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- 2018
- differential low noise amplifier
- GaAs pHEMT
- Square Kilometre Array (SKA)
- fully- integrated
- balun
- broadband
- S-band
- Electronic Science and Technology
- National Taiwan University
- Academia Sinica
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Accurate and efficient analysis of the upward heat flow in InGaP/GaAs HBTs through an automated FEM-based tool and Design of Experiments
摘要： This paper presents an extensive analysis aimed at quantifying the impact of all the key technology parameters on the upward heat flow in state‐of‐the‐art InGaP/GaAs heterojunction bipolar transistors (HBTs) for various emitter areas and shapes. Extremely accurate thermal simulations are conducted in a relatively short time with a tool relying on a commercial 3‐D finite‐element method (FEM) solver and an in‐house routine for automated geometry construction, optimized mesh generation, sequential solution, and data storing/processing. Design of Experiments is used to define a thermal resistance model as a function of the aforementioned parameters on the basis of a few FEM data.
关键词： finite‐element method (FEM),gallium arsenide (GaAs),Design of Experiments (DOE),thermal simulation,thermal resistance,heterojunction bipolar transistor (HBT)
更新于2025-09-04 15:30:14
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Fano resonance between coherent acoustic phonon oscillations and electronic states near the bandgap of photoexcited GaAs
摘要： Impulsive photo-excitation of solids results in a travelling strain pulse which manifests itself as coherent acoustic phonon oscillations. These oscillations have been extensively studied using time-resolved pump-probe spectroscopy. In the present work, we report the generation of extremely long-lived, coherent longitudinal acoustic phonon oscillations in intrinsic GaAs (100), with clear and unambiguous evidence of Fano interference between these oscillations and the continuum of electronic states close to the bandgap. Fano resonance is a widespread phenomenon observed in atomic systems and condensed media that arises from quantum interference between a continuum of quantum states and a discrete quantum state. Among other techniques, Fano resonance has been investigated with respect to optical phonons studied with Raman Spectroscopy. In the present work, we investigate Fano resonance in coherent phonon oscillations generated without the aid of any capping layer, dopants or substrate/interface effects. Since Fano resonance is sensitive to changes in electronic structure, doping and defects, these observations are important to the field of picosecond ultrasonics which is used for non-destructive depth profiling of solids and for carrier diffusion studies.
关键词： GaAs,coherent acoustic phonon oscillations,Fano resonance,quantum interference,pump-probe spectroscopy
更新于2025-09-04 15:30:14
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The Effect of Charge Transport Mechanisms on the Efficiency of AlxGa1 – xAs/GaAs Photodiodes
摘要： Photovoltaic characteristics of heterostructure AlxGa1 – xAs/GaAs p–i–n photodiodes fabricated by molecular-beam epitaxy have been studied. Efficiencies of 50% were reached in conversion of monochromatic light in the photovoltaic mode at power density of up to 200 W/cm2 at a wavelength λ = 830 nm. A relationship was demonstrated between the “saturation currents” for the diffusion-related charge-transport mechanism (Shockley) in p–i–n photodiodes, calculated from dark current–voltage characteristics, and the experimental values of efficiency. As the “saturation current” of the diffusion-related charge-transport mechanism increases by an order of magnitude, a relative decrease in the efficiency from the maximum value by more than 10% is observed under excitation by constant or pulsed monochromatic light.
关键词： efficiency,charge transport mechanisms,molecular-beam epitaxy,photodiodes,AlxGa1 – xAs/GaAs
更新于2025-09-04 15:30:14
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[IEEE 2018 13th European Microwave Integrated Circuits Conference (EuMIC) - Madrid, Spain (2018.9.23-2018.9.25)] 2018 13th European Microwave Integrated Circuits Conference (EuMIC) - GaAs Balanced Amplifier for Ka-Band Space Communications System
摘要： The paper deals with the development of a state-of-the-art medium level amplifier able to combine good noise performance with a high P1dB compression point. The MMIC is realized with a balanced structure and making use of the PH25 GaAs pHEMT process provided by UMS. The balanced structure allows to achieve a gain of 19 dB with a P1dB compression point greater than 15 dBm and a noise figure of about 3 dB in a large bandwidth spanning from 26.5 GHz to 31.5 GHz. The chip has a single bias pad; the input and output bond wires are directly matched on chip, so easingenhancing the mechanical integration in the front-end.
关键词： Ka-band,GaAs technology,Balanced amplifier,Space technology,dynamic range
更新于2025-09-04 15:30:14
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High-performance GaAs nanowire cathode for photon-enhanced thermionic emission solar converters
摘要： GaAs nanowire cathodes with exponential doping and graded Al composition structures are proposed for photon-enhanced thermionic emission (PETE) devices. The conversion ef?ciency models with these two nanowire cathodes are deduced on the basis of one-dimensional continuity equations. The conversion ef?ciency as a function of wire length, wire width, Al composition distribution, cathode temperature, emissive surface and back interface recombination velocity are also simulated, respectively. Results show that exponential doping and graded Al composition cathode structures can obviously improve the conversion ef?ciency of devices through introducing a built-in electric ?eld along the growth direction of nanowire. Besides, the optimum wire length and wire width range are 300–340 nm and 5.9–6.4 lm, respectively. Moreover, wider Al composition range is bene?cial to achieve higher conversion ef?ciency. These simulations provide an interesting attempt to explore the working mechanism of GaAs nano-based PETE devices and are expected to be veri?ed by the experimental results in the future.
关键词： exponential doping,graded Al composition,photon-enhanced thermionic emission,GaAs nanowire,conversion efficiency
更新于2025-09-04 15:30:14
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Photoluminescence from GaAs nanostructures
摘要： The confinement properties of semiconductor nanostructures have promising potential in technological application. The main objective of this study is to describe the dependence of Photoluminescence (PL) intensity on different parameters like temperature, excitation wavelength, time and photon energy of GaAs quantum dots (QDs). The model equations are numerically analyzed and simulated with matlab and FORTRAN codes. The experimental fitted values and physical properties of materials are used as data source for our simulation. The result shows that at low temperature the peak is quite sharp, as temperature increases the PL intensity decreases and get quenched at particular thermal energy.
关键词： quantum confinement,Photoluminescence (PL) intensity,GaAs quantum dots,nanostructures,thermal quenching energy
更新于2025-09-04 15:30:14
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A Compact Ka-Band Integrated Doherty Amplifier With Reconfigurable Input Network
摘要： In this paper, we present the design of an ultracompact monolithic millimeter-wave integrated circuit Doherty power amplifier (DPA) using a novel reconfigurable input network at Ka-band. The proposed input network is formed by a compact broadside coupler and two additional field-effect transistors. By reconfiguring the relative phase offset between the main and auxiliary amplifiers, the DPA can be postoptimized to achieve high efficiency and maximal power gain flatness. More importantly, the DPA can be tuned for the highest performance at different frequencies. To verify the concept, a DPA is fabricated in a 0.15-μm enhancement mode Gallium Arsenide (GaAs) process and exhibits a measured output power of 26.5 dBm and gain of 11.8 dB at 28 GHz. The peak power-added efficiency (PAE) is 42%, and the PAE at 6-dB output power backoff (PBO) is 31%, respectively. With reconfigurable capability, the DPA can maintain high performance over a 3-GHz frequency band from 26.5 to 29.5 GHz. To the best of the authors’ knowledge, the proposed DPA achieves among the highest backoff PAE over a wide bandwidth at Ka-band.
关键词： reconfigurable,Ka-band,gallium arsenide (GaAs),Doherty power amplifier (DPA),millimeter-wave integrated circuit (MMIC),Compact coupler
更新于2025-09-04 15:30:14
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Epitaxial GaAs and pHEMT on aluminum-transformed AlAs nanofilms
摘要： Heterogeneous epitaxial growth between semiconductors and metals boosts novel device development and enables various applications. In this work, we have investigated the epitaxial growth of GaAs layers on top of a nanoscale aluminium-transformed AlAs film. The grown GaAs layers are single-crystalline and of high-quality, that has been evidenced by using various material characterization methods and by fabricating their high-electron mobility transistors. We found that an intriguing process named as “arsenidation” of aluminium film plays a key role in the successful epitaxy. Our work opens a window for growing semiconductor/metal hetero-structures for various device applications in the future.
关键词： epitaxial growth,pHEMT,arsenidation,AlAs,GaAs
更新于2025-09-04 15:30:14
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First-Principles Study of Point Defects in GaAs/AlAs Superlattice: the Phase Stability and the Effects on the Band Structure and Carrier Mobility
摘要： Advanced semiconductor superlattices play important roles in critical future high-tech applications such as aerospace, high-energy physics, gravitational wave detection, astronomy, and nuclear related areas. Under such extreme conditions like high irradiative environments, these semiconductor superlattices tend to generate various defects that ultimately may result in the failure of the devices. However, in the superlattice like GaAs/AlAs, the phase stability and impact on the device performance of point defects are still not clear up to date. The present calculations show that in GaAs/AlAs superlattice, the antisite defects are energetically more favorable than vacancy and interstitial defects. The AsX (X = Al or Ga) and XAs defects always induce metallicity of GaAs/AlAs superlattice, and GaAl and AlGa antisite defects have slight effects on the electronic structure. For GaAs/AlAs superlattice with the interstitial or vacancy defects, significant reduction of band gap or induced metallicity is found. Further calculations show that the interstitial and vacancy defects reduce the electron mobility significantly, while the antisite defects have relatively smaller influences. The results advance the understanding of the radiation damage effects of the GaAs/AlAs superlattice, which thus provide guidance for designing highly stable and durable semiconductor superlattice based electronic and optoelectronics for extreme environment applications.
关键词： Point defect,Electrical properties,GaAs/AlAs superlattice,Hybrid density functional theory
更新于2025-09-04 15:30:14
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Influence of Boron Antisite Defects on the Electrical Properties of MBE‐Grown GaAs Nanowires
摘要： Nanowires provide a platform for the integration of heterogeneous materials in III–V systems grown on Si. BxGa1(cid:1)xAs is an interesting material for strain applications, which has not yet been studied in nanowire form. The incorporation of boron in GaAs nanowires is investigated via DC-IV measurements. In transmission electron microscopy analysis a high concentration of boron is found at the nanowire edges, indicating surface segregation during growth. Nanowires grown under boron flux are found to exhibit Ohmic contacts and low contact resistances with p-type metallizations such as Au/Zn/Au or Cr/Au. Back-gated measurements confirmed the p-type behavior of such nanowires, indicating that boron is incorporated on antisite defects where it acts as a doubly-charged acceptor. This offers a new route for the inclusion of p-doped layers in GaAs-based nanowire heterostructures and the subsequent formation of Ohmic contacts.
关键词： boron doping,B:GaAs,nanowires,molecular beam epitaxy
更新于2025-09-04 15:30:14