Single Crystal Growth of Ga2(SexTe1-x)3 Semiconductors and Defect   Studies via Positron Annihilation Spectroscopy
  Small single crystals of Ga2(SexTe1-x)3 semiconductors, for x = 0.1, 0.2, 0.3, were obtained via modified Bridgman growth techniques. High-resolution powder x-ray diffractometry confirms a zincblende cubic structure, with additional satellite peaks observed near the (111) Bragg line. This suggests the presence of ordered vacancy planes along the [111] direction that have been previously observed in Ga2Te3. Defect studies via positron annihilation spectroscopy show an average positron lifetime of ~400 ps in bulk as-grown specimens. Such a large lifetime suggests that the positron annihilation sites in these materials are dominated by defects. Moreover, analyzing the electron momenta via coincidence Doppler broadening measurements suggests a strong presence of large open-volume defects, likely to be vacancy clusters or voids. 
N. M. Abdul-Jabbar, E. D. Bourret-Courchesne, B. D. Wirth
cond-mat.mtrl-sci