Total photoelectron yield spectroscopy of energy distribution of electronic states density at GaN surface and SiO ₂ /GaN interface

Abstract

Abstract The energy distribution of the electronic state density of wet-cleaned epitaxial GaN surfaces and SiO 2 /GaN structures has been studied by total photoelectron yield spectroscopy (PYS). By X-ray photoelectron spectroscopy (XPS) analysis, the energy band diagram for a wet-cleaned epitaxial GaN surface such as the energy level of the valence band top and electron affinity has been determined to obtain a better understanding of the measured PYS signals. The electronic state density of GaN surface with different carrier concentrations in the energy region corresponding to the GaN bandgap has been evaluated. Also, the interface defect state density of SiO 2 /GaN structures was also estimated by not only PYS analysis but also capacitance–voltage ( C – V ) characteristics. We have demonstrated that PYS analysis enables the evaluation of defect state density filled with electrons at the SiO 2 /GaN interface in the energy region corresponding to the GaN midgap, which is difficult to estimate by C – V measurement of MOS capacitors.