Turn on control of high power semiconductor devices by laser probing technique

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A Measuring system has been developed for measuring the excess carrier density in high-power devices by using a laser-probing technique. This system enabled us to obtain high-speed and precise special information about the carrier distribution during the turn-on stage and also to compare the experimental data with the simulation results. Following results are obtained.First, the required performance of the system was estimated for measuring the semiconductor device of several hundreds-μm thicknesses. By ray-tracing of the probe beam of l.55μm wavelength and using of fast response equipments, the time and special resolution of this system reached to 5.1ns and 35μm, respectively.In the second, the photo-excited carrier density formed in a silicon wafer irradiated by a YAG laser was shown to be 10^<18>cm^<-3> within 50ns. The PiN diode excited by pulsed voltage showed the concave shape of carrier density. These data were supported by the calculation results of 2D simulation code.In the third, the research of photo-triggered switch was advanced with the on state in irradiating PiN diode of the reversely biased condition with a pulse YAG laser light. The fast switching of 50ns was obtained at the reverse voltage of 35V and 6.0mJ output of YAG laser. The uniformly formed excess carrier of about 10^<18>cm^<-3> was observed.These obtained results of transient carrier distributions within a PiN diode that was excited optically or electrically showed the effectiveness of this evaluating and controlling system for high power devices in pulsed power operations.