Professor Robert Taylor

Abstract:

We have investigated exciton dynamics in asymmetric GaN quantum discs embedded in AlGaN barriers with an Al content of 50% using time-integrated and time-resolved micro-photoluminescence measurements. Emission from the quantum discs emerges at lower energy than that from the GaN nanocolumns, which suggests that GaN quantum discs are strongly affected by the built-in electric field. The lifetimes of localized excitons in quantum discs were obtained. Nonlinear emission from quantum discs under high excitation power was attributed to tunneling of carriers to larger discs from smaller discs. © 2005 American Institute of Physics.

Abstract:

In x Ga 1-xN quantum dots have been fabricated by the selective growth of GaN micro-pyramid arrays topped with InGaN/GaN quantum wells. The spatially- and spectrally-resolved luminescence properties of these structures were measured using low-temperature micro-photoluminescence spectroscopy, The presence of InGaN quantum dots was confirmed directly by the observation of sharp peaks in the emission spectrum at the pyramid apices. These luminescence peaks exhibit linewidths down to 650 μeV (limited by the spectrometer resolution). We describe the broadening of the luminescence peak from a single dot as a function of temperature and excitation power. © 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Abstract:

By means of a 3D self-consistent numerical simulation we have calculated the wavefunctions and energies of the states in an asymmetric GaN quantum disc (Q-disc) system. Overall, good agreement between the modeling and experimental results were observed. Furthermore, modeling has provided an insight into the carrier dynamics of the Q-disc system. In particular, results from the modeling supports the view that the nonlinear relationship between PL intensity and excitation power was due to electron tunneling between the asymmetric GaN Q-discs. ©2005 IEEE.

Abstract:

We discuss a novel technique to register the spatial and spectral characteristics of a single quantum dot using two photon absorption laser lithography. This would be useful in realizing solid state cavity quantum electrodynamics. © 2005 British Crown Copyright.