High efficiency green, yellow, and amber emission from InGaN/GaN dot-in-a-wire heterostructures on Si (111) Appl. Phys. Lett. 96, 013106 (2010); 10.1063/1.3284660Exciton localization and quantum efficiency-A comparative cathodoluminescence study of (In,Ga)N/GaN and GaN/(Al,Ga)N quantum wells
Self-trapping of excitons is reported in AgCl nanocrystals embedded in a crystalline KCl matrix. The particles, observed by atomic force microscopy, have radii of several nanometers. Due to the spatial confinement only recombination of the self-trapped exciton ͑STE͒ is observed. STE(Br Ϫ ) and donor-acceptor pair recombination are absent. The time and temperature behavior of the emission is found to be significantly different from that in bulk AgCl. It is concluded that this is due to different self-trapped exciton configurations: The diffuse electron is spatially confined and centered in the nanocrystal whereas the compact hole, selftrapped at different lattice sites, causes variations in wave-function overlap in the different STEs. Optically detected magnetic resonance measurements reveal changes in g-values and a decrease by a factor of two in the magnitude of the zero-field splitting of the triplet state. They also demonstrate that the AgCl nanocrystal lattice axes are oriented along the axes of the KCl matrix.
The energetics and thermodynamic properties of cubic (c-)InxGa1−xN alloys are investigated by combining first-principles total energy calculations, a concentration-dependent cluster-based model, and Monte Carlo simulations. The search for the ground-state energies leads to the conclusion that biaxial strain suppresses phase separation, and acts as a driving force for chemical ordering in c-InxGa1−xN alloys. Ordered superlattice structures, with composition x≅0.5 and stable up to T=1000 K, arises as the relevant thermodynamic property of the strained alloy. We suggest that the In-rich phases recently observed by us in c-GaN/InxGa1−xN/GaN double heterostructures are ordered domains formed in the alloy layers due to biaxial strain.
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