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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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Micro-fabricated wideband band-stop filter using GaAs-based integrated passive device technology
摘要： This paper presents a new concept of implementing a micro-fabricated wideband band-stop filter on a gallium arsenide (GaAs) substrate using integrated passive device technology. The incorporation of an air-bridge structure was explored to enhance design flexibility and achieve excellent radio-frequency performance of the filter. A wideband band-stop filter was realized on a GaAs substrate, generating an insertion loss of ? 0.37 dB and a return loss of ? 38 dB with excellent attenuation of ? 28.78 and ? 22.27 dB, in the lower and the upper passband, respectively. The filter resonates at 10.72 GHz, occupying a die area of 2000 μm × 1540 μm. The selectivity of the filter is reflected by its tremendous suppression of out-of-band signals with the existence of attenuation poles in the vicinity of the resonance frequency. Experimental verification of the filter response demonstrates its potential use as an on-chip device operating in the X-band frequency spectrum.
关键词： Gallium arsenide (GaAs),Wideband band-stop filter,Radio frequency (RF),Integrated passive device technology,Micro-fabrication
更新于2025-09-04 15:30:14
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Deterministic switching of the growth direction of self-catalyzed GaAs nanowires
摘要： Typical vapor-liquid-solid growth of nanowires is restricted to vertical one-dimensional geometry, while there is a broad interest for more complex structures in the context of electronics and photonics applications. Controllable switching of the nanowire growth direction opens up new horizons in the bottom-up engineering of self-assembled nanostructures, for example, to fabricate interconnected nanowires used for quantum transport measurements. In this work, we demonstrate a robust and highly controllable method for deterministic switching of the growth direction of self-catalyzed GaAs nanowires. The method is based on the modification of the droplet-nanowire interface in the annealing stage without any fluxes and subsequent growth in the horizontal direction by a twin-mediated mechanism with indications of a novel type of interface oscillations. A 100% yield of switching the nanowire growth direction from vertical to horizontal is achieved by systematically optimizing the growth parameters. A kinetic model describing the competition of different interface structures is introduced to explain the switching mechanism and the related nanowire geometries. The model also predicts that growth of similar structures is possible for all vapor-liquid-solid nanowires with commonly observed truncated facets at the growth interface.
关键词： Growth direction,Surface energetics,Self-catalyzed GaAs nanowires,Crystal facets
更新于2025-09-04 15:30:14
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Controlling ZnSe/GaAs interface properties: The role of elemental exposure and photon irradiation during growth initiation
摘要： Incorporating dissimilar semiconductors into a single platform can offer additional degrees of freedom for optoelectronic device design. However, bonding of elements with mixed valence at heterovalent interfaces often leads to defect formation and poor material quality. Using ZnSe/GaAs as a model system, we investigate the use of above-bandgap photon irradiation in combination with elemental surface treatments as a route to modify the interface properties. We find that this approach produces large changes in the behavior of the interfaces. Specifically, treating the GaAs surface with light and a short exposure to Se flux results in strong excitonic emission from both layers and an abrupt interface between them. We propose that these improvements arise from controlled desorption of As atoms from the GaAs surface and the subsequent Se enrichment of the interface. These results suggest that illumination with above-bandgap photons and proper choice of elemental exposure prior to heterovalent epitaxial layer growth may aid the synthesis of heterovalent semiconductor heterostructures.
关键词： interface properties,photon irradiation,heterovalent interfaces,elemental exposure,ZnSe/GaAs
更新于2025-09-04 15:30:14
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Research on Time Jitter of GaAs Photoconductive Semiconductor Switches in the Negative Differential Mobility Region
摘要： Time jitter of GaAs photoconductive semiconductor switches (PCSS) is investigated at an optical excitation of 1053 nm wavelength and 500 ps pulse duration. The experimental results indicate that the time jitter of the GaAs PCSS exhibits a nonmonotonic variation in negative differential mobility (NDM) region. All of these time jitters are lower than the 4% of the rise time of the switching waveform. The optimum time jitter of ~15 ps is achieved at the onset of the NDM region. The theoretical relationship between the optical excitation parameters, the bias electric field and the time jitter of the GaAs PCSS are built up. The nonmonotonic behavior of the time jitter with electric field is attributed to the instability of the relative fluctuation of drift velocity caused by inter-valley transition of carriers in GaAs.
关键词： inter-valley transition of carriers,photoconductive semiconductor switches,gallium arsenide (GaAs),negative differential mobility (NDM),time jitter
更新于2025-09-04 15:30:14
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Intermixed Superlattices
摘要： The enhancement of stimulated Raman scattering (SRS) with a GaAs/AlAs intermixed superlattice that works as a χ (3)-quasi-phase-matched structure is studied, where such Kerr-induced effects as four-wave mixing (FWM), self-phase-modulation (SPM), cross-phase-modulation (XPM), and two-photon absorption (TPA) are included. In particular, the efficiency of anti-Stokes generation is enhanced here; anti-Stokes generation inherently has an extremely small efficiency due to a phase mismatch in the interaction of the pump, Stokes, and anti-Stokes waves (while the efficiency of Stokes generation is sufficiently large because of no such phase mismatch). The superlattice enhances the anti-Stokes efficiency up to the order of 103 when compared with that without the superlattice, particularly at a small pump intensity. In this enhancement, it is seen that there is an efficiency boost via simultaneous FWM. In this situation, it is shown how much SPM and XPM degrade the efficiency enhancement. Furthermore, an optimal superlattice length is identified that provides the highest efficiency. The degradation of the efficiency at the optimized length due to TPA is also analyzed. Finally, to gain more anti-Stokes efficiency (or control the sizes of the Stokes and anti-Stokes efficiencies), a photonic-band-gap cavity structure is proposed.
关键词： anti-Stokes generation,nonlinear optics,quasi-phase-matching,GaAs/AlAs superlattice,stimulated Raman scattering
更新于2025-09-04 15:30:14
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In <sub/>0.49</sub> Ga <sub/>0.51</sub> P/GaAs heterojunction bipolar transistors (HBTs) on 200 mm Si substrates: Effects of base thickness, base and sub-collector doping concentrations
摘要： We report performance of InGaP/GaAs heterojunction bipolar transistors (HBTs) fabricated on epitaxial films directly grown onto 200 mm silicon (Si) substrates using a thin 100% germanium (Ge) buffer layer. Both buffer layer and device layers were grown epitaxially using metalorganic chemical vapor deposition (MOCVD). With the assistance of numerical simulation, we were able to achieve high performance GaAs HBTs with DC current gain of ～100 through optimizing the base doping concentration (C-doped, ～ 1.9×1019/cm3), base layer thickness (～55 nm), and the sub-collector doping concentration (Te-doped, > 5×1018/cm3). The breakdown voltage at base (BV ceo) of higher than 9.43 V was realized with variation of < 3% across the 200 mm wafer. These results could enable applications such as power amplifiers for mobile phone handsets and monolithic integration of HBTs with standard Si-CMOS transistors on a common Si platform.
关键词： InGaP/GaAs heterojunction bipolar transistors,base doping concentrations,base thickness,Si substrates,HBTs,sub-collector doping concentrations
更新于2025-09-04 15:30:14