Magneto-optical characterization of GeSn and GeSn/SiGeSn heterostructures

Hole spin qubits in germanium (Ge)-based heterostructures have demonstrated their potential for scalable quantum information processing using all-electrical gate operations. Furthermore, the emerging material platform of germanium-tin (GeSn) can feature a direct bandgap, which makes it promising for establishing spin-photon interfaces for quantum networking. Here, we perform magneto-photoluminescence measurements of a Ge0.88Sn0.12/Si0.02Ge0.89Sn0.09 double quantum well using the double modulation Fourier transform infrared-based photoluminescence spectroscopy. Our measurements reveal theoretically expected diamagnetic shift at low magnetic fields as well as the linear trend of zeroth-level Landau quantization at higher fields and Zeeman-induced polarization-dependent energy shifts at +/- 12 T. We extract an effective g-factor of ~ 2 and an excitonic reduced mass of ~ 0.04 me consistent with previous estimations for heavy-hole {\Gamma}-valley excitons. The observation of sizable Zeeman splitting is consistent with strong spin-orbit interaction in Ge-based hole systems, which can enable electrically driven spin control. Our analysis can be adopted for studying and evaluating group-IV semiconductor heterostructures as hosts for hole spin qubits toward scalable quantum information processing.