PARALLEL CONDUCTION IN GAAS HETEROSTRUCTURES MODIFIED BY LOW-ENERGY ION EXPOSURE

We present a systematic study of the low-temperature magnetotransport properties of modulation-doped GaAs heterostructures co examine the de vice isolation mechanism in a low-energy (150 eV) Ar+ ion exposure pro cess. Measurements were carried out repeatedly on the same Hall bar as a function of the ion exposure time. A gradual evolution from paralle l conduction to strictly single-channel conduction was observed. The c arrier density of the upper channel was depleted by ion surface millin g, while the lower channel two-dimensional electron gas was essentiall y unaffected. The data indicated that carrier depletion and the subseq uent breakdown in electron screening of the long-range random potentia l was the main reason for device isolation during the low-energy ion e xposure process;in agreement with recent theoretical work. (C) 1996 Am erican Institute of Physics.