Extrinsic Surface Photovoltage Spectroscopy — An Alternative Approach To Deep Level Characterisation In Semiconductors

Abstract

Surface photovoltage (SPV) spectroscopy in the intrinsic absorption energy range has been successfully used to study semiconductor surface and interface states [1, 2, 3, 4, 5, 6]. However, simultaneously with the surface states, deep levels in the semiconductor bulk can also be optically excited, thus changing the surface potential [6]. This makes feasible the use of extrinsic SPV spectroscopy for the assessment of deep bulk semiconductor levels, which are a subject of increasing interest from both a fundamental and a technological viewpoint. At the same time, a further improvement of the SPV spectra analyses is necessary, in order to take into account the contributions to the surface potential of both surface and bulk electron transitions stimulated by extrinsic illumination. Theoretical and experimental studies supporting the concept depicted above have been already performed [1,2]. The comparison of the extrinsic SPV and photoconductivity (PC) spectra is of prime interest in studying the validity and the applicability of this concept.