Analysis of charge control in pseudomorphic two-dimensional electron gas field-effect transistors

An exact model for charge control in two-dimensional field-effect transistors (2DEGFETs) is discussed. The model is based on a first-principles theory, in which self-consistent quantum two-dimensional electron subbands and numerical solutions of Poisson´s equation for band bending, space charge, and three-dimensional holes are included. The charge control in InGaAs/AlGaAs pseudomorphic 2DEGFETs is analyzed and compared with that in the GaAs/AlGaAs conventional 2DEGFET. It is shown that a quantum-well channel in the pseudomorphic 2DEGFET can achieve high carrier confinement as well as high carrier concentration. From the calculated gate capacitance-voltage behavior, a simple estimation for the device performance is obtained. The results indicate that the pseudomorphic 2DEGFET with a large conduction band discontinuity at the channel interface can improve transconductance-gate voltage characteristics, and thus maximum transconductance, and the cutoff frequency-gate voltage characteristics