Depletion mode modulation doped Al0.48In0.52As-Ga0.47In0.53As heterojunction field effect transistors

We report the first demonstration of a depletion mode modulation doped Ga0.47In0.53As field effect transistor. This transistor combines the advantage of modulation doping and the superior material characteristics of Ga0.47In0.53As. DC transconductances of 31 mmho/ mm at 300 K and 69 mmho/mm at 77 K have been measured for a device with 5.2µm gate length and 340 µm gate width. An enhanced drift mobility is responsible for 88 percent of the improvement in the transconductance at 77 K and the remaining 12 percent is attributed to an improved ohmic contact. A high performance modulation doped Ga0.47In0.53As FET is expected to play an important role in very high speed digital and analog applications.