Interpretation of microwave-detected photoconductance decay lifetime measurements

The microwave-detected photoconductance decay technique is potentially useful for its ability to make rapid, contactless measurements of carrier lifetimes. However, there are questions as to the effects of nonuniform excitation of the sample and resultant two-dimensional carrier distributions on the measured microwave reflectance transients, and therefore, the deduced carrier lifetimes. Also, it is not possible to nondestructively distinguish between bulk and surface recombination at the present. The reflectance behavior of a few relevant carrier distributions is investigated. Results demonstrate that the measured reflectance has negligible dependence on the distribution of carriers normal to the sample surfaces, but may significantly depend upon carrier distributions parallel to the sample surfaces