Current instabilities in GaN-based devices

Current dispersion effects have been experimentally investigated in a variety of AlGaN/GaN heterostructure FETs with large signal and switching measurements including HEMTs with doped and undoped barrier layer. A range of dispersion frequencies from 10/sup -3/ Hz to 10 GHz were observed, where the output current amplitude is drastically reduced. Through this effect the full channel charge of an AlGaN/GaN heterostructure FET may be completely depleted under specific bias conditions. This indicates that this phenomena cannot be related to deep traps alone, but is also connected to piezorelated charge states and conduction to these states.