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Tsai P.Y.,National Cheng Kung University | Huang H.K.,National Cheng Kung University | Sung C.-M.,Ritedia | Kan M.C.,Ritedia | Wang Y.H.,National Cheng Kung University
IEEE Electron Device Letters | Year: 2013

Vertical light-emitting diodes (VLEDs) with diamondlike carbon/titanium (DLC/Ti) heat-spreading layers on silicon (Si) substrates are investigated. Good thermal conductivity coupled with a thermal expansion coefficient similar to that of gallium nitride enables DLC/Ti to enhance heat dissipation via the Si substrate for Si-bonded VLEDs. The relative light intensity of VLEDs with DLC/Ti operating at 1 A is 10% greater than that of VLEDs without DLC/Ti. The output power droop can be further improved. A slight red shift of 0.5 nm occurs when the injection current is increased from 0.7 to 1 A. VLEDs with DLC/Ti also have lower and more uniform surface temperatures than VLEDs without DLC/Ti. The measured thermal resistance of VLEDs with and without DLC/Ti is 0.63 and 1.51 K/W at an injection current of 350 mA, respectively. This observation shows that the proposed DLC/Ti heat-spreading layer facilitates efficient thermal management in VLEDs. © 1980-2012 IEEE. Source


Tsai P.-Y.,National Cheng Kung University | Huang H.-K.,National Cheng Kung University | Sung C.-M.,Ritedia | Kan M.-C.,Ritedia | Wang Y.-H.,National Cheng Kung University
International Journal of Photoenergy | Year: 2014

The temperature-dependent optical, electrical, and thermal properties of flip-chip light emitting diodes (FCLEDs) with diamond-like carbon (DLC) heat-spreading layers were investigated. On the basis of the measured results in the 20°C to 100°C temperature range, a significant performance improvement can be achieved for FCLEDs with DLC heat-spreading layers (DLC-FCLED) compared with FCLEDs without DLC heat-spreading layers (non-DLC-FCLED). The external quantum efficiency (EQE) of the DLC-FCLED improves by 9% at an injection current of 1000 mA and a temperature of 100°C. The forward voltage and spectra variations are smaller than those of non-DLC-FCLEDs. The DLC-FCLED provides high efficiency and high stability performance for high-power and high-temperature applications. © 2014 Pai-Yang Tsai et al. Source


Tsai P.-Y.,National Cheng Kung University | Huang H.-K.,National Cheng Kung University | Sung J.-M.,Ritedia | Kan M.-C.,Ritedia | Wang Y.-H.,National Cheng Kung University
IEEE Electron Device Letters | Year: 2015

High thermal stability and wide angle of a white light chip-on-board package using a remote phosphor structure was investigated. The junction and phosphor layer temperatures of the remote phosphor structure are lower than those of the conventional phosphor structure. Compared with the conventional structure, the luminous flux and luminous efficiency of the proposed phosphor structure are improved by more than 10% at an injection current of 1 A in the continuous wave mode. For the color temperature shift, the remote phosphor structure is more stable than the conventional one. In the radiation pattern, the remote phosphor structure is improved over 40°. Consequently, the remote phosphor structure is more suitable than the conventional phosphor structure in thermal stability and wide-angle lighting application. © 1980-2012 IEEE. Source

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