Split Ga vacancies and the unusually strong anisotropy of positron annihilation spectra in beta-Ga2O3

Karjalainen, Antti; Prozheeva, Vera; Simula, Kristoffer; Makkonen, Ilja; Callewaert, Vincent; Varley, Joel B.; Tuomisto, Filip

doi:10.1103/PHYSREVB.102.195207

Title

Split Ga vacancies and the unusually strong anisotropy of positron annihilation spectra in beta-Ga2O3

Author

Karjalainen, Antti

Prozheeva, Vera

Simula, Kristoffer

Makkonen, Ilja

Callewaert, Vincent

Varley, Joel B.

Tuomisto, Filip

Abstract

We report a systematic first-principles study on positron annihilation parameters in the beta-Ga2O3 lattice and Ga monovacancy defects complemented with orientation-dependent experiments of the Doppler broadening of the positron-electron annihilation. We find that both the beta-Ga2O3 lattice and the considered defects exhibit unusually strong anisotropy in their Doppler broadening signals. This anisotropy is associated with low symmetry of the beta-Ga2O3 crystal structure that leads to unusual kind of one-dimensional confinement of positrons even in the delocalized state in the lattice. In particular, the split Ga vacancies recently observed by scanning transmission electron microscopy produce unusually anisotropic positron annihilation signals. We show that in experiments, the positron annihilation signals in beta-Ga2O3 samples seem to be often dominated by split Ga vacancies.

Language

English

Source (journal)

Physical review B / American Physical Society. - New York, N.Y, 2016, currens

Publication

New York, N.Y : American Physical Society , 2020

ISSN

2469-9969 [online]

2469-9950 [print]

DOI

10.1103/PHYSREVB.102.195207

Volume/pages