Dresden 2009 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 17: Quantum wires: Optical and transport properties

HL 17.2: Talk

Tuesday, March 24, 2009, 10:15–10:30, BEY 154

Optical Studies on Single GaN Nanowires — •Carsten Pfüller, Oliver Brandt, Caroline Chèze, Lutz Geelhaar, and Henning Riechert — Paul-Drude-Institut für Festkörperelektronik Berlin, Germany

The self-organized formation of GaN nanowires (NWs) offers the unique possibility to fabricate strain- and defect-free GaN crystals on foreign substrates like Si. Here, we present a detailed investigation of the photoluminescence (PL) of GaN NWs grown directly on Si(111) by plasma-assisted molecular beam epitaxy.

The temperature and power-dependent PL spectra of the NW ensemble are compared with those of a reference layer grown by hydride vapor phase epitaxy. The spectral position of the dominant donor-bound exciton emission at 3.472 eV demonstrates the NWs to be free of strain. The evolution of the PL intensity with temperature or excitation intensity for the NWs is clearly different from that of the reference layer, indicating the participation of different nonradiative recombination channels possibly related to the free surface.

For a more detailed understanding, we have examined the PL of individual NWs which have been dispersed on a Si(111) substrate. The spectra of single NWs vary widely from wire to wire in intensity, peak energy and peak width. The frequently observed peak broadening compared to the ensemble reveals that individual NWs may be severely affected by strain induced by the interaction with the underlying substrate.