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Liu T.,Harbin Institute of Technology | Jiao S.,Harbin Institute of Technology | Jiao S.,Harbin Normal University | Liang H.,Dalian University of Technology | And 3 more authors.
RSC Advances | Year: 2015

The structural and optical properties of near-ultraviolet (UV) multiple quantum well (MQW) structures using quaternary AlInGaN as the well layers have been investigated. The composition of the barrier layers is determined by three In0.08Ga0.92N/AlxInyGa1-x-yN multiple quantum well samples with varying Al content in the barrier layers. The compositions of the well and barrier layers are estimated from the high-resolution X-ray diffraction (HRXRD) results. In spite of the larger lattice mismatch, the remarkable enhancement of the photoluminescence (PL) intensity of the MQWs sample with AlInGaN as the well layers is attributed to the increase in the carrier localized states induced by the increase in the compositional fluctuation in the AlInGaN well layers. The S-shaped temperature-dependence of the PL peak energy indicates the existence of localized states induced by the potential fluctuations. The magnitude of the carrier localization, which is estimated by the fitting results, is significantly increased in the Al0.11In0.13Ga0.76N/Al0.16In0.045Ga0.795N MQWs due to the improvement of the spatial potential fluctuations using quaternary AlInGaN as the well layers. © The Royal Society of Chemistry 2015.

Liu T.,Harbin Institute of Technology | Jiao S.,Harbin Institute of Technology | Jiao S.,Harbin Normal University | Jiao S.,CAS Suzhou Institute of Nano Technology and Nano Bionics | And 5 more authors.
Journal of Alloys and Compounds | Year: 2015

The structural and optical properties of In0.20Ga0.80N/AlxInyGa1-x-yN multiple quantum wells samples with varying Al content in barrier layers grown on sapphire substrates by metalorganic chemical vapor deposition have been investigated by means of high-resolution X-ray diffraction, Raman scattering measurements and temperature-dependent photoluminescence. Raman measurements verified the existence of In-rich clusters in ternary and quaternary layers. At 10 K and 300 K, the PL spectrum of each sample is dominated by a sharp emission peak arising from In0.20Ga0.80N well layers. The anomalous temperature-dependent S-shaped behaviors of emission energies have been observed, indicating the presence of localized states induced by the potential fluctuations in the quantum wells due to the inhomogeneous distribution of In-rich clusters. The degree of the localization effect and the transition temperatures between different temperature regions can be enhanced by increasing Al content in barrier layers. The improvement of the localized states emission has been observed at the lower energy side of band gap emission of quantum wells with increasing Al content. The origin of the deep localized states could be attributed to the larger quantum-confined Stark effect in the quantum wells with higher Al content. The recombination mechanism of carriers between band edge and localized states was proposed for interpreting of the emission characteristics. © 2014 Elsevier B.V. All rights reserved.

Xu J.,Nanjing Southeast University | Zhang X.,Nanjing Southeast University | Yang H.,Nanjing Southeast University | Guo H.,Nanjing Southeast University | And 3 more authors.
Japanese Journal of Applied Physics | Year: 2014

Si-doped n-InGaN/GaN composite current-spreading layers (CCSLs) inserted between the n-GaN layer and the InGaN/GaN multiple-quantumwell (MQW) active region were developed and optimized for the GaN-based light-emitting diodes (LEDs). It was found that with the optimized n- InGaN/GaN CCSLs lightly doped with Si, the crystalline quality as well as the electric and optical properties of the GaN-based LEDs, such as forward voltage Vf, photoluminescence (PL) intensity, and electrostatic discharge (ESD) endurance could be significantly improved. In particular, an ESD pass yield as high as 99.49% at a 2000V reverse bias has been achieved for the GaN-based LEDs with the 70nm/70nm n-InGaN/GaN CCSLs. This means that the n-InGaN/GaN CCSLs with carefully optimized layer thickness could play a key role in improving the crystalline quality and enhancing the device performance of the GaN-based LEDs. © 2014 The Japan Society of Applied Physics.

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