Time-resolved photoluminescence studies of an ionized donor-bound exciton in GaN

Time-resolved photoluminescence (PL) spectroscopy has been used to study th e radiative recombination of excitons bound to ionized donors in GaN doped with both Mg and Si at concentrations of 5x10(18)/cm(3) and 1.5x10(17)/cm(3 ) respectively. Low temperature (T similar to 10K) time-resolved, as well a s integrated PL spectra, identify an ionized donor-bound (Si) exciton peak (D+X) approximately 11.5 meV below and a neutral acceptor-bound exciton (A( 0)X) 20.5 meV below the free exciton peak. Rapid decay of the free exciton emission (less than or equal to 20 ps) implies that excitons are quickly ca ptured by accepters and ionized donors. We find the (AOX) emission lifetime is consistent with previous measurements for GaN:Mg epilayers, while the ( D+X) lifetime of 160 ps is longer than that of the well studied neutral don or-bound exciton ((DX)-X-0). The measured (D+X) lifetime, in comparison wit h ((DX)-X-0) and (A(0)X), suggests that the state is stable at low temperat ure. (C) 1999 American Institute of Physics. [S0003-6951(99)03604-9].