# First principles study of hBN-AlN short-period superlattice heterostructures

## TL;DR

This study uses first-principles calculations to explore how the structural, electronic, and optical properties of hBN-AlN superlattices vary with layer thickness, revealing phase transitions, interface effects, and optical activity.

## Contribution

It provides a detailed theoretical analysis of short-period hBN-AlN superlattices, highlighting the dependence of properties on AlN layer thickness and interface phenomena.

## Key findings

- Insulating behavior with small optical gaps for thin AlN layers
- Wurtzite phase formation in thicker AlN layers
- Presence of optically active defect-like states at interfaces

## Abstract

We report a theoretical study of the structural, electronic and optical properties of hBN-AlN superlattice heterostructures (SL) using a first-principles approach based on standard and hybrid Density Functional Theory. We consider short-period ($L<10$ nm) SL and find that their properties depend strongly on the AlN layer thickness $L_{AlN}$. For $L_{AlN}\lesssim1$ nm, AlN stabilizes into the hexagonal phase and SL display insulating behavior with type II interface band alignment and optical gaps as small as $5.2$ eV. The wurtzite phase forms for thicker AlN layers. In these cases built-in electric fields lead to formation of polarization compensating charges as well as two-dimensional conductive behavior for electronic transport along interfaces. We also find defect-like states localized at interfaces which are optically active in the visible range.