Dynamics of ground and excited states of bound excitons in gallium nitride

Time-resolved photoluminescence measurements of high-quality GaN show that the spectra of two-electron satellites (TES) in GaN include also lines coming from excited states of a donor-bound exciton (D0X) complex. The lines connected with recombination from the ground and excited states have generally similarly long lifetimes (1.1-1.4 ns, in the case of an exciton bound to oxygen donor). However, analysis of initial dynamics (between 0 and 0.5 ns) shows some transfer of energy between the lines. In fact, the ground-state-related line reaches its maximum 0.1 ns after the excited-state-related line. A rate-equation model taking into account internal transitions in the D0X complex gives a characteristic internal time constant of about 0.2 ns.