Abstract

MBE growth of GaAs is normally performed at a substrate temperature around 600 °C. It has recently become apparent, however, that GaAs grown at lower temperatures (LT GaAs) has some very interesting and useful properties. The material was first grown as a buffer layer to eliminate backgating in GaAs MESFET's, taking advantage of the high resistivity of this material [1]. Subsequently the LT GaAs was investigated as a photoconductive detector, where a response recovery of as short as 600 fs was observed [2]. The promise of this material for fast photoconductive devices has motivated a study of the carrier dynamics in LT GaAs. Gupta et al. [3] have investigated the time-resolved reflectivity of LT GaAs in an attempt to determine the carrier lifetime. Their sample was excited and probed high in the conduction band (at 620 nm), however, so interpretation of the results is not entirely straightforward. Therefore, we have performed transient absorption spectroscopy of the band-edge region of LT GaAs to directly determine the carrier dynamics.

© 1991 Optical Society of America