Nanometer-scale sharpness in corner-overgrown heterostructures

TL;DR

This study demonstrates the ability to create extremely sharp corners in GaAs/AlGaAs heterostructures using molecular beam epitaxy, with potential applications in quantum nanostructures.

Contribution

It provides a detailed microscopy analysis and a quantitative model for self-limited corner growth in heterostructures, highlighting the preservation of nanometer-scale sharpness.

Findings

Corner profile width of 3.5 nm achieved

Self-ordered diagonal stripes observed at corners

Corner sharpness maintained after microns of growth

Abstract

A corner-overgrown GaAs/AlGaAs heterostructure is investigated with transmission and scanning transmission electron microscopy, demonstrating self-limiting growth of an extremely sharp corner profile of 3.5 nm width. In the AlGaAs layers we observe self-ordered diagonal stripes, precipitating exactly at the corner, which are regions of increased Al content measured by an XEDS analysis. A quantitative model for self-limited growth is adapted to the present case of faceted MBE growth, and the corner sharpness is discussed in relation to quantum confined structures. We note that MBE corner overgrowth maintains nm-sharpness even after microns of growth, allowing the realization of corner-shaped nanostructures.