Identification of donor-related impurities in ZnO using photoluminescence and radiotracer techniques

The results of photoluminescence measurements on ZnO implanted with stable and radioactive isotopes of Zn and Ga are presented. The donor-related exciton feature ${I}_{8}$ at $3.3600\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ is suggested to be due to bound exciton recombination at Ga donors. The ${I}_{1}$ line at $3.3718\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ is also likely to be due to Ga, and is attributed to ionized Ga donor bound exciton recombination. A feature at $3.3225\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ is observed following transmutation of radioactive Ga into stable Ge, and is attributed to Ge. Finally, a damage-related band is observed in the region of $1.8\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ when the recoil energy of the decay is capable of dislodging the host atoms from their respective lattice sites.