Quantum dots in Si/SiGe 2DEGs with Schottky top-gated leads

TL;DR

This paper demonstrates the fabrication and characterization of silicon/silicon-germanium quantum dots with Schottky top gates, enabling tunable tunnel barriers and Coulomb blockade effects in a 2DEG system.

Contribution

First implementation of Schottky top gates for quantum dots in Si/SiGe 2DEGs, reducing leakage and enabling gate-controlled tunneling.

Findings

Successful fabrication of quantum dots with Schottky top gates

Observation of Coulomb blockade oscillations

Reduced gate leakage through design optimizations

Abstract

We report on the fabrication and characterization of quantum dot devices in a Schottky-gated silicon/silicon-germanium two-dimensional electron gas (2DEG). The dots are confined laterally inside an etch-defined channel, while their potential is modulated by an etch-defined 2DEG gate in the plane of the dot. For the first time in this material, Schottky top gates are used to define and tune the tunnel barriers of the dot. The leakage current from the gates is reduced by minimizing their active area. Further suppression of the leakage is achieved by increasing the etch depth of the channel. The top gates are used to put the dot into the Coulomb blockade regime, and conductance oscillations are observed as the voltage on the side gate is varied.