Influence of the exchange reaction on the electronic structure of GaN/Al junctions

TL;DR

This study uses ab-initio calculations to analyze how interface structure and exchange reactions influence the electronic properties and Schottky barrier height of Al/GaN junctions, finding minimal impact from certain atomic modifications.

Contribution

It provides a detailed theoretical analysis of how exchange reactions and interface morphology affect the electronic structure of Al/GaN interfaces, highlighting the robustness of the Schottky barrier against specific atomic changes.

Findings

Intermixed interfaces do not significantly alter Fermi level pinning.

Interface band alignment is relatively insensitive to morphology changes.

Ultrathin intralayers and atomic swaps have minimal effect on SBH.

Abstract

Ab-initio calculations have been used to study the influence of the interface morphology and, notably, of the exchange reaction on the electronic properties of Al/GaN (100) interfaces. In particular, the effects of interface structure (i.e. interfacial bond lengths, semiconductor surface polarity, and reacted intralayers) on the SBH at the Al/GaN (001) junction are specifically addressed. The electronic structure of the following atomic configurations have been investigated theoretically: (i) an abrupt, relaxed GaN/Al interface; (ii) an interface which has undergone one monolayer of exchange reaction; and interfaces with a monolayer-thick interlayer of (iii) AlN and (iv) Ga$_{0.5}$Al$_{0.5}$N. Intermixed interfaces are found to pin the interface Fermi level at a position not significantly different from that of an abrupt interface. Our calculations also show that the interface band line--up is not strongly dependent on the interface morphology changes studied. The p-type SBH is reduced by less than 0.1 eV if the GaN surface is Ga-terminated compared to the N-terminated one. Moreover, we show that both an ultrathin Ga$_x$Al$_{1-x}$N ($x$ = 0, 0.5) intralayer and a Ga$\leftrightarrow$Al atomic swap at the interface does not significantly affect the Schottky barrier height.