Light-emitting diodes are becoming the alternative for future general lighting applications, with huge energy savings compared to conventional light sources owing to their high efficiency and reliability. Polarized light sources would largely enhance the efficiency in a number of applications, such as in liquid-crystal displays, and also greatly improve contrast in general illumination due to the reduction in indirect glare. Here, we demonstrate light-emitting diodes presenting high-brightness polarized light emission by combining the polarization-preserving and directional extraction properties of embedded photonic-crystals applied to non-polar gallium nitride. A directional enhancement of up to 1.8-fold was observed in the total polarized light emission together with a high polarization degree of 88.7% at 465 nm. We discuss the mechanisms of polarized light emission in non-polar gallium nitride and the photonic-crystal design rules to further increase the light-emitting diode brightness. This work could open the way to polarized white-light emitters through their association with polarization-preserving down-converting phosphors.

We demonstrate high performance InGaN/GaN multiple quantum well solar cells with thin quantum barriers and spectral response extending to 460 nm. Devices grown on bulk (0001) GaN substrates with up to 50 quantum wells (QWs) outperform those grown simultaneously on sapphire due to the lower threading dislocation density. Increasing the number of QWs eventually leads to performance degradation of devices grown on both substrates. Solar cells are demonstrated with peak external quantum efficiencies up to 60%, open circuit voltages up to 2.28 V, fill factors up to 80%, and conversion efficiencies up to 2.4% under 1 sun AM0 equivalent illumination.

Light-emitting diodes (LEDs) were fabricated in gallium nitride with two embedded photonic crystals (PhCs), creating a waveguide with a highly confined, strongly excited, and well-extracted fundamental mode. This structure improves upon previous PhC LED designs by reducing the extraction length of the fundamental mode and establishing a path to designs with very low absorption losses. Optical output was measured with angular-resolved electroluminescence. The extraction length of the fundamental mode was measured to be 21–39 μm along the PhCs’ Γ-M directions, which is much shorter than values reported for single-PhC devices. This structure opens the way to more efficient LEDs and lasers.

A two-step GaN barrier growth methodology was developed for In_xGa_1−xN/GaN multiple quantum well solar cells in which a lower temperature GaN cap layer was grown on top of the quantum wells (QWs) and then followed by a higher temperature GaN barrier layer. The performance of the solar cells improved markedly by increasing the low temperature GaN cap layer thickness from 1.5 to 3.0 nm. High-angle annular dark field scanning transmission electron microscopy and atom probe tomography measurements showed that increasing the GaN cap layer thickness improved the uniformity and increased the average indium content of the QWs.