Determination of Bulk Diffusion Lengths for Angle-Lapped Semiconductor Material Via the Scanning Electron Microscope: A Theoretical Analysis

摘要

A standard procedure for the determintion of the minority carrier diffusion length by means of a scanning electron microscope (SEM) consists in scanning across an angle-lapped surface of a P--N junction and measuring the resultant short circuit current I/sub sc/ as a function of beam position. A detailed analysis of the I/sub sc/ originating from this configuration is presented. It is found that, for a point source excitation, the I/sub sc/ depends very simply on x, the variable distance between the surface and the junction edge. The expression for the I/sub sc/ of a planar junction device is well known. If d, the constant distance between the plane of the surface of the semiconductor and the junction edge in the expression for the I/sub sc/ of a planar junction is merely replaced by x, the variable distance of the corresponding angle-lapped junction, an expression results which is correct to within a small fraction of a percent as long as the angle between the surfaces, 2 theta sub 1 , is amaller than 10 exp 0 . (ERA citation 04:029596)