The Electrical and Optical Properties of GaAs with as Precipitates (GaAs:As)

Since its initial report by the IBM/Purdue University group in 1990, GaAs with As precipitates (GaAs:As) has been shown by this group to exhibit unusual and useful electrical and optical properties. In this paper we review our progress in understanding the fundamental properties of this material. We have shown that both the electrical and optical properties of GaAs:As arc explained by assuming that the GaAs is of good crystalline quality and that the As precipitates act as buried Schottky barriers. This model accounts for its semi-insulating stability against both n- and p-type doping, its high-speed photoconductive behavior, and its ability to detect 1.3 micron light when it forms the “I” layer of a PIN photodiode via the internal photoemission process. Using modulation spectroscopy we clarify the fundamental differences between GaAs:As and unannealed GaAs grown at 200 C. We also show that GaAs:As used as a 1.3 micron detector in the metal-semiconductor-metal device structure format, has a photoconductive bandwidth in excess of 50 GHz.