We compare the optical properties of GaN/Al0.15Ga0.85N multiple quantum wells grown on an m-plane (10-10) oriented GaN substrate with those of (1-101)-oriented GaN/Al0.15Ga0.85N multiple quantum wells grown by metal-organic chemical vapor deposition on a patterned (001) 7°-off oriented silicon substrate. The optical properties are studied in 8K-300K temperature range. They reveal strong in-plane optical anisotropies as predicted by group theory. Polarized time resolved temperature- dependent photoluminescence experiments are performed providing access to the relative contributions of the non-radiative and radiative recombination processes. We deduce the variation of the radiative decay time with temperature in the two polarizations. A global comparison of the light emission efficiency in both samples is finally addressed and brought in agreement with the predictions of k.p calculations.

The group III wurtzite nitrides have been revolutionizing the physics of semiconductors for more than two decades after that high quality materials could be grown and silicon n-type and magnesium p-type were realized at the end of the eighties. Based on this, candela class blue light emitting diodes and blue lasers were realized and commercialized. These triggered solid-state lighting and Blu-Ray DVD technology. Besides this massive arrival of optical devices on the market, a lot of basic physics phenomena inherent to the wurtzite symmetry were discovered or clarified, at least quantitatively framed. This was, and still is, of paramount importance for improving the performances of the nitride-based devices. I will review the different steps that paved the way of this breakthroughs and I will discuss the important issues that still have to be overcome in the next years: filling the green gap and realizing high luminosity amber or red light-emitting diodes in the one hand, designing and growing ultra violet light emitters in the other hand. The drawbacks inherent to the materials such as Auger non-radiative recombination processes will be discussed as well as the potentialities of growth on high Miller index surfaces for bypassing the deleterious Quantum Confined Stark Effect, for reducing the dislocation densities and for improving the performances of the generations of devices in the next years. The Nano-LEDs based on one-dimensional nitride crystals will be discussed as well as Nano lasers. Then, I will show results obtained regarding nitride quantum dots and single photon emitters, which are now grown on a large variety of surfaces, sometimes embedded into micro-cavities. At the end I will dedicate a few minutes to the presentation of boron nitride, a layered compound. Its physics is becoming a hot topics and one of the pioneers of the growth of nitrides speaks of it in terms of " the next guy".

We report an unusual temperature dependence of exciton lifetimes in arrays of GaN nanostructures grown onsemipolar (11-22) oriented Al0.5Ga0.5Nalloy by molecular beam epitaxy.Atomic force microscopy measurementsrevealed: (i) a one-dimensional ordering tendency along the [1-100] crystallographic direction together with (ii)an in-plane anisotropy of the nanostructure lateral shape with respect to [1-100] and [11-23] crystallographicaxes. As a consequence, a morphological transition from dot-shaped islands forming an array of nanochains towire-shaped objects elongated along the [1-100] direction was evidenced with the increase of the GaN depositedamount. Nanostructures of different dimensionality were fabricated including quantum dots (QDs), quantumwires (QWRs), and quantum wells (QWs), and the excitonic behavior was investigated as a function of thenanostructure shape. The measured temperature dependencies of the exciton radiative decay revealed its directcorrelation with a spatial confinement, resulting in a temperature-independent exciton lifetime in the case ofQDs, a square root dependence in the case of QWRs, and a linear dependence for QWs. These results, as well asabsolute values of measured lifetimes, are in agreement with theoretical predictions.

The optical properties of GaN/Al0.15Ga0.85N multiple quantum wells are examined in 8K–300K temperature range. Both polarized CW and time resolved temperature-dependent photoluminescence experiment are performed so that we can deduce the relative contributions of the non-radiative and radiative recombination processes. From the calculation of the proportion of the excitonic population having wave vector in the light cone, we can deduce the variation of the radiative decay time with temperature. We find part of the excitonic population to be localized in concert with the report of Corfdir et al. (Jpn. J. Appl. Phys., Part 2 52, 08JC01 (2013)) in case of a-plane quantum wells. VC 2014 AIP Publishing LLC.

AlGaN-based ultra-violet (UV) light emitting diodes (LEDs) are seen as the best solution for the replacement of traditional mercury lamp technology. By adjusting the Al concentration, a large emission spectrum range from 360 nm (GaN) down to 200 nm (AlN) can be covered. Owing to the large density of defects typically present in AlGaN materials usually grown on sapphire substrates, LED efficiencies still need to be improved. Taking advantage of the 3D carrier confinement, quantum dots (QDs) are among the solutions currently under investigation to improve the performances of UV LEDs. The objectives of this work are to present and discuss the morphological and optical properties of GaN nanostructures grown by molecular beam epitaxy on the (0 0 0 1) and the (11-22) orientations of Al0.5Ga0.5N. In particular, the dependence of the morphological properties of the nanostructures on the growth conditions and the surface orientation will be presented. The optical characteristics as a function of the nanostructure design (size, shape and dimensionality) will also be shown and discussed. The electroluminescence characteristics of a first series of QD-based GaNAl0.5Ga0.5N LEDs grown on the polar (0 0 0 1) plane will be investigated

The optical properties of GaN/Al0.15Ga0.85N multiple quantum wells grown on m-plane oriented substrate are studied in 8K–300K temperature range. The optical spectra reveal strong in-plane optical anisotropies as predicted by group theory. Polarized time resolved temperature-dependent photoluminescence experiments are performed providing access to the relative contributions of the non-radiative and radiative recombination processes. We deduce the variation of the radiative decay time with temperature in the two polarizations. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.