Browsing by Author "Guo, Yih-Der"

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Reduction of Efficiency Droop in InGaN Light-Emitting Diode Grown on Self-Separated Freestanding GaN Substrates
(2011-06-15)
Chao, Chu-Li
;
Xuan, Rong
;
Yen, Hsi-Hsuan
;
Chiu, Ching-Hsueh
;
Fang, Yen-Hsiang
Using a GaN nanorod template in a hydride vapor phase epitaxy (HVPE) system can manufacture a freestanding GaN (FS-GaN) substrate with threading dislocation densities down to similar to 10(7) cm(-2). In this letter, we report InGaN/GaN multiple-quantum-well light-emitting diodes (LEDs) grown on this FS-GaN substrate. The defect densities in the homoepitaxially grown LEDs were substantially reduced, leading to improved light emission efficiency. Compared with the LED grown on sapphire, we obtained a lower forward voltage, smaller diode ideality factor, and higher light-output power in the same structure grown on FS-GaN. The external quantum efficiency (EQE) of LEDs grown on FS-GaN were improved especially at high injection current, which brought the efficiency droop phenomenon greatly reduced at high current density.
Self-separated freestanding GaN grown on patterned substrate by hydride vapor phase epitaxy
(2007)
Lai, Chih-Ming
;
Liu, Wen Yu
;
Tsay, Jenq-Dar
;
Liu, Po Chun
;
Guo, Yih-Der
A freestanding Gallium Nitride bulk is obtained without using laser lift-off technology. Two techniques such as mask-less ELOG and air-bridge structure are applied on patterned substrate. A self-separated result is successfully demonstrated by using mask-less ELOG and air-bridge structure. Due to the thermal coefficient of expansion (TCE) mismatch between the GaN layer and the non-native (foreign) substrate, separation happens during cooling down after HVPE growth. Both two structures successfully help to lift GaN off the substrate. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.