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The future generation of modern illumination should not only be cheap and highly efficient, but also demonstrate high quality of light, light which allows better color differentiation and fidelity. Here we are presenting a novel approach to create a white solid-state light source providing ultimate color rendition necessary for a number of applications. The proposed semi-hybrid device combines a monolithic blue-cyan light emitting diode (MBC LED) with a green-red phosphor mixture. It has shown a superior color rendering index (CRI), 98.6, at correlated color temperature of around 3400 K. The MBC LED epi-structure did not suffer from the efficiency reduction typical for monolithic multi-color emitters and was implemented in the two most popular chip designs: “epi-up” and “flip-chip”. Redistribution of the blue and cyan band amplitudes in the white-light emission spectrum, using the operating current, is found to be an effective tool for fine tuning the color characteristics. (Figure presented.).

We demonstrate a phosphor free, dichromatic GaN-based monolithic white LED with vertically stacked green and blue emitting multiple quantum wells. The optimal thickness of GaN barrier layer between green and blue quantum wells used is 8 nm. This device can be tuned over a wide range of correlated color temperature (CCT) to achieve warm white (CCT = 3600 K) to cool white (CCT = 13,000 K) emission by current modulation from 2.3 A/cm2 to 12.9 A/cm2. It is also demonstrated for the first time that a color rendering index (CRI) as high as 67 can be achieved with such a dichromatic source. The observed CCT and CRI tunability is associated with the spectral power evolution due to the pumping-induced carrier redistribution.

We demonstrate a resonant Bragg structure formed by quasi-two-dimensional excitons in periodic systems of InGaN quantum wells (QWs) separated by GaN barriers. When the Bragg resonance and exciton–polariton resonance are tuned to each other, the medium exhibits an exciton-mediated resonantly enhanced optical Bragg reflection. The enhancement factor appeared to be largest for the system of 60 QWs. Owing to a high binding energy and oscillator strength of the excitons in InGaN QWs, the resonant enhancement was achieved at room temperature. The samples were grown by the metal–organic vapor-phase epitaxy (MOVPE) on GaN-on-sapphire templates. The most important technological problem of the developed structures is inhomogeneous broadening of the excitonic states due to nonuniform chemical composition of the QWs driven by InN–GaN phase separation trend. We addressed this problem by variation of the vapor pressure, growth rate, growth interactions, and admixing of hydrogen during the MOVPE. The lowest width of 74 meV at room temperature and 41 meV at 77 K was achieved for the excitonic emission line from a single InGaN QW.

In this study we investigate the possibility of a-GaN ELOG process and its peculiarities for stripes of various orientations. It is shown that stripe orientation allows governing such important parameters of ELOG-process as lateral growth rate, voids high, fast growth direction. The intermediate orientations of stripe windows (differ from conventional (0001) and (1–100)) can be effectively used for double-cross ELOG process. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In this paper we obtained GaN and InGaN nanowires on AlN/Si (111) templates via pulsed Metal Organic Chemical Vapour Deposition (MOCVD). The growth modes were investigated, in which selective growth is possible. The impact of NH3 flow and TMG flow and exposure time were investigated. Also the possibility of using indium catalyst was studied. It was shown that In can be used in Au-In melt and as self-suffisient catalyst. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Internal Quantum Efficiency (IQE) of two-colour monolithic white light emitting diode (LED) was measured by temperature dependant electro-luminescence (TDEL) and analysed with modified rate equation based on ABC model. External, internal and injection efficiencies of blue and green quantum wells were analysed separately. Monolithic white LED contained one green InGaN QW and two blue QWs being separated by GaN barrier. This paper reports also the tunable behaviour of correlated colour temperature (CCT) in pulsed operation mode and effect of self-heating on device performance.