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- 2018
- Dual Material Gate (DMG)
- Vertical TFET
- Single Material Gate(SMG)
- Band-to-band tunneling (BTBT)
- Electronic Science and Technology
- National Institute of Technology Silchar
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High performance n-type vertical organic phototransistors
摘要： In this manuscript, a solution-processed n-type organic phototransistor based on vertical structure thin-film transistors was proposed. Due to the vertical structure and short channel length (≈130 nm), the transistors exhibited excellent current density (15.4 mA/cm2) with high Ion/Ioff ratio (up to 105). On account of this structure, the face-on π-π stacking of P(NDI2OD-T2) was aligned with the charge transport direction, which facilitated charge transfer from source to drain electrode. Moreover, n-type organic phototransistors based on vertical thin-film transistors were demonstrated for the first time, in which the active layer was protected by the source-drain electrodes, resulting in the improvement of the stability of the device. Due to the nanoscale channel, efficient separation of electron-hole pairs and quick charge transfer can be achieved. Hence, high-performance n-type phototransistor was obtained with responsivity of 34.8 A/W, photosensitivity of 4.78×104, detectivity of 3.95×1013 Jones and external quantum efficiency up to 1.1×104 % under 400 nm illumination with a light intensity of 200 μW cm-2, which was much better than those reported n-type organic phototransistors. This work provided a strategy for the fabrication of high performance n-type organic phototransistor, which paved the way for its future application in the next-generation organic optoelectronics.
关键词： n-type organic semiconductor,Organic phototransistors,Vertical structure,Organic thin-film transistors
更新于2025-09-19 17:15:36
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Biosensing Using Arrays of Vertical Semiconductor Nanowires: Mechanosensing and Biomarker Detection
摘要： Due to their high aspect ratio and increased surface to foot-print area, arrays of vertical semiconductor nanowires are used in numerous biological applications, such as cell transfection and biosensing. Here we focus on two specific, valuable biosensing approaches that, so far, have received relatively limited attention in terms of their potential capabilities: cellular mechanosensing and lightguiding-induced enhanced fluorescence detection. Although proposed a decade ago, these two applications for using vertical nanowire arrays have only very recently achieved significant breakthroughs, both in terms of understanding their fundamental phenomena, and in the ease of their implementation. We review the status of the field in these areas and describe significant findings and potential future directions.
关键词： mechanosensing,vertical nanowire arrays,fluorescence detection,biosensing,semiconductor nanowires
更新于2025-09-19 17:15:36
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Research on a 3D Encapsulation Technique for Capacitive MEMS Sensors Based on Through Silicon Via
摘要： A novel three-dimensional (3D) hermetic packaging technique suitable for capacitive microelectromechanical systems (MEMS) sensors is studied. The composite substrate with through silicon via (TSV) is used as the encapsulation cap fabricated by a glass-in-silicon (GIS) reflow process. In particular, the low-resistivity silicon pillars embedded in the glass cap are designed to serve as the electrical feedthrough and the fixed capacitance plate at the same time to simplify the fabrication process and improve the reliability. The fabrication process and the properties of the encapsulation cap were studied systematically. The resistance of the silicon vertical feedthrough was measured to be as low as 263.5 m?, indicating a good electrical interconnection property. Furthermore, the surface root-mean-square (RMS) roughnesses of glass and silicon were measured to be 1.12 nm and 0.814 nm, respectively, which were small enough for the final wafer bonding process. Anodic bonding between the encapsulation cap and the silicon wafer with sensing structures was conducted in a vacuum to complete the hermetic encapsulation. The proposed packaging scheme was successfully applied to a capacitive gyroscope. The quality factor of the packaged gyroscope achieved above 220,000, which was at least one order of magnitude larger than that of the unpackaged. The validity of the proposed packaging scheme could be verified. Furthermore, the packaging failure was less than 1%, which demonstrated the feasibility and reliability of the technique for high-performance MEMS vacuum packaging.
关键词： vertical interconnect,capacitive,glass reflow,MEMS,3D encapsulation
更新于2025-09-19 17:15:36
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Impact of Chirp in High-Capacity Optical Metro Networks Employing Directly-Modulated VCSELs
摘要： Directly modulated long-wavelength vertical cavity surface emitting lasers (VCSELs) are considered for the implementation of sliceable bandwidth/bitrate variable transceivers for very high capacity transmission (higher than 50 Gb/s per wavelength) in metropolitan area systems characterized by reduced cost, power consumption, and footprint. The impact of the frequency chirp measured for InP VCSELs with different kinds of design (high-bandwidth very short cavity and widely-tunable with micro electro-mechanical systems (MEMS) top mirror) is analyzed in case of discrete multitone (DMT) direct modulation in combination with 25-GHz wavelength selective switch (WSS) filtering. The maximum transmitted capacity for both dual side- and single side-band DMT modulation is evaluated as a function of the number of crossed nodes in a mesh metro network, comparing VCSEL based transmitters performance also with the case of external electro-absorption modulator use. Finally, the maximum reach achieved based on the received optical signal to noise ratio (OSNR) and the fiber span length is discussed. The results confirm the possibility to use directly-modulated long-wavelength VCSELs for the realization of sliceable bandwidth/bitrate variable transmitters targeting 50-Gb/s capacity per polarization, also in the presence of 5 crossed WSSs for reaches of hundreds of kilometers in multi-span Erbium-doped fiber amplified (EDFA) metro links supported by coherent detection.
关键词： optical communications,vertical cavity surface emitting lasers,discrete multitone,metro networks,direct modulation
更新于2025-09-19 17:15:36
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Laser Characteristics for VCSELs for 77 K and 4 K Optical Data Applications
摘要： Small-sized vertical-cavity surface-emitting laser (VCSEL) offer the possibility of very low power consumption along with high reliability for cryogenic data transfer. Cryogenic data transfer has applications in focal plane array cameras operating at 77 K, and at the lower temperature of 4 K for data extraction from superconducting circuits. A theoretical analysis is presented for 77 K and 4 K operation based on small cavity, oxide-free VCSEL sizes of 2 to 6 μm, that have been shown to operate efficiently at room temperature. Temperature dependent operation for optimally-designed VCSELs are studied by calculating the response of the laser at 77 K and 4 K to estimate their bias conditions needed to reach modulation speed for cryogenic optical links. The temperature influence is to decrease threshold for reducing temperature, and to increase differential gain for reducing temperature. The two effects predict very low bias currents for small cavity VCSELs to reach needed data speed for cryogenic optical data links. Changing the number of top-mirror pairs has also been studied to determine how cavity design impacts speed and bit energy. Our design and performance predictions paves the way for realizing highly efficient, ultra-small VCSEL arrays with applications in optical interconnects.
关键词： Vertical cavity surface emitting lasers,Cryogenics,semiconductor devices,laser physics,high speed modulation,optical data transmission
更新于2025-09-19 17:13:59
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Design of high-performance double quantum well vertical cavity transistor lasers with GRIN base region
摘要： Different confinement structures are analyzed to achieve higher optoelectronic performances for double quantum well vertical cavity transistor laser with graded index separate confinement heterostructure. Adding the drift component to the diffusion term of the current density and solving new sets of equations, modified electro-optic performances of the device is obtained. Band-gap engineering of the original structure predicts simultaneous improvements in both current gain (more than two times) and ?3 dB optical bandwidth (by 1.5 GHz). Other less critical, yet important, performance metrics including optical output power and threshold current (up to 20%) are enhanced due to applying graded layers of AlξGa1-ξAs in the base region.
关键词： Vertical cavity transistor laser,GRIN base region,Optoelectronic performance,Double quantum well,Band-gap engineering
更新于2025-09-19 17:13:59
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Room-temperature continuous-wave operation of green vertical-cavity surface-emitting lasers with a curved mirror fabricated on {20a??21} semi-polar GaN
摘要： We demonstrate a room-temperature continuous-wave operation of green vertical-cavity surface-emitting laser with a 20-μm-long cavity possessing a dielectric curved mirror formed over a {20?21} semi-polar Gallium Nitride substrate. The emission wavelength and the threshold current were 515 nm and 1.8 mA, respectively. We also confirmed that white light is generated by overlaying three prime colors of light, i.e. red, blue and green, emitted only from vertical-cavity surface-emitting lasers.
关键词： curved mirror,green emission,continuous-wave operation,semi-polar GaN,vertical-cavity surface-emitting laser
更新于2025-09-19 17:13:59
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Exploiting the Optical Reflection Matrix for OCT Signal Enhancement
摘要： Electric ?elds can be effectively used to sense, manipulate, and move particles in lab-on-a-chip devices. Nevertheless, the throughput of such devices is a critical issue, which can be effectively improved by increasing the height of the microchannels. For this purpose, vertical electrodes are needed in order to apply electrical stimuli homogeneously over the full height of the channel. In this paper, we propose different fabrication processes based on a conformal coating of 3-D SU-8 structures with metal layers, de?ning vertical electrodes in micro?uidic channels with high aspect ratio and uniform coating of the vertical sidewalls. We describe two different strategies to achieve the patterning of connection lines inside the gaps of the pillar electrodes—one based on liftoff and the other based on dry ?lm resist. We show how the liftoff approach allows for high connection densities and high resolution of the patterning inside the 3-D electrode arrays. Moreover, we highlight how the dry ?lm process provides an ef?cient and low-cost alternative when neither high-density patterning nor high resolution is needed. Standard resistive and impedance measurements show high conductivity of the structures whose fabrication process grants standard photolithographic resolution in the de?nition of the electrode features.
关键词： vertical electrodes,microelectrode arrays,SU-8,3D microelectrodes,SU-8/PDMS bonding
更新于2025-09-19 17:13:59
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An <i>in situ</i> assembled WO <sub/>3</sub> a??TiO <sub/>2</sub> vertical heterojunction for enhanced Z-scheme photocatalytic activity
摘要： The face-to-face contact of a vertical heterojunction is beneficial to charge interaction in photocatalysis. However, constructing a vertical heterojunction with uncompromised redox ability still remains a challenge. Herein, we report the successful synthesis of a WO3–TiO2 vertical heterojunction via establishing an internal electric field across the interface. Experimental investigation and computational simulations reveal that strong electric coupling occurs at the WO3–TiO2 interface forming an internal electric field. The internal electric field induces a Z-scheme charge-carrier transfer through the heterojunction under light irradiation, which leads to effective charge separation and maintains high reaction potentials of charge-carriers. The improved photocatalytic activity of the WO3–TiO2 heterojunction is proved by enhanced generation of reactive oxygen species and accelerated Escherichia coli (E. coli) disinfection. This study provides new insights into understanding and designing Z-scheme heterogeneous photocatalysts.
关键词： vertical heterojunction,Z-scheme,E. coli disinfection,WO3–TiO2,reactive oxygen species,photocatalysis
更新于2025-09-19 17:13:59
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Recent progress on infrared photodetectors based on InAs and InAsSb nanowires
摘要： In recent years, quasi-one-dimensional semiconductor nanowires have attracted numerous research interests in the field of optoelectronic devices. Indium arsenide (InAs) nanowire, an III-V compound semiconductor structure with a narrow bandgap, shows high electron mobility and high absorption from the visible to the mid-wave infrared (MWIR), holding promise for room-temperature high-performance infrared photodetectors. Therefore, the material growth, device preparation, and performance characteristics have attracted increasing attention, enabling high sensitivity InAs nanowire photodetector from the visible to the MWIR at room temperature. This review starts by discussing the growth process of the low-dimensional structure and elementary properties of the material, such as the crystalline phase, mobility, morphology, surface states, and metal contacts. Then, three solutions, including the visible-light assisted infrared photodetection technology, the vertical nanowire array technology, and band engineering by the growth of InAsSb nanowires with increasing Sb components, are elaborated to obtain longer cut-off wavelength coverage of photodetectors. Finally, the potentials and challenges of the state-of-the-art optoelectronic technologies for InAs nanowire MWIR photodetectors are summarized and compared, and preliminary suggestions for the technical development route and prospects are presented. This review mainly delineates the research progress of material growth, device fabrication and performance characterization of InAs nanowire MWIR photodetectors, providing a reference for the development of the next-generation high-performance photodetectors over a wide spectrum range.
关键词： nanowire,vertical array,InAsSb,mid-wave infrared photodetector,InAs
更新于2025-09-19 17:13:59