INFLUENCE OF AN INHOMOGENEOUS SPATIAL-DISTRIBUTION OF DEFECTS ON THE CONSTANT PHOTOCURRENT METHOD

The constant photocurrent method has been widely used in hydrogenated amorphous silicon as an efficient way of determining the optical absor ption coefficient in the low-absorption region, and of estimating the defect density in the band gap. However, while the analysis is general ly carried out on the assumption of uniform material parameters throug hout the sample the experimental situation may fail to approximate tha t model. We therefore examine the influence on the resolved defect den sity of an inhomogeneous spatial distribution of defects, and of surfa ce recombination, by means of a steady-state diffusion equation for ph otoexcited carriers. Differences by as much as a factor of 2 are obser ved within the range of possible experimental circumstances. (C) 1997 American Institute of Physics.