ALL-REFRACTORY GAAS-FET USING AMORPHOUS TIWSIX SOURCE DRAIN METALLIZATION AND GRADED-INXGA1-XAS LAYERS

We report on the fabrication of an all-refractory GaAs field-effect tr ansistor having non-alloyed source and drain ohmic contacts and a TiW/ Au refractory gate metallization. The ohmic contacts consist of amorph ous TiWSi(x) metallization and intervening graded InGaAs layers grown by low pressure organometallic vapor phase epitaxy (LPOMVPE). The amor phous TiWSi(x) is formed using alternating layers of TiW(10 angstrom) and Si(1.5 angstrom) deposited by an RF magnetron sputtering technique . The resulting all-refractory FET devices exhibited excellent dc tran sistor characteristics with measured transconductance of 140 mS/mm. Th e dc performance of these devices was comparable to conventional devic es with AuGe/Ni/Au contacts fabricated using similar material structur es.