Influence of silicon doping on vacancies and optical properties of $AlxGa1−xN$ thin films

The authors have used positron annihilation spectroscopy and photoluminescence measurements to study the influence of silicon doping on vacancy formation in AlGaN:Si structures. The results show a correlation between the Doppler broadening measurements and the intensity from $510nm$ photoluminescence transition. The reduction in the $W$ parameter when the $[Si]∕[Al+Ga]$ fraction in the gas phase is above $3×10−4$ indicates that the positrons annihilate in an environment where less Ga $3d$ electrons are present, i.e., they are trapped in group-III vacancies. The observation of vacancies at these silicon concentrations coincides with the onset of the photoluminescence transition at $510nm$⁠.