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Via temperature-dependent time-resolved photoluminescence spectroscopy, we investigate the radiative and nonradiative recombination processes in thin (quantum well widths of about 1.5 nm) a-plane, m-plane, () and () GaInN/GaN fivefold quantum well structures of varying indium content grown on low defect density GaN substrates and GaN templates. At room temperature, we observe surprisingly short radiative lifetimes in the range from 100 ps to 1 ns for these structures, being about one to two orders of magnitude shorter than for similar c-plane quantum wells. This large difference cannot solely be explained by the larger overlap matrix element in non- and semipolar wells. Higher exciton binding energies and lower effective density of states masses may contribute to an enhanced radiative probability. The nonradiative recombination exhibits a thermally activated behavior with activation energies of about 10 meV for () and around 25 meV for nonpolar quantum wells. These values are lower than the quantum well barrier height and the exciton binding energy, but in a similar range as the localization energies estimated from the radiative recombination.

In recent years, a wide range of generalized barycentric coordinates has been suggested. However, all of them lack control over derivatives. We show how the notion of barycentric coordinates can be extended to specify derivatives at control points. This is also known as Hermite interpolation. We introduce a method to modify existing barycentric coordinates to higher order barycentric coordinates and demonstrate, using higher order mean value coordinates, that our method, although conceptually simple and easy to implement, can be used to give easy and intuitive control at interactive frame rates over local space deformations such as rotations.

Using time-resolved photoluminescence spectroscopy on GaInN/GaN multiple quantum well structures, we analyze the radiative and nonradiative processes contributing to the “green gap” in GaN-based light emitting devices. We observe that it is only partly caused by a reduced oscillator strength due to the Quantum Confined Stark Effect (QCSE) which becomes stronger with increasing indium concentration and well width. As the dominant effect we observe a reduction of nonradiative lifetimes when the indium concentration is increased. For higher indium concentrations, we find an additional nonradiative recombination path that might be attributed to an increased generation of defects like misfit dislocations, nitrogen vacancies and/or indium clusters within the optically active region. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)