(0 0 0 1) by plasma-assisted MBE. Xray measurements show that the crystlaline perfection of the laeyrs steadily improves with film thickness. In fact, the density of threading defects detected by transmission electron microscopy is found to decrease drastically with the distance away from the GaN/SiC interface, finally reaching a vlue of less thuan 5×10~9 cm~-2 at a layer thickness of 0.5 μm. The formation mechanisms of the threading dislocatoins in the GaN films are discussed in considration of the specific GaN/SiC interface structure.