Realization of Very High Mobility InAs Quantum Wells on InP Substrates Through Convex InAlAs Graded Buffer Optimization
Due to strong spin-orbit coupling, large Landé $g$-factor, and a highly transparent interface, the two-dimensional electron gas (2DEG) in InAs quantum wells provides an ideal platform for the exploration of topological superconductivity in hybrid semiconductor-superconductor heterostructures. Reduction of disorder in the semiconductor remains a primary challenge to the disambiguation of subtle interaction effects. Here we demonstrate very high mobility InAs 2DEGs grown on insulating InP substrates. Utilizing a convex compositional grading profile in an InAlAs metamorphic buffer we demonstrate InAs quantum wells with thickness greater than 10 nm without need of Ga-containing cladding layers. We examine structural and electrical transport properties of these heterostructures. Advances in the design of the metamorphic InAlAs buffer result in low-temperature electron mobility exceeding $1.7\times10^6$ cm$^2$ V$^{-1}$ s$^{-1}$ at 2DEG density $\leq3.2\times10^{11}$ cm$^{-2}$, the highest value yet reported for this material system.