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Huizhou, China

Wang H.,South China University of Technology | Zhou S.,South China University of Technology | Lin Z.,South China University of Technology | Hong X.,NVC Lighting | Li G.,South China University of Technology
Japanese Journal of Applied Physics | Year: 2013

This work has proposed a new way to optimize the spherical cap-shaped patterned sapphire substrate (PSS) for highly efficient GaN-based light emitting diodes (LEDs), which has been compared with the hemisphere patterned one. This pattern is achieved by changing the height of hemispherical units on the basis of hemispherical PSS. The height, the distance and the radius of the spherical cap-shaped unit are subsequently optimised by optical simulation. It is revealed that this optimised spherical cap-shaped PSS can enhance light extraction yield of LEDs by over 10% compared with LEDs grown on the optimal hemispherical PSS. The effectiveness of this spherical cap-shaped PSS has been demonstrated by subsequent crystal growth and characterization of LED wafers, and therefore sheds light on a further improvement on LED efficacy by the design of novel patterns for the application of PSS technology. © 2013 The Japan Society of Applied Physics. Source


Liu M.,South China University of Technology | Ling J.,South China University of Technology | Liu J.,South China University of Technology | Hong X.,NVC Lighting | Li G.,South China University of Technology
Bandaoti Guangdian/Semiconductor Optoelectronics | Year: 2014

The SiC reinforced Al composite (AlSiC) with high SiC volume fraction was prepared by combination of compression molding and vacuum pressure infiltration. Detailed analysis on microstructure and phase was carried out. The results show that the AlSiC composite fabricated by the above-mentioned methods is free of porosity, and the SiC particles are distributed uniformly and high interfacial bonding strength is achieved. Moreover, the interfacial reaction is well controlled so that some harm phases, especially Al4C3 fragility, are absent from interfacial reaction products. The mechanism behind the experimental phenomenon was analyzed in detail. It is indicated that the silicon addition in the 6061 aluminum alloy and process conditions of vacuum pressure infiltration can effectively prevent the formation of Al4C3 fragility phase. Thermal properties of the samples were also tested. The results indicate that the thermal expansion coefficient of aluminum silicon carbide increase first and then decrease with the increase of temperature, reaching the maximum at 315°C. The coefficient of thermal expansion of aluminum silicon carbide is 7.00×10-6°C-1, the thermal conductivity is 155.1 W/m·K, and the density is 3.1 g/cm3. The aluminum silicon carbide composite can fully meet high-end electronic packaging materials requirements. Source


Wang H.,South China University of Technology | Zhou S.,South China University of Technology | Lin Z.,South China University of Technology | Qiao T.,South China University of Technology | And 4 more authors.
RSC Advances | Year: 2014

This work has studied the influence of the generatrix's curvature of a dome-shaped patterned sapphire substrate (PSS) on the efficacy of GaN-based light emitting diodes (LEDs). The generatrix's central angle is carefully optimized by optical simulation. It is revealed that the dome-shaped PSS with a generatrix central angle of 10° is optimal to improve the luminous efficacy of LED devices. Subsequent crystal growth and characterization of LED wafers grown on dome-shaped PSSs with different generatrix central angles indicate that the central angle will not influence the as-grown LED wafers' crystalline quality, and the optimal central angle of 10° can enhance LED efficacy by about 19%. This journal is © the Partner Organisations 2014. Source


Zhou S.,South China University of Technology | Wang H.,South China University of Technology | Lin Z.,South China University of Technology | Yang H.,South China University of Technology | And 2 more authors.
Japanese Journal of Applied Physics | Year: 2014

In this work, we focus on the study of defects in GaN grown on an optimized hemispherical patterned sapphire substrate (PSS). It is demonstrated that the proposed patterns can on the one hand induce the formation of stacking faults, and on the other hand, reduce the strain caused by thermal misfit and lattice misfit. Consequently, the optimized hemispherical patterns work successfully for both the reduction in the number of dislocations spreading to multiple quantum wells and the improvement in surface morphology. The dominant mechanism of defect multiplication and the effects of optimized hemispherical patterns in terms of materials science and device technology are elucidated. © 2014 The Japan Society of Applied Physics. Source


Lin Z.,South China University of Technology | Yang H.,South China University of Technology | Zhou S.,South China University of Technology | Wang H.,South China University of Technology | And 2 more authors.
Crystal Growth and Design | Year: 2012

This work represents a cost and time effective approach for pattern design of patterned sapphire substrates (PSS) for highly efficient GaN-based light emitting diodes (LEDs). Simulation is used to study how external quantum efficiency changes with the change in parameters of the unit hemisphere for LEDs fabricated on hemispherical PSS. Through a series of comparisons on simulation results, the most effective pattern to improve external quantum efficiency of LEDs on hemispherical PSS is revealed. The subsequent crystal growth of LED wafers demonstrates that both photoluminescence and electroluminescence intensities dramatically increase by about a half for LEDs grown on this pattern-optimized PSS compared to that of LEDs on non-PSS, which straight-forwardly proves the high efficiency of the optimized hemispherical patterns of PSS for improving LED efficacy. © 2012 American Chemical Society. Source

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