Direct observation of site-specific dopant substitution in Si doped (AlxGa1-x)2O3 via Atom Probe Tomography

TL;DR

This study uses atom probe tomography to analyze how silicon dopants distribute and occupy sites in (AlxGa1-x)2O3 films across the entire composition range, revealing site preferences and inhomogeneities.

Contribution

It provides the first detailed atomistic insight into dopant site preferences and distribution in (AlxGa1-x)2O3 films over the full composition spectrum.

Findings

Dopant distribution is nearly uniform with densities around 10^18 cm^-3.

Si prefers Ga sites at low Al content and Al sites at high Al content.

In the intermediate Al range, Si occupies either site due to layer inhomogeneity.

Abstract

In this work, the interaction of n-type dopants in Si doped (AlxGa1-x)2O3 films with varying Al content over the entire composition range (x = 0-100%) was analyzed using atom probe tomography. An almost uniform dopant distribution with dopant density in the range of 1018 cm-3 was obtained in all (AlxGa1-x)2O3 layers containing different Al contents. We have demonstrated that for the single phase \b{eta}-(AlxGa1-x)2O3 films with Al content of x<0.30, dopants prefer to occupy on Ga sites while Al site is preferred for high Al content (x>0.50) (AlxGa1-x)2O3 layers. It was also observed for Al content, x = 0.30-0.50, no specific cationic site occupancy was observed, Si occupies either Al or Ga sites. This can be attributed to highly inhomogeneous layers within this composition range due to which dopant Si atoms are either in the Al-rich or Al-depleted regions.