# Probing the local electronic structure of isovalent Bi atoms in InP

## TL;DR

This study uses cross-sectional scanning tunneling microscopy and theoretical calculations to analyze how isovalent Bi atoms affect the local electronic structure of InP, revealing anisotropic impurity states and band edge shifts.

## Contribution

It provides detailed experimental and theoretical insights into the spatial electronic effects of Bi impurities in InP, including impurity state structure and band modifications.

## Key findings

- Bi creates anisotropic bowtie-like impurity states
- Bi induces a resonant state in the valence band
- Band edge shifts depend on Bi atom position

## Abstract

Cross-sectional scanning tunneling microscopy (X-STM) is used to experimentally study the influence of isovalent Bi atoms on the electronic structure of InP. We map the spatial pattern of the Bi impurity state, which originates from Bi atoms down to the sixth layer below the surface, in topographic, filled state X-STM images on the natural $\{110\}$ cleavage planes. The Bi impurity state has a highly anisotropic bowtie-like structure and extends over several lattice sites. These Bi-induced charge redistributions extend along the $\left\langle 110\right\rangle$ directions, which define the bowtie-like structures we observe. Local tight-binding calculations reproduce the experimentally observed spatial structure of the Bi impurity state. In addition, the influence of the Bi atoms on the electronic structure is investigated in scanning tunneling spectroscopy measurements. These measurements show that Bi induces a resonant state in the valence band, which shifts the band edge towards higher energies. This is in good agreement to first principles calculations. Furthermore, we show that the energetic position of the Bi induced resonance and its influence on the onset of the valence band edge depend crucially on the position of the Bi atoms relative to the cleavage plane.