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

Semi-insulating character ( sheet resistivity of 3.26 x 10(11) ohm/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. (c) 2006 American Institute of Physics.