Quantum transport in high-quality shallow InSb quantum wells

Abstract

These authors contributed equally to this work. 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 ultra-thin 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 cm 2 (Vs) −1 are extracted from magneto-transport measurements. Furthermore, from temperature-dependent magneto-resistance measurements, we extract an effective mass of 0.02 m 0 and find a Zeeman splitting compatible with the expected band edge g-factor.

Electronic g factor and magnetotransport in InSb quantum wells

“…1 (g), the carrier density can be tuned from 2 × 10 JJ cm K8 to 3.5 × 10 JJ cm K8 while increasing the mobility from 1.3 × 10 5 cm 8 /(Vs) to 3 × 10 5 cm 8 /(Vs). The gate capacitance is estimated to be C = 0.32 mF/m 2 at the linear part of the n-VTG line, which is about 40% less than the value calculated from the plane-parallel capacitor model, which is similar to the results of our previous work [23].…”

“…The micro-fabrication process is similar to our previous work [23]. A standard Hall bar sample is defined using wet chemical etching with an etching depth of more than 270 nm, which is deeper than the Si δ-doping layer on the substrate side.…”

Electronic Structure and Epitaxy of CdTe Shells on InSb Nanowires

“…The equivalent mobilities for the CdTe shell and uncapped InSb nanowires indicate that the shell does not induce additional disorder to the InSb nanowires, thereby preserving the InSb nanowire properties. Possibly, thicker shells ( > 12 nm) are required to passivate the nanowire surface and further confine the electrons in the nanowire, similar to InSb quantum wells, where relatively thick barrier layers ( > 50 nm) are needed to achieve high mobility 42 . Nevertheless, thicker shells would not be compatible with a tunnel barrier at the interface between a semiconducting nanowire and a superconductor, seeing as the tunneling probability decreases exponentially with barrier thickness.…”

Strong and tunable spin–orbit interaction in a single crystalline InSb nanosheet

“…However, to build a device in which braiding of topological quantum states, such as Majorana fermions, can be conveniently performed and thus topological quantum computations can be designed and realized, it could be inevitable to move from single-nanowire structures to multiple-nanowire 20,21 and twodimensional (2D) planar quantum structures [22][23][24] . Recently, highquality InSb/InAlSb heterostructured quantum wells 25,26 and freestanding InSb nanosheets [27][28][29][30] have been achieved by epitaxial growth techniques. In comparison with InSb/InAlSb quantum well systems, the free-standing InSb nanosheets have advantages in direct contact by metals, including superconducting materials, in easy transfer to different substrates, and in convenient fabrication of dual-gate structures.…”