Minority Carrier Diffusion Lengths in Silicon Slices and Shallow Junction Devices

Abstract

Measurements of surface photovoltage as a function of the wavelength of incident light provide a convenient method for the determination of minority carrier diffusion length in semiconductors. The diffusion length in silicon slices with a thickness greater than twice the diffusion length has been measured by the steady-state surface photovoltage method with a single laboratory reproducibility of ± 10% over a long period of time. Radial variations in diffusion length in silicon slices as well as the effects of heat treatment have been studied. The diffusion length in the base region of shallow junction devices has been measured by the collection of short-circuit current as a function of the wavelength of incident light. The single laboratory reproducibility of this method for the determination of diffusion length in single crystalline and polycrystalline silicon solar cells is also about ± 10%.