The use of microwaves to characterize optically stimulated semiconductors

A theoretical model is developed describing the microwave transmission and reflection properties of semiconductor wafers after they have been illuminated with a short pulse of light from a laser. The absorption mechanism of the incident light pulse throughout the semiconductor is described giving the electron hole pair concentration as a function of position. The electron hole pair concentration during the decay process is also described as well as the microwave properties of the semiconductor as the electron hole pairs return to their equilibrium state. The theoretical model was tested experimentally using a 20 nano-second light pulse to illuminate a silicon wafer clamped between two flanges in a waveguide. The microwave energy transmitted through the wafer was measured with respect to time and the agreement with calculated values was found to be very good.