Gallium vacancy and the residual acceptor in undoped GaSb studied by   positron lifetime spectroscopy and photoluminescence
  Positron lifetime, Photoluminescence and Hall measurements were performed to study undoped p-type gallium antimonide materials. A 314ps lifetime component, attributed to $V_{Ga}$ related defect, was identified in the positron lifetime measurement. In the PL measurement, a $778meV$ and a $797meV$ peaks were observed. Isochronal annealing studies were performed and at the temperature of $300^{o}C$, both the 314ps positron lifetime component and the two PL signals disappeared, which gives a clear and strong evidence for their correlation. However, the hole concentration ($\sim 2\times 10^{17}cm^{-3}$) was observed to be constant throughout the whole annealing temperature range up to $500^{o}C$. Contradictory to general belief, this implies, at least for samples with annealing temperatures above $300^{o}C$, the Ga vacancy is not the acceptor responsible for the p-type conduction. 
C. C. Ling (1), W. K. Mui (1), C. H. Lam (1), C. D. Beling (1), S.   Fung (1), M. K. Lui (1), K. W. Cheah (2), K. F. Li (2),...