Interface charge engineering in GaN-based MIS-HEMTs

Atomic layer deposited Al2O3/III-nitride interfacial charge properties were investigated experimentally. Substantial amount of positive interface fixed charges (> 1.8×1013 cm-2) were observed on all the orientations of GaN and Ga-polar AlGaN. These interface charges bring large impact on electron transport especially in vertically scaled devices. Post-metallization anneals is one of the methods which can significantly alter this sheet charge in the case of Al2O3 on GaN. Oxygen plasma is another approach to efficiently reduce the interface charges at Al2O3/AlGaN. The interface charge density engineering described here can be used to improve performance of device such as gate leakage and electron transport, and also provides a new design of normally-off MISHEMTs.