In/sub 0.52/Al/sub 0.48/As/InAs/InxAl/sub 1-x/As pseudomorphic HEMT's on InP

The DC and microwave performance of an InAs channel HEMT is reported. Room-temperature electron mobility as high as 20200 cm
²
/Vs is measured, with a high carrier concentration of 2.7×10/sup 12/ cm/sup -2/. DC extrinsic transconductance of 714 mS/mm is measured and a unity-current-gain cut-off frequency of 50 GHz is obtained for a 1.1-μm gate length HEMT. The success of achieving superior Hall mobility and device performance is strongly dependent on the In/sub x/Al/sub 1-x/As buffer layer design that changes the lattice constant from lattice-matched In/sub 0.52/Al/sub 0.48/As to In/sub 0.75/Al/sub 0.25/As. The multiple In/sub 0.52/Al/sub 0.48/As/InAs monolayer superlattices buffer achieves the best performance as compared to the step-graded In/sub x/Al/sub 1-x/As and the uniform In/sub 0.76/Al/sub 0.25/As buffer.