No abstract

The photoluminescence emission peak energy of GaN quantum dots was observed to shift to higher energy with decreasing quantum dot size. This effect was found to be a combination of a blueshift from the confinement-induced shift of the electronic levels and a redshift from the increased Coulomb energy induced by a compression of the exciton Bohr radius. From this observation, absolute values of the exciton binding energy as a function of quantum dot size are determined.

We report on the unambiguous experimental determination of the photoluminescence mechanism in a set of In0.25Ga0.75N quantum wells. Instead of studying the photoluminescence for different In contents, we have investigated it as a function of the quantum well width in combination with a similar study performed on GaN quantum wells. In this way, we show that the photoluminescence is not coming from quantum dots or very localized states in the quantum well, but from the quantum well itself under the influence of a piezoelectric field induced by strain. The previously reported abnormal photoluminescence shifts and temperature dependencies can thus be explained.

Articles you may be interested inInfluence of the GaN barrier thickness on the optical properties of InGaN/GaN multilayer quantum dot heterostructures Appl. Phys. Lett. 96, 251904 (2010); 10.1063/1.3456392 Microstructural and optical properties of self-organized GaN quantum-dot assemblies

We report on an investigation of the coupling between excitons and longitudinal optical phonons as a function of GaN quantum dot size. Photoluminescence measurements of the quantum dots from cryogenic temperatures up to above room temperature are presented. The experiments were performed on ensembles of AlN capped GaN quantum dots grown on an Al0.15Ga0.85N surface by means of metalorganic vapor phase epitaxy. The results are analyzed on the basis of a Bose–Einstein-type expression describing the exciton to longitudinal optical phonon coupling of the dots as a function of the lattice temperature. A reduction of the exciton to LO-phonon coupling with decreasing quantum dot size was found.