Defect study of Zn-dopedp-type gallium antimonide using positron lifetime spectroscopy

Defects in p-type Zn-doped liquid-encapsulated Czochralski--grown GaSb were studied by the positron lifetime technique. The lifetime measurements were performed on the as-grown sample at temperature varying from 15 K to 297 K. A positron trapping center having a characteristic lifetime of 317 ps was identified as the neutral VGa-related defect. Its concentration in the as-grown sample was found to be in the range of 10¹⁷--10¹⁸ cm^-3. At an annealing temperature of 300^∘C, the VGa-related defect began annealing out and a new defect capable of trapping positrons was formed. This newly formed defect, having a lifetime value of 379 ps, is attributed to a vacancy--Zn-defect complex. This defect started annealing out at a temperature of 580^∘C. A positron shallow trap having binding energy and concentration of 75 meV and 10¹⁸ cm^-3, respectively, was also observed in the as-grown sample. This shallow trap is attributed to positrons forming hydrogenlike Rydberg states with the ionized dopant acceptor Zn.