Rapid Thermal Annealing for Surface Optimisation of ZnO Substrates for MBE-Grown Oxide Two-Dimensional Electron Gases

TL;DR

This paper presents a rapid thermal annealing and chemical etching process to improve ZnO substrate surface quality, enabling higher mobility 2DEGs for spintronics and quantum computing applications.

Contribution

It introduces a novel substrate treatment method combining thermal annealing and etching to enhance 2DEG growth quality on ZnO.

Findings

Achieved low-temperature mobility of 4.8×10^4 cm^2V^{-1}s^{-1} in 2DEGs

Annealed samples show at least three times lower scattering rate than unannealed controls

Surface treatment improves substrate quality for oxide 2DEG growth

Abstract

Two-dimensional electron gases (2DEGs) at the ZnO/ZnMgO interface are promising for applications in spintronics and quantum computing due to the combination of low spin-orbit coupling and high electron mobility. Growing high mobility 2DEGs requires high quality substrates with low impurity densities. In this work we demonstrate a ZnO substrate sample treatment combining high temperature rapid thermal annealing and chemical etching to improve the surface quality for the subsequent growth of 2DEGs. This process enables the growth of a 2DEG with low-temperature mobility of $4.8\times10^4$~cm$^2$V$^{-1}$s$^{-1}$. An unannealed control sample shows a scattering rate at least three times greater than the annealed sample.