Strain Effects on Rashba Spin-Orbit Coupling of 2D Hole Gases in GeSn/Ge Heterostructures.

Tai, Chia-Tse; Chiu, Po-Yuan; Liu, Chia-You; Kao, Hsiang-Shun; Harris, C Thomas; Lu, Tzu-Ming; Hsieh, Chi-Ti; Chang, Shu-Wei et al. · Adv Mater · 2021

basic_science · Level V

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Abstract

A demonstration of 2D hole gases in GeSn/Ge heterostructures with a mobility as high as 20 000 cm<sup>2</sup> V<sup>-1</sup> s<sup>-1</sup> is given. Both the Shubnikov-de Haas oscillations and integer quantum Hall effect are observed, indicating high sample quality. The Rashba spin-orbit coupling (SOC) is investigated via magneto-transport. Further, a transition from weak localization to weak anti-localization is observed, which shows the tunability of the SOC strength by gating. The magneto-transport data are fitted to the Hikami-Larkin-Nagaoka formula. The phase-coherence and spin-relaxation times, as well as spin-splitting energy and Rashba coefficient of the k-cubic term, are extracted. The analysis reveals that the effects of strain and confinement potential at a high fraction of Sn suppress the Rashba SOC caused by the GeSn/Ge heterostructures.