Influence of layer structure and surface passivation on performance of AlGaN/GaN HEMTs on Si and SiC substrates

In this work, results of the comparative study of unpassivated and passivated AlGaN/GaN HEMTs which were grown on Si and SiC substrates and which consisted of intentionally undoped and doped layer structures. The doped structures consists of an undoped AlGaN spacer, Si-doped AlGaN carrier supply and an undoped AlGaN barrier layer. A100-150 nm thick SiO/sub 2/ and SiN are used as passivation layers. The induced charge, carrier density of used layer structures before and after passivation are studied. DC performance and small signal characterization of HEMT are also studied. It has been shown here that the AlGaN/GaN HEMT performance is improved and impact of passivation is less pronounced if a doped layer structure is used instead of undoped one.