PRINCIPLE OF OPERATION AND CARRIER DISTRIBUTIONS OF ALGAAS/GAAS IN-PLANE-GATED CHANNELS

In-plane-gate field-effect transistors were fabricated on a modulation-doped AlGaAs/GaAs heterostructure substrate using focused ion beam implantation. The two-dimensional electron gas was divided up by insulating lines so as to define a coplanar gate and channel. The devices were simulated in two-dimensional cross section including the effects of fringing fields, surface states, and unintentional p-type doping in the nominally undoped GaAs buffer layer. Excellent agreement was obtained between measured and simulated channel conductance as a function of gate bias. The distribution of electrons in the channel was then studied as a function of gate bias. Simulations show that the two-dimensional electron gas in the channel is depleted through a combination of reduction in overall carrier density and effective width. The nonlateral depletion is enhanced by parasitic backgate coupling through the unintentionally doped buffer layer. © 1995 American Institute of Physics.