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.