Surface Passivation of AlGaN terminated and GaN Terminated HEMT Structures Studied by XPS

Abstract

ABSTRACTSamples of both AlGaN and GaN terminated HEMT structures were studied using x-ray photo spectroscopy (XPS). It was found that the XPS spectra of both AlGaN and native oxide surfaces were shifted by a surface charge of 0.5 to 1.0 eV. The samples were then oxidized using an UV-ozone treatment for 25 minutes at room temperature. The ozone oxide XPS spectra of the AlGaN terminated surface was found to have the same 0.5 to 1.0 eV shift while the ozone oxide XPS spectra of the GaN terminated surface was found to have a 5.0 eV shift, indicating that the native GaN oxide is more insulating. Processed HEMT devices using both surface terminations were given the same UV-ozone treatment followed by a 10nm MBE grown Sc2O3 film for passivation. The GaN terminated HEMT structures showed on average a 10% increase in channel current (from gate-lag measurements, pulse mode) over the AlGaN terminated HEMT structures.