Professor Robert Taylor

Abstract:

Time-resolved and time-integrated microphotoluminescence studies at 4.2 K were performed on a single InGaN/GaN nanorod light emitting diode, fabricated in an array, on a wafer scale by nanoimprint lithography. Emission properties and carrier dynamics of the single nanorods are presented. Sharp peaks of 2 meV line-width were observed. The single nanorods possess longer decay rates than an unprocessed wafer at delay-times above 50 ns after excitation. The time evolution of the photoluminescence spectra implies that the slower decay times are due to surface related localisation near the perimeter of the nanorods, resulting in a spatial separation of the recombining carriers at low excitation densities. © 2013 American Institute of Physics.

Abstract:

We performed spectroscopic studies of a single GaAs quantum ring with an anisotropy in the rim height. The presence of an asymmetric localised state was suggested by the adiabatic potential. The asymmetry was investigated in terms of the polarization dependence of excitons and biexcitons, where a large energy difference (∼ 0.8 meV) in the exciton emission energy for perpendicular polarizations was observed and the oscillator strengths were also compared using the photoluminescence decay rate. For perpendicular polarizations, the biexciton exhibits twice the energy difference seen for the exciton, a fact that may be attributed to a possible change in the selection rules for the lowered symmetry. © 2013 American Institute of Physics.