Performance of laser activated semiconductor opening switches

The authors report on the high-voltage operation of GaAs switches. The switches used were intrinsic GaAs and Cr:GaAs of bulk devices of millimeter sizes. The range of bias voltage applied was 500 V to 2 kV. The light source was a Q-switched Nd:YAG laser with 10-ns pulse duration. The closing and opening speeds of the Cr:GaAs switches were limited by the risetime and falltime of the laser pulse. Typical off-resistances when the laser light illumination was turned off were higher than 20 M Omega , whereas the on-resistances with laser illumination can be as low as 1 Omega . Such a large ratio of off-resistance to on-resistance allowed a switching efficiency of better than 99%. In the most practical inductive storage systems, the peak power transferred to the load is restricted by the switch opening time. The voltage multiplication can be achieved by the long duration of the current charging cycle, which in the case of the semiconductor switch is limited by the pulse duration of existing lasers. In order to remedy these two limitations, the authors are developing a laser system capable of delivering a laser pulse of several tens of nanoseconds and a very fast falltime.<>