Influence of surface-related strain and electric field on acceptor wave functions in Zincblende semiconductors

TL;DR

This study uses STM to analyze how surface strain and electric fields affect the shape and symmetry of acceptor wave functions in zincblende semiconductors, revealing depth-dependent asymmetries.

Contribution

It demonstrates the influence of surface-related strain and electric fields on acceptor wave functions, providing experimental validation of theoretical models.

Findings

Surface strain and electric fields cause asymmetry in acceptor wave functions.

Deeper acceptors (>10 layers) match bulk theoretical shapes.

Surface relaxation effects reduce symmetry near the surface.

Abstract

The spatial distribution of the local density of states (LDOS) at Mn acceptors near the (110) surface of p-doped InAs is investigated by Scanning Tunneling Microscopy (STM). The shapes of the acceptor contrasts for different dopant depths under the surface are analyzed. Acceptors located within the first ten subsurface layers of the semiconductor show a lower symmetry than expected from theoretical predictions of the bulk acceptor wave function. They exhibit a (001) mirror asymmetry. The degree of asymmetry depends on the acceptor atoms' depths. The measured contrasts for acceptors buried below the 10th subsurface layer closely match the theoretically derived shape. Two effects are able to explain the symmetry reduction: the strain field of the surface relaxation and the tip-induced electric field.