Wafer-scale low-disorder 2DEG in $^{28}$Si/SiGe without an epitaxial Si cap

TL;DR

This paper demonstrates a wafer-scale method to produce high-mobility, low-disorder 2DEG in $^{28}$Si/SiGe heterostructures without an epitaxial Si cap, enhancing suitability for quantum computing applications.

Contribution

The authors introduce a novel growth process that omits the epitaxial Si cap, resulting in improved interface quality and uniform high-mobility 2DEG across a 100 mm wafer.

Findings

High mean mobility of (1.8±0.5)×10^5 cm^2/Vs at 1.7 K

Low mean percolation density of (9±1)×10^{10} cm^{-2}

Reduced scattering indicating low-disorder environment

Abstract

We grow $^{28}$Si/SiGe heterostructures by reduced-pressure chemical vapor deposition and terminate the stack without an epitaxial Si cap but with an amorphous Si-rich layer obtained by exposing the SiGe barrier to dichlorosilane at 500 {\deg}C. As a result, $^{28}$Si/SiGe heterostructure field-effect transistors feature a sharp semiconductor/dielectric interface and support a two-dimensional electron gas with enhanced and more uniform transport properties across a 100 mm wafer. At T = 1.7 K we measure a high mean mobility of (1.8$\pm$0.5)$\times$10$^5$ cm$^2$/Vs and a low mean percolation density of (9$\pm$1)$\times$10$^{10}$ cm$^{-2}$. From the analysis of Shubnikov-de Haas oscillations at T = 190 mK we obtain a long mean single particle relaxation time of (8.1$\pm$0.5) ps, corresponding to a mean quantum mobility and quantum level broadening of (7.5$\pm$0.6)$\times$10$^4$ cm$^{2}$/Vs and (40$\pm$3) $\mu$eV, respectively, and a small mean Dingle ratio of (2.3$\pm$0.2), indicating reduced scattering from long range impurities and a low-disorder environment for hosting high-performance spin-qubits.