Browsing by Author "Cheng, Ji-Hao"

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Effects of Laser Sources on Damage Mechanisms and Reverse-Bias Leakages of Laser Lift-Off GaN-Based LEDs
(2009)
Cheng, Ji-Hao
;
Wu, YewChung Sermon
;
Peng, Wei Chih
;
Ouyang, Hao
;
材料科學與工程學系
The frequency-tripled neodymium-doped yttrium aluminum garnet laser (355 nm) and the KrF pulsed excimer laser (248 nm) were employed to separate GaN thin films from sapphire substrates and to transfer the films to bond with other substrates. The different laser lift-off processes would generate the dislocation density on different regions. In this study, the effects of these two laser sources on structural damage mechanisms and reverse-bias leakages of InGaN-GaN light-emitting diodes (LEDs) were studied.
Effects of laser sources on the reverse-bias leakages of laser lift-off GaN-based light-emitting diodes
(2007-06-18)
Wu, Yewchung Sermon
;
Cheng, Ji-Hao
;
Peng, Wei Chih
;
Ouyang, Hao
;
材料科學與工程學系
The KrF pulsed excimer laser (248nm) and the frequency-tripled neodymium doped yttrium aluminum garnet laser (355nm) have been used to separate GaN thin films from sapphire substrates and transfer to bond other substrate. However, these processes would increase the dislocation density, resulting in an increase of the leakage current. In this study, the effects of these two laser sources on the reverse-bias leakages of InGaN-GaN light-emitting diodes were studied. (c) 2007 American Institute of Physics.
Improved crystal quality and performance of GaN-based light-emitting diodes by decreasing the slanted angle of patterned sapphire
(2010-02-01)
Cheng, Ji-Hao
;
Wu, YewChung Sermon
;
Liao, Wei-Chih
;
Lin, Bo-Wen
;
材料科學與工程學系
Periodic triangle pyramidal array patterned sapphire substrates (PSSs) with various slanted angles were fabricated by wet etching. It was found beside normal wurtzite GaN, zinc blende GaN was found on the sidewall surfaces of PSS. The crystal quality and performance of PSS-LEDs improved with decrease in slanted angle from 57.4 degrees to 31.6 degrees. This is because most of the growth of GaN was initiated from c-planes. As the growth time increased, GaN epilayers on the bottom c-plane covered these pyramids by lateral growth causing the threading dislocation to bend toward the pyramids.