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 field-effect transistor (FET) structures by focused ion beam (FIB) implantation, 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 (>1015 cm−2) are introduced in the vicinity of a conductive channel at room temperature. The drain conductance Gd was studied in constricted channels with various nominal widths, W. It is found that Gd of a narrow channel (W∼1 μm) becomes quite small and nonlinear at low temperatures. When Gd is measured as a function of gate voltage, Vg, periodic oscillations are clearly observed at 15 K with a typical spacing of Vg∼60 mV, whereas the oscillation weakens and transforms to steplike structures at higher temperature (250 K). This oscillatory characteristic may possibly result from single electron transport through quantum dots associated with FIB-induced random potentials in the channel.