Application of high-frequency contactless method of PEM investigations to examine near-surface layer of Si and GaAs

The recently reported contactless photoelectromagnetic (PEM) method of determining carrier lifetimes was used to investigate Ga:AS:Te and Si:B samples with polished and grinded surfaces. In the presented experiments the samples were illuminated with radiation of different wavelengths (and different absorption coefficients) emitted by diode lasers, argon and HeNe lasers acoustooptically modulated up to 100 kHz. The frequency dependence of PEM magnetic flux registered for cases of excess carriers photogeneration at different depths in a sample are presented and fitted with theoretical dependencies. It allows an evaluation of the bulk and near-surface region electron and hole lifetimes.