Smith micro amberlight4/16/2023 ![]() Based on a large set of QWs grown on different crystal orientations, we correlated the wavelength and the luminescence FWHM of InGaN/GaN QWs to build a model which predicts the perceived chromaticity, i.e., the apparent hue and saturation of yellow-red nitride LEDs. ![]() As a consequence, for red InGaN QW based LEDs, the peak wavelength must be even further in the red. This phenomenon is known as Abney effect, and it originates from the spectral sensitivities of the cone cells of the human eyes. More important, in the yellow-red range, the perceived hue is strongly blue-shifted by a broad emission. For emission wavelengths longer than 515 nm, the saturation surprisingly increases again and reaches 95% beyond 560 nm. This broadening of the luminescence decreases the color saturation from 100% to about 70% up a wavelength shorter than 515 nm. The full width at half maximum (FWHM) of the luminescence of visible InGaN quantum well (QW) based emitters increases with wavelength. Despite these defects, the PL is highly improved toward the red wavelengths and compares with the reports on ultrathin AlGaN layers where this has been correlated with the improvement of the crystalline quality, although with less strain compensation. These domains systematically contribute to a local decrease of the QW thickness and most probably to an efficient localization of carriers. It is found that the crystalline quality of the system is progressively degraded when the thickness of the AlGaN interlayer is increased through strain concentrated domains, which randomly form inside the 3 nm GaN low temperature layer. In this instance, AlGaN was grown at the same temperature as the GaN barrier, on top of a protective 3 nm GaN. The compensation is full from an AlGaN layer thickness of 5.2 nm, and this does not change up to the largest one that has been investigated. For different AlGaN strain compensating layer thicknesses varying from 0 to 10.6 nm, a detailed x-ray diffraction analysis shows that the MQW stack becomes completely strained on GaN along a and c. In this work, InGaN/GaN multi-quantum Wells (MQWs) with strain compensating AlGaN interlayers grown by metalorganic vapor-phase epitaxy have been investigated by high-resolution x-ray diffraction, transmission electron microscopy, and photoluminescence (PL). In addition, we find that intercalating an AlGaN-strain-compensating layer reduces not only the coefficient of nonradiative recombination rates but also reduces the onset of Auger recombination. We find that the Auger effect dominates in the high-excitation regime. After extracting the evolution of IQE with pump power from the experimental data, we use a modified ABC modeling that includes the residual n-type doping to estimate the contribution of different recombination channels. Above this threshold, the variation of the intensity becomes sublinear, which is characteristic of the onset of Auger recombination processes. T that depends on the design of the sample. Photoluminescence intensity recorded as a function of excitation power density follows a linear dependence up to a threshold P The Auger effect and its impact on the internal quantum efficiency (IQE) of yellow light emitters based on silicon-doped InGaN–AlGaN–GaN quantum wells are investigated by power dependence measurement and using an ABC model. The increase in the value of coefficient C with changing temperature reveals indirect Auger recombination that relates to the interactions of the carriers with other phonons than the longitudinal optical one. At low temperature, both quantum confined Stark effect and carrier localization trigger electron-electron repulsions and therefore the onset of the Auger effect. The temperature dependences of the different recombination mechanisms are determined. In such high excitation conditions with efficient Auger recombination, the variation of the IQE with the photo-excitation density P is ruled by a universal power law independent of the design: IQE = IQEMAX – a log10P with a close to 1/3. ![]() Strong quantum confined Stark effect and carrier localization induce an increase in the carrier density and then favor Auger non-radiative recombination in the high excitation range. By changing the well width, the indium content, and adding a strain compensation AlGaN layer, we could tune the intrinsic radiative recombination rate by changing the quantum confined Stark effect, and we could modify the carrier localization. The variation of the internal quantum efficiency (IQE) of single InGaN quantum well structures emitting from blue to red is studied as a function of the excitation power density and the temperature.
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