Surface and Volume Decay Times of Photoconductivity in n-Type Silicon Wafers

Two photoconductive decay times in the surface and volume regions of silicon wafers can be separately derived from the microwave-detected photoconductive decay signals assuming two independent exponential functions for the annihilation of excess carriers. The surface decay times vary from 60 to 30 mu s when an n-type silicon wafer rinsed with a hydrofluoric acid solution is kept exposed to the air, while the volume decay times of around 2.5 mu s thus obtained are constant, as theoretically expected.