SHIFT IN THRESHOLD VOLTAGE AND SCHOTTKY-BARRIER HEIGHT OF MOLYBDENUM GATE GALLIUM-ARSENIDE FIELD-EFFECT TRANSISTORS AFTER HIGH FORWARD GATECURRENT TEST

The threshold voltage and the Schottky barrier height of InGaAs/AlGaAs HEMTs or GaAs MESFETs with molybdenum Schottky gates were observed to shift after high forward gate current tests, and the shift was recove red by subsequent heat treatment. Experimental results show that this phenomenon is characteristic of molybdenum Schottky gates on GaAs, and it is related to the deep traps near the interface between molybdenum and GaAs or within the GaAs channel layer. Such deep traps were intro duced due to the electron irradiation effect during the electron beam deposition of the molybdenum (Mo) on GaAs. Insertion of a thin Ti laye r between Mo and GaAs was found to be effective for suppressing the sh ift.