High quality gallium doped ZnO (Ga:ZnO) thin films were grown on c- Al2 O3 (1000) by plasma-assisted molecular beam epitaxy, and Ga concentration NGa was controlled in the range of 1× 1018 -2.5× 1020 cm3 by adjustingchanging the Ga cell temperature. From the low-temperature photoluminescence at 10 K, the donor bound exciton I8 related to Ga impurity was clearly observed and confirmed by comparing the calculated activation energy of 16.8 meV of the emission peak intensity with the known localization energy, 16.1 meV. Observed asymmetric broadening with a long tail on the lower energy side in the photoluminescence (PL) emission line shape could be fitted by the Stark effect and the compensation ratio was approximately 14-17% at NGa 1× 1020 cm3. The measured broadening of photoluminescence PL emission is in good agreement with the total thermal broadening and potential fluctuations caused by random distribution of impurity at NGa lower than the Mott critical density.
ASJC Scopus subject areas
- Physics and Astronomy(all)