Unusual Formation of Point Defect Complexes in the Ultra-wide Band Gap Semiconductor beta-Ga2O3

TL;DR

This study reveals the atomic-scale formation of unique point defect complexes in beta-Ga2O3, linking microscopic observations with theoretical predictions and showing how doping influences defect structures and electronic properties.

Contribution

First direct microscopic observation of unusual point defect complexes in beta-Ga2O3, confirming their role as deep traps and their formation mechanism influenced by Sn doping.

Findings

Point defect complexes involve cation interstitials and vacancies.

These complexes act as deep electronic traps within the band gap.

Sn doping increases vacancy concentration, facilitating complex formation.

Abstract

Understanding the unique properties of ultra-wide band gap semiconductors requires detailed information about the exact nature of point defects and their role in determining the properties. Here, we report the first direct microscopic observation of an unusual formation of point defect complexes within the atomic scale structure of beta-Ga2O3 using high resolution scanning transmission electron microscopy (STEM). Each complex involves one cation interstitial atom paired with two cation vacancies. These divacancy - interstitial complexes correlate directly with structures obtained by density functional theory, which predicts them to be compensating acceptors in beta-Ga2O3. This prediction is confirmed by a comparison between STEM data and deep level optical spectroscopy results, which reveals that these complexes correspond to a deep trap within the band gap, and that the development of the complexes is facilitated by Sn doping through the increase in vacancy concentration. These findings provide new insight on this emerging material's unique response to the incorporation of impurities that can critically influence their properties.