Improvement of Crystal Quality of RF-Plasma-Assisted Molecular Beam Epitaxy Grown Ga-Polarity GaN by High-Temperature Grown AlN Multiple Intermediate Layers

Abstract

The effects of high-temperature-grown AlN multiple intermediate layers (HT-AlN-MILs) on the crystal quality of Ga-polarity GaN layers grown on (0001) Al2O3 substrates by molecular beam epitaxy using rf-plasma nitrogen source were investigated. The high-temperature-grown AlN intermediate layers (HT-AlN-ILs) with different thicknesses were found to play different roles in the improvement of crystal quality. The 8-nm-thick HT-AlN-ILs brought about improvement of electrical properties. On the other hand, the 2-nm-thick HT-AlN-ILs improved the surface morphology. The combination of these 8-nm-HT-AlN-ILs and 2-nm-HT-AlN-ILs improved both the electrical properties and the surface morphology concurrently.