Determination of surface state energy position of silicon in MOS structure using surface photovoltage (SPV) spectroscopy

Abstract

This paper dealt with the feasibility of Metal-OxideSemiconductor (MOS) structure as an alternative for Kelvin Probe Method. Specifically, this sought to monitor the band bending in the Gate-Oxide-Silicon interface and determine the surface state energy positions of Silicon in MOS using Surface Photovoltage (SPV) Spectroscopy. The spectral dependence on the Contact Potential Difference (CPD) of Silicon in MOS structure was mapped from 1998 nm to 400 nm emanated from the monochromator using Halogen as the light source. The CPD reading was proportional to the band bending within the surface space charge region that changed with photo-induced population and depopulation of surface states within the band gap. The sign of the slope of d(CPD)/d(hν) specified whether the conduction or the valence band was involved in the transition. Three states were found in the shallow state region with energy values near the band gap and one deep state found at 0.67 eV from sample 1. Results were comparable to the surface state energy position investigated using real silicon surface.