Origin of shallow n-type doping in AlN and Al-rich AlGaN

TL;DR

This paper investigates the origin of shallow n-type doping in AlN by combining defect calculations and structural searches, revealing metastable aluminum interstitials as key donors, which advances understanding of doping mechanisms in ultrawide bandgap semiconductors.

Contribution

It introduces a novel approach combining defect calculations with structural searches to identify metastable donor configurations in AlN, expanding doping strategies.

Findings

Al interstitials can act as shallow donors in metastable states

Metastable defect configurations significantly influence n-type doping

New insights into defect behavior improve doping control in AlN

Abstract

Achieving efficient n-type doping in AlN, a representative ultrawide bandgap (UWBG) semiconductor, remains a longstanding challenge that limits its application in high-power electronics and deep-ultraviolet optoelectronics. Conventional dopants in AlN often introduce deep levels or form compensating complexes, leading to low free-carrier concentrations. In this work, we combine first-principles defect calculations with a structural search method tailored to explore metastable configurations to systematically investigate donor-type defects in AlN. Our results reveal that the aluminum interstitial ($Al_i$) can exhibit shallow-donor behavior in specific metastable configurations that were previously overlooked. This discovery expands the understanding of n-type dopability in AlN, and highlights the critical role of metastable defects in modulating electronic properties.