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Analysis and design of wideband active power splitter with interleaf transmission line topology
(2019-11-01)
Huang, Ching-Ying
;
Hu, Robert
;
Niu, Dow-Chi
;
Chang, Chi-Yang
;
電機學院
This article proposes a new wideband active power splitter design where the gain cells along the input transmission line are arranged in interleaf rather than the conventional parallel style, thus the circuit's high-frequency performance can be greatly improved. Both theoretical analysis and circuit simulation have been carried out; as a demonstration, parallel and interleaf active power splitters are designed using 0.1 mu m GaAs pseudo-morphic heterostructure field effect transistors (GaAs pHEMT) process and measured on-wafer. The results clearly indicate the superiority of the interleaf topology. A 40 GHz interleaf active power splitter in 90 nm complementary metal-oxide-semiconductor (CMOS) is then presented where the magnitude and phase imbalance between the two output ports are 0.15 dB and 2.6 degrees at 20 GHz, and 0.16 dB and 14 degrees at 40 GHz. The output-port isolation is better than 30 dB across the whole frequency range.
Single-exciton energy shell structure in InAs/GaAs quantum dots
(2008-12-01)
Awirothananon, S.
;
Raymond, S.
;
Studenikin, S.
;
Vachon, M.
;
Render, W.
The energy shell structure of a single exciton confined in a self-assembled quantum dot (QD), including excited states, is studied in a regime where the direct Coulomb attraction energy is comparable to the kinetic energy of the carriers. This is achieved via magnetophotoluminescence excitation spectroscopy experiments, where a magnetic field applied perpendicular to the plane of the QD is used to reveal the angular-momentum content of energy shells. The absorption spectrum of the QDs is modeled, and comparison with experiment allows us to relate the observed transitions to interband QD bound-state transitions. The blueshift of the absorption peaks compared to the emission peaks is then interpreted in terms of many-body interactions, and we show that for a highly symmetric situation, the observed energy difference gives a direct measurement of the extra exchange energy gained upon addition of an extra exciton in the QD.
Impacts of structural asymmetry on the magnetic response of excitons and biexcitons in single self-assembled In(Ga)As quantum rings
(2009-08-01)
Lin, Ta-Chun
;
Lin, Chia-Hsien
;
Ling, Hong-Shi
;
Fu, Ying-Jhe
;
Chang, Wen-Hao
The diamagnetic shifts of neutral excitons and biexcitons confined in single self-assembled In(Ga)As/GaAs quantum rings are investigated. Unlike quantum dots, quantum rings reveal a considerably large biexciton diamagnetic shift, about two times larger than that of single excitons. Based on model calculations, we found that the inherent structural asymmetry and imperfection, combined with the interparticle Coulomb interactions, is the fundamental cause of the more extended biexciton wave function in the quantum rings. The exciton wave function tends to be localized in one of the potential valleys induced by structural imperfections of the quantum ring due to the strong localization of hole and the electron-hole Coulomb attraction, resembling the behavior in single dots. Our results suggest that the phase coherence of neutral excitons in quantum rings will be smeared out by such wave function localizations.
The influences of surface treatment and gas annealing conditions on the inversion behaviors of the atomic-layer-deposition Al2O3/n-In0.53Ga0.47As metal-oxide-semiconductor capacitor
(2010-07-26)
Trinh, H. D.
;
Chang, E. Y.
;
Wu, P. W.
;
Wong, Y. Y.
;
Chang, C. T.
The inversion behaviors of atomic-layer-deposition Al2O3/n-In0.53Ga0.47As metal-oxide-semiconductor capacitors are studied by various surface treatments and postdeposition annealing using different gases. By using the combination of wet sulfide and dry trimethyl aluminum surface treatment along with pure hydrogen annealing, a strong inversion capacitance-voltage (C-V) response is observed, indicating a remarkable reduction in interface trap state density (D-it) at lower half-part of In0.53Ga0.47As band gap. This low D-it was confirmed by the temperature independent C-V stretch-out and horizontal C-V curves. The x-ray photoelectron spectroscopy spectra further confirm the effectiveness of hydrogen annealing on the reduction of native oxides. (C) 2010 American Institute of Physics. [doi:10.1063/1.3467813]
Analysis of two-phonon infrared spectral features of gallium arsenide and indium phosphide by first-principles calculations
(2014-12)
Lin, Huang-Hsiang
;
Chung, Pei-Kang
;
Yen, Shun-Tung
;
電機學院
;
電子工程學系及電子研究所
We perform a self-consistent calculation based on density functional perturbation theory to analyze the infrared spectral features of GaAs and InP arising from two-phonon processes. The features are identified and assigned the critical points in the first Brillouin zone. Distribution of the critical points is investigated. The analysis demonstrates that collections of phonons of wave vectors around symmetry points and along symmetry lines are responsible for strong infrared features in two-phonon processes.
Dependence of energy gap on magnetic field in semiconductor nano-scale quantum rings
(2003-06-10)
Li, YM
;
Lu, HM
;
Voskoboynikov, O
;
Lee, CP
;
Sze, SM
We study the electron and hole energy states for a complete three-dimensional (3D) model of semiconductor nanoscale quantum rings in an external magnetic field. In this study, the model formulation includes: (i) the position dependent effective mass Hamiltonian in non-parabolic approximation for electrons, (ii) the position dependent effective mass Hamiltonian in parabolic approximation for holes, (iii) the finite hard wall confinement potential, and (iv) the Ben Daniel-Duke boundary conditions. To solve this 3D non-linear problem, we apply the non-linear iterative method to obtain self-consistent solutions. We find a non-periodical oscillation of the energy band gap between the lowest electron and hole states as a function of external magnetic fields. The result is useful in describing magneto-optical properties of the nano-scale quantum rings. (C) 2003 Elsevier Science B.V. All rights reserved.
Vertical coupling effects and transition energies in multilayer InAs/GaAs quantum dots
(2004-09-20)
Li, YM
;
友訊交大聯合研發中心
;
D Link NCTU Joint Res Ctr
We investigate the transition energy of vertically stacked semiconductor quantum dots with a complete three-dimensional (3D) model in an external magnetic field. In this study, the model formulation includes: (1) the position-dependent effective mass Hamiltonian in non-parabolic approximation for electrons, (2) the position-dependent effective mass Hamiltonian in parabolic approximation for holes, (3) the finite hard-wall confinement potential, and (4) the Ben Daniel-Duke boundary conditions. To solve the nonlinear problem, a nonlinear iterative method is implemented in our 3D nanostructure simulator. For multilayer small InAs/GaAs quantum dots, we find that the electron-hole transition energy is dominated by the number of stacked layers. The inter-distance d plays a crucial role in the tunable states of the quantum dots. Under zero magnetic field for a 10-layer QDs structure with d = 1.0 nm, there is about 30% variation in the electron ground state energy. Dependence of the magnetic field on the electron-hole transition energy is weakened when the number of stacked layers is increased. Our investigation is constructive in studying the magneto-optical phenomena and quantum optical structures. (C) 2004 Elsevier B.V. All rights reserved.
Transition mechanism of InAs/GaAs quantum-dot infrared photodetectors with different InAs coverages
(2010-05-01)
Tseng, Chi-Che
;
Chung, Tung-Hsun
;
Mai, Shu-Cheng
;
Chao, Kuang-Ping
;
Lin, Wei-Hsun
In this article, the authors investigate the influences of different InAs coverages on the photoluminescence excitation (PLE) spectra and spectral responses of InAs/GaAs quantum-dot infrared photodetectors (QDIPs). An increase in InAs coverage would lead to an increase in energy separation between heavy-hole state and light-hole state in the wetting layer (WL) region in the QD PLE spectra. The results suggest that most of the strain resulted from the InAs/GaAs lattice mismatch may be accumulated in the WL instead of the QD region. Also observed are the similar energy separations of energy levels responsible for the intraband absorption in the PLE spectra of the QDIPs such that similar detection wavelengths are observed for the devices. [DOI:10.1116/1.3368607]
The transition mechanisms of a ten-period InAs/GaAs quantum-dot infrared photodetector
(2008-11-01)
Tseng, Chi-Che
;
Chou, Shu-Ting
;
Lin, Shin-Yen
;
Chen, Cheng-Nan
;
Lin, Wei-Hsun
This study explores the growth and effects of a ten-period InAs/GaAs quantum-dot infrared photodetector (QDIP). With a uniform quantum-dot (QD) size distribution and a QD density of 2.8x10(10) cm(-2), this 10 K photoluminescence spectrum shows a peak energy at 1.07 eV and a narrow full width at half maximum of 31.7 meV. The QDIP exhibits an asymmetric response under different voltage polarities and a high responsivity of 1.7 A/W at -1.1 V. Another noticeable observation in the spectral response of the device is the 6 mu m peak detection wavelength with a high spectral broadening Delta lambda/lambda of 0.67. By analyses of the photoluminescence excitation spectrum and the temperature dependence of spectral response, the wide spectral response of the QDIP is attributed to the summation of transitions between QD excited states and the wetting layer states, instead of transitions between QD ground state and higher excited states.
Electric-field-controlled electron relaxation in lateral double quantum dots embedded in a suspended slab
(2008-11-15)
Liao, Y. Y.
;
Chuu, D. S.
;
Jian, S. R.
;
電子物理學系
;
Department of Electrophysics
This study investigates phonon-induced electron relaxation in a lateral double quantum dot that is embedded in a suspended slab. Exact calculations are made in electric fields. The dependence of the relaxation rate on the parameters of the dots and the slabs is analyzed. Numerical results indicate that the relaxation rate depends strongly on the phonon character of the slab. Unlike in the bulk environment, phonon-subband quantization clearly influences the behavior. In particular, the relaxation rate can be greatly suppressed or enhanced by tuning the electric fields. This fact may be useful in manipulating the relaxation rate in lateral double quantum dots.

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