Photoluminescence decay in the ps time regime and structural properties of pulsed-laser deposited GaN

摘要

In this work we focus on the study of the fast photoluminescence decay in the ps time regime in comparison with structural properties of GaN films deposited by a cyclic pulsed laser deposition technique. Structural film properties are obtained from X-ray analysis and atomic force microscopy. Steady-state photoluminescence performed at 13 K shows the typical donor-bound excitonic transition (D~0X) at 3.47 eV and a line near 3.42 eV which can be related to structural defects. Fast fluorescence decays were obtained after excitation at 287 nm (4.32 eV) with 5 ps pulses from a frequency-doubled cavity-dumped dye laser. At room temperature the decay of the blue fluorescence at 367 nm showed decay times between 4 and 40 ps, whereas the yellow contribution at 530 nm could best be described by a multi-exponential fit with decay times of several ns. The results are compatible with published exciton decay times in epitaxial MOCVD-grown GaN films.