Ga2SeTe2 belongs to a family of materials with large intrinsic vacancy
concentrations that are being actively studied due to their potential for
diverse applications that include thermoelectrics and phase-change memory. In
this article, the Ga2SeTe2 structure is investigated via synchrotron x-ray
diffraction, electron microscopy, and x-ray absorption experiments. Diffraction
and microscopy measurements showed that the extent of vacancy ordering in
Ga2SeTe2 is highly dependent on thermal annealing. It is posited that
stoichiometric vacancies play a role in local atomic distortions in Ga2SeTe2
(based on the fine structure signals in the collected x-ray absorption
spectra). The effect of vacancy ordering on Ga2SeTe2 material properties is
also examined through band gap and Hall effect measurements, which reveal that
the Ga2SeTe2 band gap redshifts by ~0.05 eV as the vacancies order and
accompanied by gains in charge carrier mobility. The results serve as an
encouraging example of altering material properties via intrinsic structural
rearrangement as opposed to extrinsic means such as doping.