Characteristics of nonalloyed pseudomorphic high electron mobility transistors using InAs/InxGa1-xAs (x=→0) AlyGa1-yAs (y=0→0.3) contact structures

A molecular beam epitaxy InAs/InxGa1-xAs (x = 1 --> 0)/AlyGa1-yAs (y = 0 --> 0.3) heterojunction was used as an ohmic contact structure to the GaAs-based pseudomorphic high electron mobility transistors (PHEMTs). This nonalloyed PHEMT had a specific contact resistance r(c) of 1.05 x 10(-7) Omega . cm(2) and an extrinsic transconductance g(me) of 272 mS/mm for devices with 1 mu m gate-length, microwave measurements shelved a current gain cut-off frequency f(t) of 22 GHz and a maximum oscillation frequency f(max) of 43 GHz. These results are comparable to our best conventional PHEMTs' alloyed at 450 degrees C and 2 min duration. Meanwhile, a small-signal equivalent circuit model of the nonalloyed PHEMT has also been demonstrated.