Measurement of Minority Carrier Lifetimes with the Surface Photovoltage

Abstract

The surface photovoltage method uses the junction-like properties of a semiconductor surface as a means for studying the decay of excess carriers. No more than capacitive contact with the specimen is required to detect the surface photovoltage which, in the millivolt range, is a linear function of the excess carrier density. Theoretically, the surface method yields exactly the same carrier decay constant as the photoconductivity method when the lowest diffusion mode prevails in the specimen. This has been quantitatively confirmed for Ge: only qualitative confirmation has been made with Si. For surfaces tending toward inversion, the surface method gives larger signals than the photoconductivity method, particularly for semiconductors with low intrinsic carrier density. On the other hand, for accumulation layer surfaces the surface method usually gives smaller output signals.