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

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We have performed annealing experiments with c-InGaN/GaN double heterostructures in order to obtain information on the thermal stability and the formation process of In-rich clusters in the InGaN layers. While the as grown samples showed a dominating luminescence at about 2.3 eV, the annealed samples showed a new luminescence peak at 2.8-3.0 eV which may be due to a band gap emission of a regenerated layer with an In-content of about x ¼ 0.20. These results are corroborated by micro Raman spectroscopy. Our annealing experiments show that at elevated temperatures In-atoms can diffuse in c-InGaN layers while In-rich aggregates are stable at growth temperature.Introduction Recent X-ray diffraction and micro-Raman measurements gave first evidence of In-rich inclusions in c-InGaN layers [1]. Resonant Raman measurements show that the PL of these layers is related to In-rich nanometer-size quantum-dot (QD) like structures [2]. Investigations of the structure and photoluminescence (PL) from c-InGaN/GaN double heterostructures (DHs) showed the importance of the QD-like In-rich structures for the radiative recombination of electron hole pairs [3]. Evidence for radiative recombination of excitons localized in nanostructures such as In-rich clusters in cubic InGaN multiple quantum wells (MQWs) has also been reported in Ref. [4].In this paper we report on annealing experiments which were performed in order to obtain further insight into the formation process and the thermal stability of the In-rich clusters in our c-InGaN/GaN DHs.

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PACS: 78.55.Cr; 78.60.Hk; 81.15.Hi Cubic phase group III-nitrides were grown using RF plasma assisted Molecular Beam Epitaxy on GaAs (001) substrates. High-resolution X-ray diffraction, photoluminescence, cathodoluminescence and photoreflectance measurements were employed to characterize the structural and optical properties of GaN/Al x Ga 1--x N Multi Quantum Well (MQW) structures, in which both Aluminum content and well widths were varied. The observed quantized states are in agreement with first-principles based theoretical calculations.