# Unusual anisotropy of inplane field magnetoresistance in ultra-high mobility SiGe/Si/SiGe quantum wells

## TL;DR

This paper reports an unusual anisotropy in in-plane field magnetoresistance in ultra-high mobility SiGe/Si/SiGe quantum wells, linked to surface ridges and crystallographic orientation, with a method to relate different measurement configurations.

## Contribution

It introduces a novel understanding of anisotropic magnetoresistance caused by surface ridges and provides a recalculation method to compare different measurement orientations.

## Key findings

- Anisotropy depends on orientation between magnetic field and current.
- A recalculation method aligns measurements at different orientations.
- Results agree with experimental data.

## Abstract

We find an unusual anisotropy of the inplane field magnetoresistance in ultra-high mobility SiGe/Si/SiGe quantum wells. The anisotropy depends on the orientation between the inplane field, $B_\parallel$, and current, $I$, relative to the crystallographic axes of the sample and is a consequence of the intrinsic ridges on the quantum well surface. For the simplest orientations between current and crystallographic axes, a method of recalculating the magnetoresistance measured at $I\perp B_\parallel$ into the one measured at $I\parallel B_\parallel$ is suggested and is shown to yield results that agree with the experiment.