The Effect of Defects with Deep Levels on the C–V Characteristics of High-Power AlGaN/GaN/SiC HEMTs

— This study deals with the capacity–voltage ( С–V ) characteristics of the gate–drain regions of crystals of high-power microwave HEMT transistors with a large gate periphery of the S and Х bands and a source–drain breakdown voltage V DS ranging from 30 to 150 V, as well as test Schottky diodes formed in a single technological cycle together with HEMTs. Capacitance deep-level transient spectroscopy (DLTS) was used to investigate the structural defects creating deep levels. During the investigations, it was shown that the С–V curves of HEMT crystals always had two areas of change in capacitance with differing slope angles, while there were no such knees in the curves for the test Schottky barriers (SBs). The DLTS technique revealed that НЕМТs and test SBs contained electron-like and hole-like traps, occurring, most probably, in the buffer layer, and also a hole-type peak behaving anomalously. The knee in the С–V curves of НЕМТs is due to the strong electric fields arising at the edge of the gate of the transistor structures.