The deep-level defects which were responsible for the 2.4eV photoluminescence band in a free-standing GaN template were studied by means of transient photoluminescence. A non-exponential decay of the photoluminescence intensity, which was observed at low temperatures, was attributed to a donor-acceptor pair recombination which involved a shallow donor and a deep acceptor. At room temperature, a single-exponential photoluminescence decay, with a lifetime of 30μs, was observed on the high-energy side of the band. The second component, with a lifetime of about 750μs, was detected on the low-energy side of the band. The photoluminescence decay, and transformation of the photoluminescence spectrum at room temperature, were attributed to transitions from the conduction band to 2 deep acceptors. The electron-capture cross-section was estimated to be equal to 4 x 10-21 and 10-19cm2 for the yellow and green bands, respectively, which contributed to the broad 2.4eV band.

Transient Photoluminescence of Defect Transitions in Free-Standing GaN. M.A.Reshchikov, H.Morkoç, S.S.Park, K.Y.Lee: Applied Physics Letters, 2001, 78[19], 2882-4