Professor Robert Taylor

Abstract:

Microphotoluminescence with one-photon and two-photon excitation has been employed to investigate localisation centres found in nanorod array LEDs. Quantum dot-like features with spectral width less than 1 meV were observed originating from low dimensional carrier confinement within the nanorods. Two-photon excitation was used to probe the individual localisation centres. The narrow peak PL energy does not shift with increasing excitation density, but rather an increase of discrete new peaks on the high energy side of the spectrum is observed. There is no temperature dependent emission energy shift observed from 4.3 K to 25 K. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Abstract:

We report on the growth (using metal-organic vapour phase epitaxy) and optical characterisation of single and multiple layers of InGaN quantum dots (QDs), which were formed by annealing InGaN epilayers at the growth temperature in nitrogen. The size and density of the nanostructures have been found to be fairly similar for uncapped single and three layer QD samples if the GaN barriers between the dot layers are grown at the same temperature as the InGaN epilayer. The distribution of nanostructure heights of the final QD layer of three is wider and is centred around a larger size if the GaN barriers are grown at two temperatures (first a thin layer at the dot growth temperature, then a thicker layer at a higher temperature). Micro-photoluminescence studies at 4.2 K of capped samples have confirmed the QD nature of the capped nanostructures by the observation of sharp emission peaks with full width at half maximum limited by the resolution of the spectrometer. We have also observed much more QD emission per unit area in a sample with three QD layers, than in a sample with a single QD layer, as expected. © 2011 Elsevier B.V. All rights reserved.