Scattering anisotropy in HgTe (013) quantum well

TL;DR

This study investigates how electron transport anisotropy in HgTe (013) quantum wells varies with electron density, revealing significant anisotropy increases linked to subband transitions and interface roughness effects.

Contribution

It provides detailed experimental insights into the density-dependent anisotropy in HgTe quantum wells and links it to intra- and inter-subband scattering mechanisms.

Findings

Anisotropy absent near charge neutrality point.

Anisotropy increases with electron density, reaching 10%.

Sharp increase to 60% anisotropy at second subband.

Abstract

We report on a detailed experimental study of the electron transport anisotropy in HgTe (013) quantum well of 22 nm width in the directions $[100]$ and $[03\bar{1}]$ as the function of the electron density $n$. The anisotropy is absent at minimal electron density near the charge neutrality point. The anisotropy increases with the increase of n and reaches about 10% when the Fermi level is within the first subband H1. There is a sharp increase of the anisotropy (up to 60%) when the Fermi level reaches the second subband E2. We conclude that the first effect is due to the small intra-subband anisotropic interface roughness scattering, and the second one is due to the strongly anisotropic inter-subband roughness scattering, but the microscopical reason of such a strong change in the anisotropy remains unknown.