Optical Measurements of Surface Fields on Silicon Photoconductive Power Switches

We report further investigations of the surface electric fields present between the contacts of an optically controlled semiconductor switch. The experimental arrangement uses the Kerr electro-optic effect and a phase sensitive interferometric technique to measure the surface fields when a pulsed voltage is applied across a gap between two electrodes on planar samples fabricated on a silicon wafer. This technique allows us to measure the electric fields with a spatial resolution of about 50 microns and a temporal resolution of about 100 nanoseconds. This paper will discuss the experimental arrangement, present the recently obtained data and define further improvements in progress.