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Scanning near-field photoluminescence spectroscopy has been applied to distinguish the relevance of quantum well (QW) alloy composition and well width fluctuations on emission linewidth and recombination times in semipolar (2021) plane InGaN QWs. It has been found that well width fluctuations, compared to variations of InGaN alloy composition, play a negligible role in defining the photoluminescence linewidth. However, the well width strongly affects the recombination times. Prolonged radiative and nonradiative carrier lifetimes in wide QWs have been attributed to electron and hole separation by in-plane electric fields caused by nonplanarity of QW interfaces., QC 20210216

Scanning near-field photoluminescence (PL) spectroscopy has been applied to green emitting (2021) plane InGaN/GaN quantum well (QW) structures with 1, 5 and 10 wells to reveal the influence of the number of QWS on PL properties and their spatial variation. The data show no additional broadening or shift of the PL spectra related to the increase of the number of QWs. The QWs in the multiple QW structures are found to be nearly identical and the well width and/or alloy composition fluctuations uncorrelated. In spite that the thickness of the 10 QW structure is over the critical, no PL changes related to a structural relaxation have been detected., QC 20160203. QC 20160304

Scanning near-field optical spectroscopy was applied to study spatial variations of emission spectra at room temperature in semipolar (20 (2) over bar1) InxGa(1-x)N/GaN single quantum wells (QWs) for 0:11 <= x <= 0:36. Photoluminescence (PL) was found to be highly uniform, with peak wavelength deviations and peak intensity deviations divided by average values in the range of 6-12 meV and 0.03-0.07, respectively. Near-field maps of PL parameters showed large, similar to 5 to 10 mu m size areas of similar values, as opposed to 100 nm scale variations, often reported for InGaN QWs. The near-field PL spectra were found to broaden with increasing InN molar fraction. In the low In content QWs, the broadening is primarily determined by the random cation distribution, while for larger InN molar fractions 10 nm scale localization sites with increasingly deeper band potentials are suggested as the linewidth broadening cause., QC 20150226

Semipolar (20 (2) over bar1) plane In,Ga1-xN quantum wells (QWs) of varying alloy composition were studied by time-resolved photoluminescence. A large difference in effective radiative lifetimes. from sub-ns for x = 0.11 to similar to 30 ns for x approximate to 0.35 was found. This effect is attributed to different properties of carrier localization. In low In content QWs. recombination at extended states with short recombination times is prevalent. In QWs with a high In content, the lifetimes are increased by localization of electrons and holes at separate sites. The zigzag shape of the QW interfaces and the resulting in-plane electric field are proposed as the cause for the separate electron and hole localization., QC 20160114