Browsing by Author "Chen, J. -R."

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Broadening of upper polariton branch in GaAs, GaN, and ZnO semiconductor microcavities
(2011-04-01)
Lin, S. -C.
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Chen, J. -R.
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Lu, T. -C.
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光電工程學系
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Department of Photonics
The well-distinguished lower polariton branches (LPBs) and upper polariton branches (UPBs) are characteristics of strong coupling in semiconductor microcavities (MCs). In practice, however, the UPBs are often broadening especially in wide-bandgap material MCs. We present in detail the possible physical mechanisms for the broadening of UPBs for different designs of MCs by numerical simulations based on GaAs, GaN and ZnO materials. The calculated results show that the UPBs of the GaN- and ZnO-based MCs will become indistinct when the thickness of optical cavity is larger than lambda and 0.25 lambda, respectively, mainly attributed to the larger product of the absorption coefficient and the active layer thickness. In wide-bandgap materials, it would be relatively easier to observe the UPB in the case of negative exciton-cavity mode detuning due to the exciton-like UPB and lower absorption of scattering states. In addition, the inhomogeneous broadening would be an important factor causing the invisible UPB in wide-bandgap semiconductor MCs. We demonstrate that in multiple quantum well embedded ZnO-based MCs, the UPB could be well defined due to the large 2D exciton binding energy and the small product of absorption coefficient and active layer thickness. These results show that the UPBs can be properly defined in wide-bandgap semiconductor MCs by appropriate design of the MC structures.
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.
Numerical study on strained InGaAsP/InGaP quantum wells for 850-nm vertical-cavity surface-emitting lasers
(2007-03-01)
Kuo, Y. -K.
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Chen, J. -R.
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Chen, M. -L.
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Liou, B. -T.
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光電工程學系
The physical and optical properties of compressively strained InGaAsP/InGaP quantum wells for 850-nm vertical-cavity surface-emitting lasers are numerically studied. The simulation results show that the maximum optical gain, transparency carrier densities, transparency radiative current densities, and differential gain of InGaAsP quantum wells can be efficiently improved by employing a compressive strain of approximately 1.24% in the InGaAsP quantum wells. The simulation results suggest that the 850-nm InGaAsP/InGaP vertical-cavity surface-emitting lasers have the best laser performance when the number of quantum wells is one, which is mainly attributed to the non-uniform hole distribution in multiple quantum wells due to high valence band offset.