Shubnikov–de Haas Quantum Oscillations with Large Spin Splitting in High-Mobility Al_0.8Ga_0.2Sb/InAs/Al_0.8Ga_0.2Sb Quantum-Well Heterostructures

We report the epitaxial growth of high-quality Al_0.8Ga_0.2Sb/InAs/Al_0.8Ga_0.2Sb quantum well films characterized by high carrier mobility and strong spin–orbit coupling. By appropriately optimizing the Al-to-Ga ratio in the AlGaSb barrier layer, the quantum confinement of the heterostructure is significantly enhanced. Alongside a giant magnetoresistance ratio of 3.65 × 10⁵%, the two-carrier transport model from Hall measurements reveals an ultra-high electron mobility of 7.18 × 10⁵ cm²·V^-1·s^-1 at low temperatures. Meanwhile, pronounced Shubnikov–de Haas (SdH) quantum oscillations persist up to 30 K, and their single-frequency feature indicates a well-defined Fermi surface without subband mixing in the two-dimensional electron gas channel. Moreover, the large effective g-factor and tilted-field-induced orbital effect lead to the observation of split SdH peaks at large magnetic fields. Our results validate that AlGaSb/InAs quantum well heterostructures are suitable candidates for constructing energy-efficient topological spintronic devices.