Professor Robert Taylor

Abstract:

The Temperature dependence of the exciton radiative decay time in ZnO nanorods has been investigated, which is associated with the density of states for the intra-relaxation of thermally excited excitons. The photoluminescence decay time was calibrated by using the photoluminescence intensity in order to obtain the radiative decay time. In the absence of an external magnetic field, we have confirmed that the radiative decay time increased with temperature in a similar manner to that seen in bulk material (∼ T1.5). Under an external magnetic field of 6 T parallel to the c-axis, we found that the power coefficient of the radiative decay time with temperature decreased (∼ T1.3) when compared to that in the absence of a magnetic field. This result can be attributed to an enhancement of the effective mass perpendicular to the magnetic field and a redshift of the center-of-mass exciton as a consequence of perturbation effects in the weak-field regime.

Abstract:

We report on optical studies of non-polar InGaN quantum dots grown on the (11$ \bar 2 $2) plane. Excitonic and biexcitonic complexes are identified by their power dependence and show similar binding energies (∼ 36 meV) and recombination dynamics to conventional polar (0001) InGaN quantum dots. Measured lifetimes as low as 300 ps suggest a reduced internal electric field when compared with polar InGaN quantum dots. Temperature dependent micro-photoluminescence measurements on a single exciton with a lifetime of 327ps reveal no significant exciton linewidth broadening up to 120K, suggesting a reduction in phonon coupling strength when compared to polar quantum dots. This is supported by a measured lifetime of 313 ps for this exciton at 77 K, suggesting the measured exciton decay is almost purely radiative. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.