Effect of Thermal Annealing on the GaN Metal-Oxide-Semiconductor Capacitors with Gallium Oxide Gate Layer

In this study, gallium nitride (GaN)-based metal-oxide-semiconductor diodes with a gallium oxide gate layer formed by ac bias-assisted photoelectrochemical oxidation of n-type GaN in were demonstrated. A typical flatband voltage of 4.35 V was obtained by capacitance–voltage measurement. The observed curves shifted toward the negative voltage side when the heterostructures were annealed in ambient oxygen . This result could be tentatively attributed to the fact that the negative effective charges existing in the layer and/or in the interface could be reduced due to the ambient annealing process. A negative value of the effective charge density of , which corresponds to an effective insulator charge number density of around , was obtained.