Picosecond dynamics of excitons in cubic GaN

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Abstract
Using time-resolved photoluminescence, we investigate the spectral and temporal behavior of the near-band-edge emission located at 3.255–3.27 eV of cubic GaN/GaAs(001) grown by plasma-assisted molecular-beam epitaxy. In contrast to transitions at lower energies, this narrow high-energy emission band exhibits an ultrafast dynamics on a picosecond time scale. The decay is characterized by a biexponential behavior composed of a fast initial component (15–40 ps) followed by a second, slower component (100–400 ps). We attribute the initial decay to radiative decay of free excitons and the relaxation towards bound states. The second slower component is assigned to the radiative recombination of these bound excitons. This interpretation is supported by intensity-dependent measurements.