Microwave Whispering-Gallery-Mode Photoconductivity Measurement of Recombination Lifetime in Silicon

We present a whispering-gallery-mode resonance-enhanced microwave-detected photoconductivity-decay method for contactless measurement of recombination lifetimes in high-resistivity semiconductor layers. We applied the method to undoped Si wafers of high resistivity, at 5 and 30 kOhm*cm, and measured conductivity relaxation times of 10 and 14 microseconds, respectively. In the wafers being considered, relaxation times are likely to be defined by the electron-hole diffusion from the bulk to the wafer surface.