Need for Defects in Floating-Buffer AlGaN/GaN HEMTs

Carbon is a deep-level p-type acceptor in GaN and is used successfully in high-voltage AlGaN/GaN HEMT processes to generate a semi-insulating buffer for offstate leakage and breakdown suppression. However, ptype doping has also been linked to dynamic RON dispersion and current-collapse (CC) due to the absence of an Ohmic contact to the floating GaN buffer region. We demonstrate that current-collapse free C-doped HEMTs can be realized using epitaxial defects which short the floating buffer to the 2DEG.