Comparison of minority-carrier diffusion length measurements in silicon by the photoconductive decay and surface photovoltage methods

Abstract

Diffusion lengths of minority carriers in the range 50–1200 μm were measured in n- and p-type silicon single crystals with a wide range of resistivities by the surface photovoltage (SPV) and photoconductive decay (PCD) methods. Previously published values for the optical absorption coefficient of Si differed sufficiently to result in a substantial uncertainty in the minority-carrier diffusion length determined by the SPV method. In order to minimize the uncertainty in diffusion length values obtained by the SPV method, the optical absorption coefficient of Si was measured in the wavelength interval 0.8≤λ≤1.16 μm [M. Saritas and H. D. McKell, J. Appl. Phys. 61, 4923 (1987)]. When our absorption coefficient data were used, the diffusion lengths measured by the SPV and PCD methods were found to be in agreement.