Oxide Dielectrics for Reliable Passivation of AlGaN/GaN HEMTs and Insulated Gates

Dielectric oxides of scandium and magnesium have been employed as a surface passivation on AlGaN/GaN HEMT devices. Research to discover a lower lattice mismatch oxide to further reduce the interface trap density and increase oxide/nitride stability has lead to adding calcium to the MgO to create a crystalline film of MgCaO that is a closer lattice match to GaN. Stability of the dielectric films was determined for environmental and thermal processes and a 5nm cap of Sc2O3 was found to increase the stability of the MgCaO over that of the MgO. Passivation effects of the oxide dielectrics maintained pulse currents that were twice that of SiNx passivation after 5 weeks of aging at 200{degree sign}C. A newer capping material of (Sc2O3)x(Ga2O3) 1-x has been developed that provides for double the breakdown field of the previous Sc2O3 capping layer.