Microstructural properties and atomic arrangements in GaN/sapphire and AlxGa1−xN∕AlN∕GaN∕sapphire heterostructures

Abstract

Microstructural and atomic structure studies of GaN/sapphire and AlxGa1−xN∕AlN∕GaN heterointerfaces have been performed by using bright-field transmission electron microscopy (TEM) and selected area electron diffraction pattern (SADP) measurements. TEM and SADP results from the GaN/sapphire and the Al0.4Ga0.6N∕AlN∕GaN∕sapphire heterointerfaces showed that GaN epilayers and Al0.4Ga0.6N, AlN, and GaN active layers, respectively, had been grown on the sapphire substrates. The values of the strain and the stress in the Al0.4Ga0.6N, the AlN, and the GaN layers were determined. Possible schematic diagrams of the two heterostructures, as well as diagrams of the [21¯1¯0] projections of the GaN epilayer and the Al0.4Ga0.6N∕AlN∕GaN heterostructure, are presented based on the TEM and SADP results. These results can help improve the understanding of the microstructural properties of the strained AlxGa1−xN∕AlN∕GaN∕sapphire heterostructures for applications in the high-speed and high-power electronic devices.