Impacts of Si-doping on vacancy complex formation and their influences on deep ultraviolet luminescence dynamics in AlxGa1−xN films and multiple quantum wells grown by metalorganic vapor phase epitaxy

Abstract

To find a clue to increase the emission efficiencies of AlxGa1−xN-based deep ultraviolet light emitters, the origins and influences on carrier concentration and minority carrier lifetime (tminority), which determines the internal quantum efficiency, of midgap recombination centers in c-plane Si-doped Al0.60Ga0.40N epilayers and Al0.68Ga0.32N quantum wells (QWs) grown by metalorganic vapor phase epitaxy were studied by temporally and spatially resolved luminescence measurements, making a correlation with the results of positron annihilation measurement. For the Al0.60Ga0.40N epilayers, tminority decreased as the concentration of cation vacancies (VIII) increased, indicating that VIII, most probably decorated with nitrogen vacancies (VN), VIII(VN)n, are major nonradiative recombination centers (NRCs). For heavily Si-doped Al0.60Ga0.40N, a generation of electron-compensating complexes (VIII–SiIII) is suggested. For the lightly Si-doping regime, tminority of the QW emission was increased by appropriate Si-doping in the wells, which simultaneously increased the terrace width. The importance of wetting conditions is suggested for decreasing the NRC concentration.