Browsing by Author "Wang, S. -C."

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Defect selective passivation in GaN epitaxial growth and its application to light emitting diodes
(2009-11-23)
Lo, M. -H.
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Tu, P. -M.
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Wang, C. -H.
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Cheng, Y. -J.
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Hung, C. -W.
A defect selective passivation method to block the propagation of threading dislocations in GaN epitaxial growth is demonstrated. The defect selective passivation is done by using defect selective chemical etching to locate defect sites, followed by silicon oxide passivation of the etched pits, and epitaxial over growth. The threading dislocation density in the regrown epilayer is significantly improved from 1x10(9) to 4x10(7) cm(-2). The defect passivated epiwafer is used to grow light emitting diode and the output power of the fabricated chip is enhanced by 45% at 20 mA compared to a reference one without using defect passivation.
Enhanced electron-hole plasma stimulated emission in optically pumped gallium nitride nanopillars
(2011-03-21)
Lo, M. -H.
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Cheng, Y. -J.
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Kuo, H. -C.
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Wang, S. -C.
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光電工程學系
An enhanced stimulated emission was observed in optically pumped GaN nanopillars. The nanopillars were fabricated from an epitaxial wafer by patterned pillar etching followed by crystalline regrowth. Under optical excitation, a strong redshifted stimulated emission peak emerged from a broad spontaneous emission background. The emission is attributed to the electron-hole plasma gain at high carrier density. The emission slope efficiency was greatly enhanced by 20 times compared with a GaN substrate under the same pumping condition. The enhancement is attributed to the better photon and gain interaction from the multiple scattering of photons among nanopillars. (C) 2011 American Institute of Physics. [doi:10.1063/1.3570634]
Numerical study of optical properties of InGaN multi-quantum-well laser diodes with polarization-matched AlInGaN barrier layers
(2009-04-01)
Chen, J. -R.
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Ling, S. -C.
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Huang, H. -M.
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Su, P. -Y.
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Ko, T. -S.
The optical properties of InGaN multi-quantum-well laser diodes with different polarization-matched AlInGaN barrier layers have been investigated numerically by employing an advanced device simulation program. The use of quaternary polarization-matched AlInGaN barrier layers enhances the electron-hole wave function overlap due to the compensation of polarization charges between InGaN quantum well and AlInGaN barrier layer. According to the simulation results, it is found that, among the polarization-matched quantum-well structures under study, lower threshold current and higher slope efficiency can be achieved simultaneously when the aluminum composition in AlInGaN barrier layers is about 10-15%. The optimal polarization-matched InGaN/AlInGaN laser diode shows lower threshold current and higher slope efficiency compared to conventional InGaN/InGaN laser diodes.