Browsing by Author "Chang, W. T."

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Efficiency droop alleviation in InGaN/GaN light-emitting diodes by graded-thickness multiple quantum wells
(2010-11-01)
Wang, C. H.
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Chang, S. P.
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Chang, W. T.
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Li, J. C.
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Lu, Y. S.
InGaN/GaN light-emitting diodes (LEDs) with graded-thickness multiple quantum wells (GQW) was designed and grown by metal-organic chemical vapor deposition. The GQW structure, in which the well-thickness increases along [0001] direction, was found to have superior hole distribution as well as radiative recombination distribution by performing simulation modeling. Accordingly, the experimental investigation of electroluminescence spectrum reveals additional emission from the narrower wells within GQWs. Consequently, the efficiency droop can be alleviated to be about 16% from maximum at current density of 30 to 200 A/cm(2), which is much smaller than that for conventional LED (32%). Moreover, the light output power was enhanced from 18.0 to 24.3 mW at 20 A/cm(2). (C) 2010 American Institute of Physics. [doi:10.1063/1.3507891]
Efficiency droop improvement in GaN-based light-emitting diodes by graded-composition electron blocking layer
(2011)
Wang, C. H.
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Chang, S. P.
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Chang, W. T.
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Li, J. C.
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Kuo, H. C.
A graded-composition electron blocking layer (GEBL) with aluminum composition increasing along [ 0001] direction was designed for c-plane GaN-based light-emitting diodes (LEDs). The simulation results demonstrated that such GEBL can effectively enhance the capability of hole transportation across the EBL as well as the electron confinement. Consequently, the LED with GEBL grown by metal-organic chemical vapor deposition exhibited better electrical characteristics, and much higher output power at high current density, as compared to conventional LED. Meanwhile, the efficiency droop was reduced from 34% in conventional LED to only 4% from the maximum value at low injection current to 200 A/cm(2).
Efficiency Droop Reduction in InGaN/GaN Light-emitting Diodes by Graded-thickness Multiple Quantum Wells
(2011)
Wang, C. H.
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Chang, W. T.
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Chang, S. P.
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Li, J. C.
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Kuo, H. C.
InGaN/GaN LED with graded-thickness MQWs has superior hole and radiative recombination distribution by simulation modeling, and electroluminescence spectrum reveals additional emission from the narrower wells. Output power and efficiency droop behavior are both improved. (C) 2010 Optical Society of America
Hole injection and efficiency droop improvement in InGaN/GaN light-emitting diodes by band-engineered electron blocking layer
(2010-12-27)
Wang, C. H.
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Ke, C. C.
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Lee, C. Y.
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Chang, S. P.
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Chang, W. T.
A graded-composition electron blocking layer (GEBL) with aluminum composition increasing along the [0001] direction was designed for c-plane InGaN/GaN light-emitting diodes (LEDs) by employing the band-engineering. The simulation results demonstrated that such GEBL can effectively enhance the capability of hole transportation across the EBL as well as the electron confinement. Consequently, the LED with GEBL grown by metal-organic chemical vapor deposition exhibited lower forward voltage and series resistance and much higher output power at high current density as compared to conventional LED. Meanwhile, the efficiency droop was reduced from 34% in conventional LED to only 4% from the maximum value at low injection current to 200 A/cm(2). (C) 2010 American Institute of Physics. [doi:10.1063/1.3531753]