Positron annihilation spectroscopy was used to study the point defects that were introduced by 2MeV electron irradiation (6 x 1017/cm2) of single-crystal n-type samples. The positron lifetime measurements showed that Zn vacancies in their doubly negative charge state, which acted as dominant compensating centers in the as-grown material, were produced during irradiation. Their contribution to electrical compensation was important. Lifetime measurements also revealed the presence of competing positron traps with low binding energy, and lifetime close to that of the bulk lattice. Analysis of Doppler broadening of the 511keV annihilation line indicated that these defects could be identified as being neutral O vacancies.

Irradiation-Induced Defects in ZnO Studied by Positron Annihilation Spectroscopy. Tuomisto, F., Saarinen, K., Look, D.C.: Physica Status Solidi A, 2004, 201[10], 2219-24