Browsing by Author "Huang, Shyh-Jer"

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Discrete monolayer light emission from GaSb wetting layer in GaAs
(2007-06-11)
Lo, Ming-Cheng
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Huang, Shyh-Jer
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Lee, Chien-Ping
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Lin, Sheng-Di
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Yen, Shun-Tung
Distinct light emission peaks from monolayers of GaSb quantum wells in GaAs were observed. Discrete atomic layers of GaSb for the wetting layer prior to quantum dot formation give rise to transition peaks corresponding to quantum wells with 1, 2, and 3 ML. From the transition energies the authors were able to deduce the band offset parameter between GaSb and GaAs. By fitting the experimental data with the theoretical calculated result using an 8x8 k center dot p Burt's Hamiltonian along with the Bir-Picus deformation potentials, the strain-free (fully strained) valence band discontinuity for this type-II heterojunction was determined to be 0.45 eV (0.66 eV). (c) 2007 American Institute of Physics.
Electron spillover effects in InGaN/GaN quantum-well lasers
(2007-12-01)
Huang, Shyh-Jer
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Yen, Shun-Tung
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
The effects of electron spillover from quantum wells on the optical property of InGaN/GaN laser diodes are theoretically studied in detail. A six-band model including strain effects is used to calculate valence band states. Continuous subbands unconfined to the quantum wells are simulated deliberately by densely discretized subbands for the spillover electrons. The calculation results show obvious differences in the radiative current densities and the gain spectra between the cases with and without considering the spillover effect. We further investigate the spillover effect on the radiative current densities and the spontaneous emission spectra, with variations in the depth and the width of quantum wells, the total loss of the cavity, and the temperature. For shallow wells, the spillover effect is particularly important. It broadens both the gain and the spontaneous emission spectra and hence deteriorates the threshold of laser diodes. Such an effect can be alleviated by employing a long cavity and a multi-quantum-well active region. The concept of the electron spillover studied in this work is not only applicable to the nitride lasers but also to other kinds of quantum-well lasers. (C) 2007 American Institute of Physics.
Improvement in threshold of InGaN/GaN quantum-well lasers by p-type modulation doping
(2007-12-01)
Huang, Shyh-Jer
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Yen, Shun-Tung
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The optical properties of modulation-doped InGaN/GaN laser diodes are theoretically studied with the effects of electron spillover from quantum wells considered. We use a six-band model including the strain effect for calculating valence band states. The continuous subbands are treated by a dense discretization for the electrons spilling from the quantum wells. The calculation results show that the threshold current can be significantly reduced by p-type modulation doping around the wells but not by n-type doping, supposed that the layers are of a perfect quality and the impurity-induced defects are ignored. Also, the p-type modulation doping can make the threshold current more insensitive to the cavity loss compared with other cases. An optimized threshold current density can be achieved for single-quantum-well lasers by introducing p-type dopants. However, the dopant concentration is high and may be inaccessible. For double-quantum-well lasers an optimized low threshold current can be achieved with a slighter and practicable p-type doping level. (C) 2007 American Institute of Physics.
Light emission characteristics of nonpolar a-plane GaN-based photonic crystal defect cavities
(2015-01-01)
Kao, Tsung Sheng
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Wu, Tzeng-Tsong
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Tsao, Che-Wei
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Lin, Jyun-Hao
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Lin, Da-Wei
In this paper, nonpolar a-plane GaN-based photonic crystals (PCs) with different defect cavities have been demonstrated. By using a micro-photoluminescence (mu-PL) system operated at 77 K, the dominant resonant modes of the GaN-based PC defect cavities show high quality factor (Q) values in the light emission performance which can be up to 4.3x10(3). Moreover, the degree of polarization (DOP) of the light emission from the nonpolar GaN-based PC defect cavities was measured to achieve around 64 % along the m crystalline direction.
Light Emission Characteristics of Nonpolar a-Plane GaN-Based Photonic Crystal Defect Cavities
(2016-09)
Kao, Tsung Sheng
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Wu, Tzeng-Tsong
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Tsao, Che-Wei
;
Lin, Jyun-Hao
;
Lin, Da-Wei
In this paper, the light emission performance from nonpolar a-plane gallium nitride (GaN)-based photonic crystal (PC) slabs with line-type defect cavities has been investigated. Via the focused ion beam milling technique, thin membrane structures of the nonpolar GaN PC defect cavities were engineered, exhibiting one dominated resonant mode occurred at 419.3 nm with a high quality factor of 1.9 x 10(3) in the photoluminescence emission characterizations. In the far-field region, light emission performance shows a high polarization degree of 50% with the beam direction perpendicular to the defect cavity. Compared with the PC defect cavity patterns fabricated on c-axial oriented GaN materials, the a-plane PC defect cavities display not only the linear light output-input power dependence, but also an invariant resonant mode of constant light emission behavior with increasing the injection carriers, therefore providing a new perspective for the future development of promising optoelectronic devices.