Growth of high crystalline quality semi-insulating GaN layers for high electron mobility transistor applications

Abstract

Semi-insulating character (sheet resistivity of 3.26×1011Ω∕sq) of thick GaN layers was developed for AlGaN∕GaN high electron mobility transistor (HEMT) applications on an AlN buffer layer. Electrical and structural properties were characterized by a dark current-voltage transmission line model, x-ray diffraction, and atomic force microscope measurements. The experimental results showed that compared to semi-insulating GaN grown on low temperature GaN nucleation, the crystal quality as well as surface morphology were remarkably improved. It was ascribed to the utilization of a high quality insulating AlN buffer layer and the GaN initial coalescence growth mode. Moreover, the significant increase of electron mobility in a HEMT structure suggests that this is a very promising method to obtain high performance AlGaN∕GaN HEMT structures on sapphire substrates.