Backgating in pseudomorphic In/sub 0.15/Ga/sub 0.85/As/Al/sub 0.25/Ga/sub 0.75/As MODFET's with a GaAs:Er buffer layer

A new GaAs:Er buffer layer grown by MBE has been developed which significantly reduces backgating currents (by 3 to 4 orders of magnitude) in pseudomorphic InGaAs/AlGaAs modulation-doped field effect transistors (MODFET's). The buffer layer is highly resistive, in the 10/sup 2/-10/sup 5/ /spl Omega//spl middot/cm range over the Er-doping range investigated. Presence of internal Schottky barriers resulting from high-density ErAs precipitates has been proposed to he the cause of the high resistivity.