Dresden 2011 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 62: Nitrides: Advanced Characterization Techniques

HL 62.5: Talk

Wednesday, March 16, 2011, 16:15–16:30, POT 51

Time correlated single Photon Counting on GaN nanowires — •Aram Gorgis, Timur Flissikowski, Carsten Pfüller, Oliver Brandt, and Holger T. Grahn — Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin

GaN nanowires (GaN NWs) received much interest in the last years because they can be grown in excellent quality on foreign substrates such as Si. We have investigated the photoluminescence (PL) of GaN NW ensembles as well as of single GaN NWs in the time domain. For the ensemble, we find the PL transients to be non-exponential even for low excitation densities. This observation agrees with the reports of several other groups.

The NWs constituting the ensemble experience a size distribution, hence the surface-to-volume-ratio can vary significantly from NW to NW. Surface recombination, being inversely proportional to the NW diameter, is thus expected to contribute more to the PL decay of thin NWs than for thick ones. Consequently, the PL decay from a single NW should be exponential, but the decay time may differ from NW to NW.

To obtain PL transients of single, freestanding NWs from the same sample with a high dynamic range, we utilize time-correlated single photon counting which allows even very weak signals to be detected with high signal-to-noise ratio. For all single NWs investigated, we indeed observe a single exponential decay.