Macroscopic polarization and band offsets at nitride heterojunctions

TL;DR

This study uses ab initio methods to analyze polar interfaces in nitride heterojunctions, revealing large electric fields and asymmetrical band offsets that impact electronic properties.

Contribution

It introduces new techniques to evaluate band offsets and formation energies in polar nitride heterojunctions, accounting for polarization effects.

Findings

Large electric fields exist in nitride overlayers due to polarization discontinuity.

Significant asymmetry in band offsets at heterojunctions.

Tiny interface formation energies indicating stable interfaces.

Abstract

Ab initio electronic structure studies of prototypical polar interfaces of wurtzite III-V nitrides show that large uniform electric fields exist in epitaxial nitride overlayers, due to the discontinuity across the interface of the macroscopic polarization of the constituent materials. Polarization fields forbid a standard evaluation of band offsets and formation energies: using new techniques, we find a large forward-backward asymmetry of the offset (0.2 eV for AlN/GaN (0001), 0.85 eV for GaN/AlN (0001)), and tiny interface formation energies.