Passivation effect of graphene on AlGaN/GaN Schottky diode

Abstract

Two dimensional graphene is a potential separation membrane and can improve interfacial conditions. In this paper, graphene was transferred to the surface of a AlGaN/GaN Schottky diode to investigate its influence on surface donor-like states (SDS) and Schottky barrier height. A fluorinated insulating monolayer of graphene transferred onto the AlGaN surface can suppress the surface leakage current by one order of magnitude at reverse and low forward bias. Meanwhile, a pristine monolayer of graphene under the gate metal can effectively reduce the gate current and shift the flat-band voltage positively by 0.45 V. Electrons from graphene can be trapped by SDS on the AlGaN surface and form a dipole layer. Some of the SDS become electrically neutral, and graphene as a separation membrane reduces SDS generated from AlGaN autoxidation. Therefore, two dimensional electronic gases (2DEG) can be depleted at higher gate bias, while the surface leakage path is cut off.