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Despite an already existing abundant literature dedicated to report of lot of experimental investigations towards the understanting of the mechanisms that rule the limitation of intense light emission in nitride-based heterostructures, there are still some issues that are not fully elucidated. This is probably related to the lack of investigations away from the blue and aquamarine light regions. In this communication we cover the 480 nm to 620 nm range by using a series of samples with different designs: single and multiple GaInN-GaN quantum wells. This paper is limited to heterostructures grown along the polar orientation. By changing the well width, and the indium content we could tune in the one hand the Quantum Confined Stark Effect that is to say the intrinsic radiative recombination rate while we could tune the crystalline quality by using strain-compensated GaInN-GaN-AlGaN designs. Finally, by changing our optical pump density we modified the intrinsic non radiative Auger. Given an emission wavelength, we find that the photoexcitation density P for the onset of substantial Auger effect to increase with the number of wells. Using an ABC-type modelling we find a clear 3/2 power law correlation between parameters B and C. This behavior is discussed in terms of electron-hole coulomb interaction and electron-electron repulsion in photo-excited samples. In condition of efficient Auger recombination, the variation of the internal quantum efficiency with photoexcitation density is ruled by a universal power law independent of the design: IQE = IQE0 – a log10 P with a =16 %cm2/Watt.

GaN-Al0.5NGa0.5N quantum dots deposited on (11-22) planes have been grown by combining Molecular Beam Epitaxy and Metal Organic Vapour Phase Epitaxy. This combination is interesting for realization of ultraviolet operation light emitting diodes, lasers andsingle photon sources,… (1,3) The growth of dots was achieved by MBE using ammonia as nitrogen precursor and growth interruption in ammonia less conditions to trigger corrugation of GaN and dot formation (4). The (11-22) GaN oriented peudosubstrate was realized by MOVPE starting from a M-plane oriented sapphire substrate. The orientation of the growth plane dictates in-plane anisotropies which are effectively found leading to a transition from isolated dots to nanochains - oriented along the direction as evidenced from Atomic Force Microscopy features or optical properties: polarization rates and temperature dependent measurements of the radiative recombination process for instance(5). We here restrict to small size isolated quantum dots and present innovative optical properties among which are micro-photoluminescence data versus pump power, polarization of the emitted photons at different temperatures. We also analyse the photoluminescence decay times and model our finding in the context of the effective mass approximation. The crystal field splitting is measured in Al 0.5NGa 0.5N lattice-matched to (11-2) oriented GaN by polarized microphotoluminecence under high photo- injection conditions.

Commercially available inorganic white light emitting diodes (LEDs) are essentially based on the combination of a blue InGaN based LED chip covered by a long wavelength emitting (yellow, red) phosphor. We propose to avoid this step of phosphor deposition by taking advantage of the fact that yellow to red emission can be achieved using InGaN alloys. By stacking an InGaN/GaN multiple quantum well (QW) emitting in the yellow, acting as a light converter, and a short wavelength blue-violet pump LED grown on top, white light emission can be obtained. Furthermore, if we extend the emission spectrum of the light converter into the red, a warm white light color is demonstrated when a pump LED is grown on top. However, the high In content InGaN QWs of the light converter have a low thermal stability and the QW efficiency tends to degrade during the growth of the pump LED. Three different solutions are explored to avoid the thermal degradation of the light converter. The monolithic LED structures were grown by molecular beam epitaxy (MBE), by a combination of both MBE and metal-organic chemical vapor phase epitaxy (MOCVD), or by a low temperature full-MOCVD process. The best results are obtained using a complete MOCVD growth process. The structure and the MOCVD growth conditions are specifically adapted in order to avoid the thermal degradation of the large In composition InGaN QWs emitting at long wavelength during the growth of the subsequent layers.