Range of validity of the surface-photovoltage diffusion length measurement: A computer simulation

Abstract

The surface-photovoltage diffusion length measurement is analyzed in depth to determine its range of applicability and cause of failure when it no longer yields the diffusion length. It is shown that this technique is generally not valid for amorphous materials, but is highly useful for crystalline semiconductors. The problem of applicability of the surface-photovoltage diffusion length measurement to amorphous materials is not alleviated by using thicker samples or by using chopped light illumination through the back. It is determined that the validity of the surface-photovoltage method requires a density of midgap states <1013 cm−3 eV−1.