A new spectroscopic method for determination of energy distribution of interface states in the semiconductor band-gap

Abstract

Measurements of X-ray photoelectron spectra (XPS) are performed for (3 nm-Pt/2.6 nm-oxide/p-InP(100)) and (2.5 nm-Pt/3.8 nm-oxide/n-GaAs(100)) MOS devices under biases. Upon applying a negative bias voltage to the InP (or GaAs) substrate with respect to the Pt layer, the substrate In 3d 5 2 (or As 3d 5 2 ) peak is shifted toward the lower binding energy, while it is shifted toward the higher binding energy by applying a positive bias. These shifts are caused by a change in the potential drop across the oxide layer due to accumulation of charges in interface states. The energy distribution of the interface states in the band-gap is obtained by analyzing the magnitudes of these shifts measured as a function of the bias voltage. The energy distribution has peaked-structure and the peaks are attributed to antisite and vacancy defects. The interface Fermi level of InP (or GaAs) is located near the energy level of the (+/0) transition of the P In (or As Ga) antisite defects.