Impacts of Si-doping and resultant cation vacancy formation on the luminescence dynamics for the near-band-edge emission of AI_(0.6)Ga_(0.4)N films grown on AlN templates by metalorganic vapor phase epitaxy

摘要

Luminescence dynamics for the near-band-edge (NBE) emission peak at around 250 nm of c-plane Si-doped Al_(0.6)Ga_(0.4)N films grown on AlN templates by low-pressure metalorganic vapor phase epitaxy were studied using deep ultraviolet time-resolved photoluminescence and time-resolved cathodoluminescence spectroscopies. For the films with the Si-doping concentration, [Si], lower than 1.9 × 10~(17)cm~(-3), the doping lessened the concentration of cation vacancies, [V_(Ⅲ)], through the surfactant effect or the aid of the reactant doping in a form of H_3SiNH_2. However, the room-temperature nonradiative lifetime, and, consequently, the equivalent value of internal quantum efficiency in the weak excitation regime steeply decreased when [Si] exceeded 10~(18)cm~(-3). Simultaneously, the intensity ratio of the deep-state emission band to the NBE emission abruptly increased. Because the increase in [Si] essentially gives rise to the increase in [V_(Ⅲ)] (for [Si] > 1.9 × 10~(17) cm~(3)) and the overcompensation of Si is eventually observed for the film with [Si] =4.0 × 10~(18)cm~(-3), the formation of acceptor-type native-defect complexes containing Si such as V_(Ⅲ)-Si_(Ⅲ) is suggested.