Quantum transport in high-quality shallow InSb quantum wells

InSb is one of the promising candidates to realize a topological state through proximity induced superconductivity in a material with strong spin–orbit interactions. In two-dimensional systems, thin barriers are needed to allow strong coupling between superconductors and semiconductors. However, it is still challenging to obtain a high-quality InSb two-dimensional electron gas in quantum wells close to the surface. Here, we report on a molecular beam epitaxy grown heterostructure of InSb quantum wells with substrate-side Si-doping and ultrathin InAlSb (5 nm, 25 nm, and 50 nm) barriers to the surface. We demonstrate that the carrier densities in these quantum wells are gate-tunable and electron mobilities up to 350 000 cm2(V s)−1 are obtained from magnetotransport measurements. Furthermore, from temperature-dependent magnetoresistance measurements, we obtain an effective mass of 0.02 m0 and find Zeeman splitting compatible with the expected band edge g-factor.