Subpicosecond luminescence spectroscopy of exciton localization in In_xGa_(1-x)N films

摘要

We have studied the exciton localization dynamics in In_xGa_(1-x)N epitaxial films with different In compositions (x=0.02, 0.05, and 0.09) by means of optical Kerr-gate time-resolved photoluminescence (PL) spectral measurements. By changing excitation wavelength of 150 fs laser pulses, In_xGa_(1-x)N films are resonantly excited around their exciton energies at 6 K. Under the resonant excitation, the PL dynamics is sensitive to the In composition of the sample and the excitation laser intensity. In the low In composition samples, the formation time of radiative excitons at localized states is 5-10 ps. In the high In composition samples, the gradual redshift of the PL peak energy is observed within several tens of picoseconds. The radiative recombination processes of excitons are discussed.