D- shallow donor near a semiconductor-metal and a semiconductor-dielectric interface

TL;DR

This study investigates how the proximity of a negatively charged donor (D-) to semiconductor-metal and semiconductor-dielectric interfaces affects its binding energy and wavefunction, revealing enhanced binding near metal interfaces and reduced binding near dielectric ones.

Contribution

It introduces a variational approach considering image charges and electron correlation to analyze D- states near interfaces, providing new insights into interface effects on donor binding energies.

Findings

D- binding energy increases near metal interfaces for d>1.5a_B

Binding energy decreases and D- becomes unbound as it approaches interfaces

System behavior differs significantly between metal and dielectric interfaces

Abstract

The ground state energy and the extend of the wavefunction of a negatively charged donor (D-) located near a semiconductor-metal or a semiconductor-dielectric interface is obtained. We apply the effective mass approximation and use a variational two-electron wavefunction that takes into account the influence of all image charges that arise due to the presence of the interface, as well as the correlation between the two electrons bound to the donor. For a semiconductor-metal interface, the D- binding energy is enhanced for donor positions d>1.5a_B (a_B is the effective Bohr radius) due to the additional attraction of the electrons with their images. When the donor approaches the interface (i.e. d<1.5a_B) the D- binding energy drops and eventually it becomes unbound. For a semiconductor-dielectric (or a semiconductor-vacuum) interface the D- binding energy is reduced for any donor position as compared to the bulk case and the system becomes rapidly unbound when the donor approaches the interface.