Browsing by Author "Lee, Chien-Ping"

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2D Numerical Simulation for InGaP/GaAs HBT Safe Operating Area
(2014-01-01)
Lin, Bo-Rong
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Tao, Nick G. M.
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Lee, Chien-Ping
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Henderson, Tim
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Lin, Barry J. F.
The safe operating area (SOA) of InGaP/GaAs heterojunction bipolar transistors (HBT) has been studied using two-dimensional (2D) Technology Computer-Aided Design (TCAD) tool. The hydrodynamic transport based impact ionization and self-heating models were implemented. The DC simulation result shows two distinct SOA boundary regimes corresponding to different dominant mechanisms, which is in good agreement with analytical modeling and experimental results. The simulation not only gives us insight to the detailed failure mechanisms but also provides guidance for the design of devices with better ruggedness and improved SOA performances.
Anomalous optical magnetic shift of self-assembled GaSb/GaAs quantum dots
(2011-07-01)
Lin, Ta-Chun
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Li, Liang-Chen
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Lin, Sheng-Di
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Suen, Yuen-Wuu
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Lee, Chien-Ping
We report the magneto-photoluminescence (PL) measurement results on type-II self-assembled GaSb/GaAs quantum dots with the magnetic field applied in Faraday and Voigt configurations. The emission of the quantum dots exhibited a typical diamagnetic blueshift when the magnetic field was applied in a Faraday configuration. However, when the magnetic field was in the Voigt configuration, an unusual redshift in the emission peak accompanied with a rapid increase of the PL intensity was observed. Guided by numerical calculations, the magnetic field applied in the Voigt configuration is found to provide an additional vertical confinement to electrons, and therefore, substantially enhance the radiative electron-hole recombination. The resulting decrease of the steady-state hole concentration gives rise to the observed anomalous magnetic redshift. (C) 2011 American Institute of Physics. [doi:10.1063/1.3607973]
Averaging and cancellation effect of high-order nonlinearity of a power amplifier
(2007-12-01)
Lee, Chien-Ping
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Ma, Wenlong
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Wang, Nanlei Larry
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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
Nonlinear distortion of a power amplifier (PA) due to the nonlinear input-output transfer function is studied. The high-order nonlinearity or Fourier components of the output, due to the mixing of input signals, are found to be related to an average integral related to the transfer function, thus giving insight to the cancellation effect of the nonlinearity. A simple formula has been derived to relate the nth-order Fourier component of a nonlinear transfer function with a sinusoidal input to an average integral of the nth-order derivative of the transfer function. The large signal nonlinear distortion of the nth-order can therefore be regarded as a weighted average of the nth-order derivative of the transfer function. For PAs, the averaging effect gives rise to local minima in the intermodulation distortion terms during power sweep because of the cancellation of the positive part and the negative part of the derivative during averaging. We have applied the formula to InGaP heterojunction bipolar transistors PAs and are able to explain most of the observed nonlinear phenomena of the amplifiers.
Carrier dynamics in modulation-doped InAs/GaAs quantum rings
(2013)
Lin, Chien-Hung
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Lin, Shin-Chin
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Sun, Kien Wen
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Lee, Chien-Ping
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應用化學系
Carrier dynamics in undoped and modulation-doped self-assembled InAs/GaAs quantum rings was comprehensively examined through time-resolved photoluminescence techniques at room temperature. After photoexcitation, the rates of carrier capture and relaxation in the ground state and excited states were equally fast in both the undoped and charged quantum rings. Instead of cascading down through the excited states, the carriers excited in the undoped quantum rings relaxed through the quasicontinuum states via coupling with acoustical phonons and eventually thermalized to the ground state by emitting longitudinal optical phonons. The dynamics of carrier thermalization was governed by cold carriers in the charged quantum rings. In carrier recombination, the undoped quantum rings had a shorter PL decay time and lower luminescence intensity than the charged quantum rings because radiative recombination was suppressed by defects in the matrix and the absence of cold carriers.
Characteristics of surface plasmon coupled quantum well infrared photodetectors
(2017-06-28)
Hsu, Wei-Cheng
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Ling, Hong-Shi
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Wang, Shiang-Yu
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Lee, Chien-Ping
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電機學院
Quantum Well Infrared Photodetectors (QWIPs) with different structures were characterized for the study of surface plasmon wave coupling. Detailed comparisons between surface plasmon coupled and etched grating coupled devices were investigated. A bias dependence for the enhancement of the responsivity of surface plasmon coupled devices was found, especially for the samples with non-uniform quantum wells. The non-uniform QWIPs with surface plasmon coupling showed an asymmetric enhancement with respect to the bias directions. Stronger enhancements were shown under the biases when a higher effective electric field region is close to the collector. The change of the photocarrier escape probability due to the narrow coupling bandwidth of the surface plasmon wave is attributed to this unexpected bias dependence. Published by AIP Publishing.
Define high quality Type-I InGaAsSb/AlGaAsSb QW laser fabrication process with high-resolution x-ray diffraction
(2018-01-01)
Cheng, Hui-Wen
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Lin, Chien-Hung
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Lee, Chien-Ping
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電機學院
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電子工程學系及電子研究所
Active InGaAsSb/AlGaAsSb type-I quantum well (QW) compositions acceptable for pseudomorphic growth on GaSb substrates restrict the optical range to below 4 mu m. Increasing the In concentration in active region and growing lattice-matched barrier/cladding layers will reach higher emission wavelength. We need to overcome several issues during fabrication process to ensure this high quality epitaxial layer. In this paper, high-resolution x-ray diffraction (HRXRD) method is used to define optimal epitaxy parameters for stable type-I GaSb-based mid infrared laser structures.
Dependence of Performance of Surface Plasmon Coupled Quantum Well Infrared Photodetectors on Doping
(2018-11-01)
Hsu, Wei-Cheng
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Ling, Hong-Shi
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Wang, Shiang-Yu
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Lee, Chien-Ping
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電子工程學系及電子研究所
Three samples of Quantum Well Infrared Photodetectors (QWIPs) with different well doping were proposed for comparison between metallic grating and etched grating. All different doping samples with detectivity 1x10(11) cm*Hz(0.5)/W were achieved under 77 K with metallic grating and the highest detectivity was 2.92x10(11) cm*Hz(0.5)/W with 3.3E17 cm(-3) well doping. The metallic grating samples showed a different quantum efficiency (QE) increment behavior from the etched grating samples as we increased the well doping. The QE enhancement of metallic grating sample was smaller than that in positive bias due to the potential spike between the AlGaAs/GaAs interface. The metallic grating device is more sensitive to the extra barrier between the AlGaAs/GaAs interface because of a narrower coupling bandwidth of surface plasmon. Though the enhancement varied between different samples as we changed the well dopings, the detectivity could still be kept within a reasonable range, which is important for focal plane array applications.
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.
Dual-wavelength GaSb-based mid infrared photonic crystal surface emitting lasers
(2018-03-07)
Li, Zong-Lin
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Chang, Bing-Hui
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Lin, Chien-Hung
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Lee, Chien-Ping
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電機學院
We demonstrate dual-wavelength GaSb-based mid-infrared photonic crystal surface emitting lasers at room temperature. The two lasing peaks emitted simultaneously at 2.3 mu m and 2.22 mu m under optical pumping. Type-I InGaAsSb quantum wells were used for the active region. The photonic crystal with a rectangular lattice was fabricated on the surface to provide light coupling for laser operation. The two-wavelength operation was a result of the resonances from the two different grating periods along the two perpendicular directions of the rectangular lattice. The laser emissions from these two wavelengths were highly linearly polarized in two perpendicular directions as a result of the grating design. Published by AIP Publishing.
Effect of Etching Depth on Threshold Characteristics of GaSb-Based Middle Infrared Photonic-Crystal Surface-Emitting Lasers
(2019-03-14)
Li, Zong-Lin
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Lin, Shen-Chieh
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Lin, Gray
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Cheng, Hui-Wen
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Sun, Kien-Wen
We study the effect of etching depth on the threshold characteristics of GaSb-based middle infrared (Mid-IR) photonic-crystal surface-emitting lasers (PCSELs) with different lattice periods. The below-threshold emission spectra are measured to identify the bandgap as well as band-edge modes. Moreover, the bandgap separation widens with increasing etching depth as a result of enhanced diffraction feedback coupling. However, the coupling is nearly independent of lattice period. The relationship between threshold gain and Bragg detuning is also experimentally determined for PCSELs and is similar to that calculated theoretically for one-dimensional distributed feedback lasers.
Effects of crossed states on photoluminescence excitation spectroscopy of InAs quantum dots
(2011-06-02)
Shih, Ching-I
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Lin, Chien-Hung
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Lin, Shin-Chin
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Lin, Ta-Chun
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Sun, Kien Wen
In this report, the influence of the intrinsic transitions between bound-to-delocalized states (crossed states or quasicontinuous density of electron-hole states) on photoluminescence excitation (PLE) spectra of InAs quantum dots (QDs) was investigated. The InAs QDs were different in size, shape, and number of bound states. Results from the PLE spectroscopy at low temperature and under a high magnetic field (up to 14 T) were compared. Our findings show that the profile of the PLE resonances associated with the bound transitions disintegrated and broadened. This was attributed to the coupling of the localized QD excited states to the crossed states and scattering of longitudinal acoustical (LA) phonons. The degree of spectral linewidth broadening was larger for the excited state in smaller QDs because of the higher crossed joint density of states and scattering rate.
Electrically driven integrated photonic crystal nanocavity coupled surface emitting laser
(2007-04-09)
Huang, Shih-Chieh
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Yang, Tsung-Hua
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Lee, Chien-Ping
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Lin, Sheng-Di
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電子工程學系及電子研究所
Single mode surface emitting lasers with photonic crystal nanocavities integrated with electrically driven strained quantum well laser diodes are demonstrated. The photonic crystal serves as an end mirror for the laser cavity, while the nanocavities serve as wavelength selective high Q surface emitters. The laser emission from the nanocavities had excellent temperature stability. The wavelength shift versus temperature was about five times better than that of regular quantum well lasers. Dual wavelength emission from two side by side slightly different cavities was also demonstrated. Laser emission with two wavelengths of Delta lambda=0.8 nm was obtained. (c) 2007 American Institute of Physics.
Electrically pumped quantum dot surface emitting lasers with Bragg grating capped by ITO cladding layers
(2016)
Hong, Kuo-Bin
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Chang, Ting-Yuan
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Pan, Chien-Hung
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Lin, Chien-Hung
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Lin, Gray
QD based Bragg gratings surface emitting lasers using ITO as transparent cladding layers were demonstrated. Measured lasing peak locates at 1298nm and threshold current density of 210 A/cm(2). The laser shows extremely small divergence surface-emitted beam and thermal redshift of 0.08 nm/K in peak wavelength.
Electrooptical Properties of InGaAs/GaAs Strained Single Quantum Wells
(2000)
Lu, Chien-Rong
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Lou, Shry-Fong
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Cheng, Hung-Hsiang
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Lee, Chien-Ping
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Tsai, Fu-Yi
The electrooptical properties of (100) and (111)B InGaAs/GaAs strained single quantum wells have been studied by the photoreflectance spectroscopy at various temperatures and under different biases. There is a Si delta-doping sheet under the GaAs surface to screen the surface built-in electric field from the quantum well. The spectral features consist of the excitonic interband transitions in the quantum well, and the Franz-Keldysh oscillations from the band edge transitions of the GaAs barrier near the surface. The piezoelectric field tilts the (111)B single quantum well toward the Si delta-doping and causes subband filling by the electrons from the delta-doping centers. With a proper external bias to repel electrons from the tilted quantum well, the excitonic interband transition in the (111)B system is enhanced.
Enhanced optical property in quaternary GaInAsSb/AlGaAsSb quantum wells
(2014-10-21)
Lin, Chien-Hung
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Lee, Chien-Ping
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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
High quality GaInAsSb/AlGaAsSb quantum wells (QWs) have been grown by molecular beam epitaxy using proper interface treatments. By controlling the group-V elements at interfaces, we obtained excellent optical quality QWs, which were free from undesired localized trap states, which may otherwise severely affect the exciton recombination. Strong and highly efficient exciton emissions up to room temperature with a wavelength of 2.2 mu m were observed. A comprehensive investigation on the QW quality was carried out using temperature dependent and power dependent photoluminescence (PL) measurements. The PL emission intensity remains nearly constant at low temperatures and is free from the PL quenching from the defect induced localized states. The temperature dependent emission energy had a bulk-like behavior, indicating high quality well/barrier interfaces. Because of the uniformity of the QWs and smooth interfaces, the low temperature limit of inhomogeneous line width broadening is as small as 5meV. (C) 2014 AIP Publishing LLC.
Evolution of self-assembled InAs quantum ring formation
(2007-07-15)
Ling, Hong-Shi
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Lee, Chien-Ping
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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 evolution of InAs quantum ring (QR) formation and the corresponding optical properties were investigated by atomic force microscopy (AFM) and photoluminescence (PL) spectroscopy. Just like a nanoscale volcanic eruption, the transformation from quantum dots (QDs) to QRs using the capping and annealing process depends on how much InAs is removed from the center of the dots to the surrounding areas. The final structure was found to depend on the annealing temperature and the cap layer thickness. We have investigated the QR formation at different stages using various growth conditions. The findings provided a clear picture on the mechanism of ring formation. We were able to obtain QRs with various geometries by controlling these growth parameters. (c) 2007 American Institute of Physics.
Experimental Observation of Inflection-Point Slow Light Modes in Photonic Crystal Coupled Waveguides
(2007)
Huang, Shih-Chieh
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Kato, Masao
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Kuramochi, Eiichi
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Lee, Chien-Ping
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Notomi, Masaya
We report on the time-domain measurement of inflection-point slow light modes in a photonic crystal coupled waveguide. The S type band structure for the waveguide mode allows a unique opportunity for slow light measurement. (C) 2007 Optical Society of America
Fe Doped Magnetic Nanodiamonds Made by Ion Implantation as Contrast Agent for MRI
(2018-05-04)
Lin, Bo-Rong
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Chen, Chien-Hsu
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Kunuku, Srinivasu
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Chen, Tzung-Yuang
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Hsiao, Tung-Yuan
We report in this paper a new MRI contrast agent based on magnetic nanodiamonds fabricated by Fe ion implantation. The Fe atoms that are implanted into the nanodiamonds are not in direct contact with the outside world, enabling this new contrast agent to be free from cell toxicity. The image enhancement was shown clearly through T2 weighted images. The concentration dependence of the T2 relaxation time gives a relaxivity value that is about seven times that of the regular non-magnetic nanodiamonds. Cell viability study has also been performed. It was shown that they were nearly free from cytotoxicity independent of the particle concentration used. The imaging capability demonstrated here adds a new dimension to the medical application of nanodiamonds. In the future one will be able to combine this capability of magnetic nanodiamonds with other functions through surface modifications to perform drug delivery, targeted therapy, localized thermal treatment and diagnostic imaging at the same time.
Fluorescent B-10 embedded nanodiamonds as B-10 delivery agent for boron neutron capture therapy
(2019-06-26)
Lin, Bo-Rong
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Kunuku, Srinivasu
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Chen, Tzung-Yuang
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Chang, Yu-Jen
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Liao, Li-Chuan
Boron neutron capture therapy is a potentially powerful anti-cancer treatment, the success of which depends heavily on the boron delivery agent. Enabling the real-time tracing of delivery agents as they move through the body is crucial to the further development of boron neutron capture therapy. In this study, we fabricate fluorescent B-10 embedded nanodiamonds using physical ion implantation in conjunction with a two-step annealing process. Fluorescent B-10 embedded nanodiamonds perform well in cell viability test. The red fluorescence of the B-10 embedded nanodiamonds allows their use in fluorescence microscopy and in vivo imaging systems, thereby making it possible to conduct tracking in real time. The proposed fluorescent B-10 embedded nanodiamonds, combining optical visibility and B-10 transport capability, might be a promising boron delivery agent suitable for a wide range of biomedical applications.
Fluorescent Fe Embedded Magnetic Nanodiamonds Made by Ion Implantation
(2019-02-04)
Lin, Bo-Rong
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Kunuku, Srinivasu
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Chen, Chien-Hsu
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Chen, Tzung-Yuang
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Hsiao, Tung-Yuan
We demonstrate fluorescent Fe embedded magnetic nanodiamonds by ion implantation and two-step annealing. The diamond characteristics with a highly ordered core and a graphite surface layer are maintained after the implantation process. After the two-step annealing process, a bright red fluorescence associated with nitrogen-vacancy centers is observed. These new fluorescent magnetic nanodiamonds can be used as a dual-function in vivo tracer with both optical visibility and magnetic resonance imaging capabilities. They are potentially useful for the more advanced in vivo biological and medical applications.