Taming complexity of disordered γ-Ga2O3

Illustration of the atomic structure of the disordered spinel γ-Ga2O3
Illustration of the atomic structure of the disordered spinel γ-Ga2O3

CMI researchers at Lawrence Livermore National Laboratory conducted the research for this highlight

Innovation
Developed a detailed understanding of the influence of structural disorder on the electronic structure of γ-Ga2O3, which is crucial to provide a firm knowledge base for this and other disordered materials.


Achievement 
γ-Ga2O3 has four inequivalent gallium lattice sites that are partially occupied in an inherently disordered structure, yielding an immensely complex structure despite its deceptively simple cubic symmetry. First principles calculations were combined with machine learning to screen almost one million possible structures in 160-atom model cells, which are compared with experimentally measured photoemission and photoluminescence spectra of high-quality samples.

Significance and Impact: 

  • Developed informed statistical models of the correlations between atomic and electronic structure of γ-Ga2O3.
  • Reported detailed first-principles and experimental characterization of the electronic structure of high-quality films.
  • Inform further studies with knowledge of structure and stability of γ-Ga2O3 with how this phase may develop during growth, particularly alloys incorporating Al.

Hub Goal Addressed
Develop and apply tools for accelerated materials discovery utilizing computational techniques and machine learning.

High-resolution phase contrast image along the [110] projection for γ-Ga2O3 crystallized on a sapphire substrate. (c) Shows a STEM high-angle annular dark-field image of the same area. 
High-resolution phase contrast image along the [110] projection for γ-Ga2O3 crystallized on a sapphire substrate. (c) Shows a STEM high-angle annular dark-field image of the same area. 

L. E. Ratcliff et al., Tackling Disorder in γ-Ga2O3. Adv Mater, 2204217 (2022).