Microwave-detected photoconductance decay

Abstract

Microwave-detected photoconductance decay provides a contactless measurement of the recombination lifetime of free carriers in semiconductors following a pulse of optical excitation. Several complications in interpreting the results obtained by this method have prevented its widespread acceptance. Detailed models are proposed and verified experimentally using a commercially available apparatus. The model adequately predicts the behavior of the microwave reflectance as a function of wafer conductivity and system configuration. A light-biased variation of the technique which makes it possible to characterize lifetimes as a function of excess carrier density is described. This capability makes it possible to measure the emitter saturation current density for diffusion in high-resistivity wafers, a valuable process control tool.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>