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Title: Characterization of GaN/InGaN multiple quantum wells grown on sapphire substrates by nano-scale epitaxial lateral overgrowth technique
Authors: Fong, WK
Leung, KK
Surya, C 
Keywords: A1. Multiple quantum wells
A1. Optical properties
A3. Epitaxial lateral overgrowth
B1. GaN
Issue Date: 2011
Publisher: North-Holland
Source: Journal of crystal growth, 2011, v. 318, no. 1, p. 488-491 How to cite?
Journal: Journal of crystal growth 
Abstract: High-quality GaN/InGaN multiple quantum wells (MQWs) were fabricated on nano-scale epitaxial lateral overgrown (NELO) GaN layers. To grow the NELO layer first a 200 nm-thick SiO 2 was deposited on a 2 μm-thick undoped GaN layer. A 10 nm-thick Ni layer was then deposited on the SiO 2 film followed by an annealing process to form nano-scale Ni clusters. These Ni clusters will serve as a dry etch mask for the underlying SiO 2 layer, resulting in the formation of SiO 2 islands of diameter and inter-distance of 300 and 200 nm, respectively. Undoped NELO GaN layer of thickness 2 μm was grown on the template with SiO 2 growth mask using metal organic chemical vapor deposition technique. A 2 μm-thick n-GaN epilayer and a 5-period GaN/InGaN MQWs were grown on top of the NELO layer. It is found that the overgrown GaN epilayers exhibit a significant reduction in threading dislocation (TD). From the atomic force microscopy characterizations, the TD density reduces from 3×10 8 to 6×10 7 cm -2 by utilizing the NELO technique. Optical properties of the MQWs deposited on the NELO layer (type N) were characterized by temperature-dependent photoluminescence (PL). The results are compared to a control structure (type C) grown in the same growth run as the type N structures but without the NELO layer. It is found that type N sample exhibits three-fold improvement in PL intensity at room temperature. The increase in external quantum efficiency arises from both enhanced extraction efficiency and internal quantum efficiency. Detailed temperature-dependent PL studies were conducted to evaluate the relative improvement in internal quantum efficiency to account for the improved material quality when MQWs were grown on top of NELO epilayers.
ISSN: 0022-0248
DOI: 10.1016/j.jcrysgro.2010.10.048
Appears in Collections:Conference Paper

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