FORMATION OF GAAS ALGAAS CONSTRICTED-CHANNEL FIELD-EFFECT TRANSISTOR STRUCTURES BY FOCUSED GA IMPLANTATION AND TRANSPORT OF ELECTRONS VIA FOCUSED ION-BEAM-INDUCED LOCALIZED STATES/

We report on the fabrication of n-AlGaAs/GaAs constricted-channel fiel d-effect transistor (FET) structures by focused ion beam (FIB) implant ation, and study transport properties of low-dimensional electrons via FIB induced localized states. In this work, quantum wire FET samples with in-plane gates and top gate were formed by using a focused Ga ion beam by which Ga ions of a high dose density (>10(15) cm(-2)) are int roduced in the vicinity of a conductive channel at room temperature. T he drain conductance G(d) was studied in constricted channels with var ious nominal widths, W. It is found that G(d) Of a narrow channel (W-l mu m) becomes quite small and nonlinear at low temperatures. When G(d ) is measured as a function of gate voltage, V-g, periodic oscillation s are clearly observed at 15 K with a typical spacing of V-g similar t o 60 mV, whereas the oscillation weakens and transforms to steplike st ructures at higher temperature (250 K). This oscillatory characteristi c may possibly result from single electron transport through quantum d ots associated with FIB-induced random potentials in the channel. (C) 1998 American Vacuum Society.