A HIGHLY MISMATCHED INXGA1-XAS ALGAAS LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-0.5) PSEUDOMORPHIC HEMT ON GAAS SUBSTRATE USING AN INX/2GA1-X/2AS BUFFER LAYER/

A pseudomorphic HEMT with a large InAs mole fraction (x) for the chann el is fabricated successfully on a GaAs substrate by employing a thick Inx/2Ga1-x/2As buffer layer. The transconductance increases with incr easing InAs mole fraction, and shows a peak value at I = 0.4. The maxi mum transconductance and the cutoff frequency for a 1.7 mu m gate HEMT with x = 0.4 were 500 mS mm-l and 13.3 GHz, respectively. The effecti ve saturation velocity evaluated using the cutoff frequency increased with increasing x. (C) 1997 Elsevier Science Ltd.