Fine structure of neutral acceptor states of isolated impurity in zinc-blende semiconductors

TL;DR

This paper re-examines neutral acceptor states in zinc-blende semiconductors using an extended tight-binding model, clarifying symmetry issues, analyzing effects of strain and electric fields, and exploring impurity fine structure relevant for STM imaging.

Contribution

It introduces a detailed atomistic analysis of acceptor states, resolving symmetry discrepancies and examining impurity fine structure under strain and electric fields.

Findings

Symmetry discrepancy explained by potential over-symmetrization in k·p models.

Strain and electric fields lift degeneracy and alter LDOS.

Exchange interaction affects impurity state isotropy.

Abstract

The properties of neutral acceptor states in zinc-blende semiconductors are re-examined in the frame of extended-basis $sp^3d^5s^*$ tight-binding model. The symmetry discrepancy between envelope function theory and atomistic calculations is explained in terms of over symmetric potential in current k$\cdot$p approaches. Spherical harmonics decomposition of microscopic Local Density Of States (LDOS) allows for the direct analysis of the tight-binding results in terms of envelope function. Lifting of degeneracy by strain and electric field and their effect on LDOS is examined. The fine structure of magnetic impurity caused by exchange interaction of hole with impurity $d$-shell and its dependence on strain is studied. It is shown that exchange interaction by mixing heavy and light hole makes the ground state more isotropic. The results are important in the context of Scanning Tunneling Microscopy (STM) images of subsurface impurities.