Luminescence of bound excitons in ZnO:Zn phosphor powders

Luminescence and time-resolved luminescence spectra of ZnO:Zn phosphor powders have been investigated at low temperatures. ZnO:Zn phosphor powders under the band-to-band excitation exhibit two prominent luminescence lines attributed to the radiative recombination of bound excitons at 3.360 and 3.365 eV. The luminescence line at 3.360 eV originates from an exciton bound to an intrinsic defect serving as a neutral donor. It is found that the luminescence line at 3.365 eV has a short decay time of ∼80 ps, and shows a long tail toward the lower energy side of the spectral peak. The origin of the luminescence line at 3.365 eV is discussed in terms of bound excitons associated with surface defect states in ZnO:Zn phosphor.