Abstract

Gallium arsenide grown by molecular beam epitaxy at low substrate temperatures (LT-GaAs)¹ has recently become recognized for its unique and useful opto-electronic properties. As-grown samples prepared in the temperature range 180-250°C contain numerous defects and are characterized by short carrier lifetime² and low resistivity and mobility. When annealed, arsenic precipitates form in the films, which still maintain their short carrier lifetime, but also exhibit an enhanced dark resistivity³ and a high mobility. Therefore, while numerous applications using these annealed films have been demonstrated, uses for unannealed LT-GaAs have essentially been ignored. Here we demonstrate, for the first time, photoconductive switching and subpicosecond electrical pulse generation using as-grown LT-GaAs cooled to low temperatures. In addition, through femtosecond transient reflectivity, we have studied the temperature-dependent temporal response of the carrier behavior of the thick layers of both annealed and unannealed material used in the switching investigation.

© 1993 Optical Society of America