Direct generation of linearly polarized single photons with a deterministic axis in quantum dots

We report the direct generation of linearly polarized single photons with a deterministic polarization axis in self-assembled quantum dots (QDs), achieved by the use of non-polar InGaN without complex device geometry engineering. Here, we present a comprehensive investigation of the polarization properties of these QDs and their origin with statistically significant experimental data and rigorous k·p modeling. The experimental study of 180 individual QDs allows us to compute an average polarization degree of 0.90, with a standard deviation of only 0.08. When coupled with theoretical insights, we show that these QDs are highly insensitive to size differences, shape anisotropies, and material content variations. Furthermore, 91% of the studied QDs exhibit a polarization axis along the crystal [1–100] axis, with the other 9% polarized orthogonal to this direction. These features give non-polar InGaN QDs unique advantages in polarization control over other materials, such as conventional polar nitride, InAs, or CdSe QDs. Hence, the ability to generate single photons with polarization control makes non-polar InGaN QDs highly attractive for quantum cryptography protocols

The effect of dislocation density and surface morphology on the optical properties of InGaN/GaN quantum wells grown on r-plane sapphire substrates

The optical properties of non-polar InGaN/GaN multiple quantum wells grown on r-plane sapphire substrates are investigated as a function of threading dislocation density. The 6 K emission spectrum consists of a peak at 3.25 eV and a broad band centred around 2.64 eV. From microscopy and cathodoluminescence studies, the higher energy peak is assigned to recombination within quantum wells lying on the (1120) plane which are intersected by basal-plane stacking faults. The lower energy band is attributed to emission from sidewall quantum wells of varying width and composition which form on the various semi-polar facets of structural defects that develop during the quantum well growth. </jats:p

Electroluminescence studies of modulation p-doped quantum dot laser structures

Electroluminescence (EL) measurements have been performed on InAs/InGaAs/GaAs quantum dot (QD) structures with varying amounts of modulation p-doping. Temperature-dependent EL measurements show a reduction of the integrated EL intensity (IEL) with increasing temperature but with the size of this reduction decreasing with increasing doping level. An increase in the activation energy controlling the EL quenching is found with increasing p-doping. This is attributed to an increased coulombic attraction between the extrinsic holes and injected electrons. At room temperature and low injection current, a superlinear dependence of the IEL on the injection current is observed. This superlinearity decreases as the p-doping increases and this behavior indicates a reduction in the amount of nonradiative recombination. This reduction is believed to be caused by the saturation of nonradiative centers and/or reduced escape of electrons to the GaAs barrier due to the increased confinement potential

Direct generation of linearly polarized single photons with a deterministic axis in quantum dots

We report the direct generation of linearly polarized single photons with a deterministic polarization axis in self-assembled quantum dots (QDs), achieved by the use of non-polar InGaN without complex device geometry engineering. Here, we present a comprehensive investigation of the polarization properties of these QDs and their origin with statistically significant experimental data and rigorous k·p modeling. The experimental study of 180 individual QDs allows us to compute an average polarization degree of 0.90, with a standard deviation of only 0.08. When coupled with theoretical insights, we show that these QDs are highly insensitive to size differences, shape anisotropies, and material content variations. Furthermore, 91% of the studied QDs exhibit a polarization axis along the crystal [1–100] axis, with the other 9% polarized orthogonal to this direction. These features give non-polar InGaN QDs unique advantages in polarization control over other materials, such as conventional polar nitride, InAs, or CdSe QDs. Hence, the ability to generate single photons with polarization control makes non-polar InGaN QDs highly attractive for quantum cryptography protocols

Dataset for the figures in "Self-assembled Multilayers of Silica Nanospheres for Defect Reduction in Non- and Semipolar Gallium Nitride Epitaxial Layers"

These are supporting research data files for "Self-assembled Multilayers of Silica Nanospheres for Defect Reduction in Non- and Semipolar Gallium Nitride Epitaxial Layers" article, published in "Crystal Growth & Design": DOI: 10.1021/acs.cgd.5b01560. Detailed description of these data is contained within figure captions in paper (article's DOI will be available after publication).This record supports publication and is available at http://pubs.acs.org/doi/10.1021/acs.cgd.5b01560This work was supported by the EPSRC [grant numbers EP/J003603/1 and EP/M011682/1], by the European Research Council under the European Community’s Seventh Framework Programme [grant number FP7/2007-2013] and by ERC grants [grant number 279361 (MACONS) and grant number 280078 (EMATTER)]