Weak Antilocalization of Two-Dimensional Hole Gases in a Modulation-Doped GeSn/Ge Heterostructure

GeSn shows strong Rashba spin-orbit coupling (SOC) and is a promising material for quantum and spintronics applications, such as fast spin qubits and spin field-effect transistors. In this work, we demonstrate weak antilocalization (WAL) in modulation-doped GeSn_0.94Sn_0.06/Ge heterostructure. We characterize the carrier transport properties by performing Hall measurements at 40 mK with the highest mobility of ~ 32,000 cm²/V-s. We observe WAL patterns at a carrier density of 3.3 x 10¹¹ cm^-2. By fitting WAL patterns to the Hikami-Larkin-Nagaoka (HLN) model, we extract spin relaxation time (~ 14 ps) and length (~ 0.67 μm). We also observe clear quantum Hall plateaus and Shubnikov-de Haas (SdH) oscillations starting from a filling factor of 22 at a magnetic field of 0.67 T. The longitudinal resistance reaches zero at filling factors of 4 and 2, indicating the high material quality of the GeSn/Ge heterostructure. We show that there is no parallel conduction in this modulation-doped heterostructure by comparing the carrier densities from the low-field measurements and fast Fourier transform of the data of SdH oscillations.