Local oxidation of Ga[Al]As heterostructures with modulated tip-sample voltages

TL;DR

This study investigates local oxidation lithography on Ga[Al]As heterostructures using modulated tip-sample voltages, demonstrating improved oxide line quality and electronic device performance.

Contribution

It introduces voltage modulation during nanolithography, enhancing oxide aspect ratio, reliability, and reproducibility on GaAs-based heterostructures.

Findings

Enhanced oxide aspect ratio with voltage modulation

More reliable and reproducible oxidation process

Quantum devices show similar electronic properties with modulation

Abstract

Nanolithography based on local oxidation with a scanning force microscope has been performed on an undoped GaAs wafer and a Ga[Al]As heterostructure with an undoped GaAs cap layer and a shallow two-dimensional electron gas. The oxide growth and the resulting electronic properties of the patterned structures are compared for constant and modulated voltage applied to the conductive tip of the scanning force microscope. All the lithography has been performed in non-contact mode. Modulating the applied voltage enhances the aspect ratio of the oxide lines, which significantly strengthens the insulating properties of the lines on GaAs. In addition, the oxidation process is found to be more reliable and reproducible. Using this technique, a quantum point contact and a quantum wire have been defined and the electronic stability, the confinement potential and the electrical tunability are demonstrated to be similar to the oxidation with constant voltage.