TRANSPORT OF QUASI-2-DIMENSIONAL ELECTRONS IN HETEROJUNCTION FIELD-EFFECT TRANSISTORS

High and low field transport properties of electrons confined to quasi-two-dimensional sheets in semiconductor heterostructures are discussed within the context of their importance in the operation of field effect transistors. Modulation-doped heterostructures, in which the two-dimensional electron gas is in undoped material, have extremely large mobilities; these mobilities are larger than what can actually be fully used by the transistor. Doped-channel quantum well structures have lower mobilities and velocities, but field effect transistors fabricated from such structures operate very well in part because of the larger electron concentration which is possible.