HIGH-PERFORMANCE HETEROSTRUCTURE FIELD-EFFECT TRANSISTORS (HFETS) WITH STEP-MODULATIONED INGAAS CHANNEL STRUCTURE

Two types of new heterostructure field-effect transistors are fabricat ed and investigated in this paper. The pseudomorphic InxGa1-xAs (x les s than or equal to 0.2) and Al(0.3)G(0.7)As (or In(0.49)G(0.51)P) laye rs are used as the active channel and Schottky contact layer, respecti vely, in these studied devices. Owing to the large conduction band dis continuity (Delta E-C) at InxGa1-xAs/Al0.3Ga0.7As and InxGa1-xAs/In0.4 9Ga0.51P interfaces, the carriers can be easily confined in the channe ls. Thus the device characteristics such as drain saturation current, breakdown voltage and transconductance (g(m)) are improved. Furthermor e, by varying the doping concentration or In composition in the channe l, both the high carrier density and high output current may be obtain ed as a result of the significant carrier accumulation effect. From th e experimental results, these studied devices show their great potenti al in high-power and high-speed circuit applications. (C) 1998 Elsevie r Science S.A.