Low temperature grown GaAs materials and devices: present status and trends

GaAs layers can be grown epitaxially over a wide range of temperature reaching from 180/spl deg/C up to the thermal stability limit. While above 400/spl deg/C growth temperature the stoichiometry is preserved within the ppm-range, at low growth temperature surplus As can be incorporated into the GaAs matrix within the percentage range. The material grown in this lower temperature range is called Low-Temperature-Grown (LTG) GaAs. By high temperature annealing the solubility limit will be surpassed and most of the excess As precipitates. Thus, the material can have a variety of unusual properties. The first application was in the FET buffer layer structure virtually eliminating backgating and short channel effects. Using LTG-GaAs, the stability of GaAs FET devices has been improved dramatically and the Schottky gate breakdown limit has been surpassed for the first time. The second successful application is ultrafast THz optoelectronic switches and detectors. In this paper the advances in FET's are reviewed.