Quantum device microfabrication: Resolution limits of ion beam patterning

We have achieved precise control of the lateral electrical damage accompanying ion beam patterning of submicron electron devices from semiconductor materials. In situ transport measurements, made in the etching chamber during the definition process, provide an exact and reproducible means of end-point detection, irrespective of material structure and ion beam parameters. We apply this to routinely fabricate conducting channels having widths below 100 nm from high-mobility GaAs/AlGaAs heterojunctions. Subsequent low-temperature magnetotransport measurements and successive optimization of processing conditions enable us to systematically obtain the minimum conducting width. Through these studies we explore the ultimate resolution limits of the ion beam patterning process.