Abstract

Since the discovery of picosecond photoconductivity, optoelectronic switches made from a variety of materials have been studied [1]. A great number of applications have already been recognized and many new techniques depend on the availability of ultrafast (picosecond) devices. The two switches using composite electronic materials studied in this work are Fe-doped InGaAs grown on InP substrates and GaAs on a silicon-on-sapphire (SOS) substrate. The semi-insulating character of the Fe:InGaAs epilayer makes it very attractive for fabrication of integrated devices such as PIN photodetectors and FETs [2]. This material also exhibits a very high mobility (10000 cm²/Vs) and a photosensitivity extending up to 1.65 pm. The GaAs on SOS is of interest for the monolithic integration of GaAs and silicon devices where, for example, a GaAs FET could be integrated on a silicon wafer. This process takes advantage of the mature Si technology and the availability of low cost, high quality silicon wafers [3]. There is also interest for SOS as substrate because it provides better isolation and it is transparent. The interface silicon-sapphire exhibits a high density of defects, allowing faster devices to be fabricated. In our experiment, the sapphire substrate was used for mechanical strength. Whatever the material, the fabrication of a switch by deposition of metallic electrodes makes it possible to determine the switch characteristics and possible applications as well as to test the material optical properties.

© 1987 Optical Society of America