Fabrication of quantum wires on GaAs substrates patterned by in situ electron-beam lithography

Abstract

In situ electron-beam (EB) lithography, a processing technique conducted entirely under an ultra-high vacuum environment, was used to pattern GaAs substrates on which quantum-wire structures were overgrown. First, a GaAs oxide-layer was selectively formed by EB-stimulated oxidation under a controlled oxygen atmosphere; it was then used as a mask material to define mesa stripes by Cl 2 gas-etching. Subsequently, ridge structures were formed on the mesa stripes by the overgrowth of a GaAs layer by molecular-beam epitaxy. Quantum-wire structures were fabricated on the top of the ridges by the growth of an AlGaAs GaAs quantum well. On the narrowest ridge structures, ∼20 nm wide quantum wires were successfully fabricated, as confirmed by cathodoluminescence measurements at 77 K.