Abstract

The most common approach to increasing the speed of photoconductive switches has been to reduce the carrier lifetime, either by bombardment with high-energy ions [1] or by the use of disordered materials [2]. In either case, the material defects, which act as centers for recombination, may also reduce the free-carrier mobility before recombination and thus unnecessarily lower the sensitivity of the photoconductor. An alternative approach to increasing the speed of response is to sweep the photoinduced carriers out of the gap with the applied voltage in a time short compared to their lifetime [3]. Here we describe the application of this technique to photoconductive switching in high mobility silicon. With sub-micron photoconductive gaps and carrier sweep-out the response time has been reduced from 700 psec to 27 psec. Electrical pulses of more than 1 volt have been switched with optical pulse energies of less than a nanojoule.

© 1985 Optical Society of America