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Efficient Alla??Optical Plasmonic Modulators with Atomically Thin Van Der Waals Heterostructures
摘要： All-optical modulators are attracting significant attention due to their intrinsic perspective on high-speed, low-loss, and broadband performance, which are promising to replace their electrical counterparts for future information communication technology. However, high-power consumption and large footprint remain obstacles for the prevailing nonlinear optical methods due to the weak photon–photon interaction. Here, efficient all-optical mid-infrared plasmonic waveguide and free-space modulators in atomically thin graphene-MoS2 heterostructures based on the ultrafast and efficient doping of graphene with the photogenerated carrier in the monolayer MoS2 are reported. Plasmonic modulation of 44 cm?1 is demonstrated by an LED with light intensity down to 0.15 mW cm?2, which is four orders of magnitude smaller than the prevailing graphene nonlinear all-optical modulators (≈103 mW cm?2). The ultrafast carrier transfer and recombination time of photogenerated carriers in the heterostructure may achieve ultrafast modulation of the graphene plasmon. The demonstration of the efficient all-optical mid-infrared plasmonic modulators, with chip-scale integrability and deep-sub wavelength light field confinement derived from the van der Waals heterostructures, may be an important step toward on-chip all-optical devices.
关键词： all-optical plasmonic modulators,graphene plasmon,van der Waals heterostructures,2D materials
更新于2025-09-19 17:13:59
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Spatially Controlled Lateral Heterostructures of Graphene and Transition Metal Dichalcogenides toward Atomically Thin and Multi-Functional Electronics
摘要： Edge contacts between two-dimensional (2D) materials in the in-plane direction can achieve minimal contact area and low contact resistance, producing atomically thin devices with improved performance. Specifically, lateral heterojunctions of metallic graphene and semiconducting transition metal dichalcogenides (TMDs) exhibit small Schottky barrier heights due to graphene’s low work-function. However, issues exist with fabrication of highly transparent and flexible multi-functional devices utilizing lateral heterostructures (HSs) of graphene and TMDs via spatially controlled growth. This review demonstrates growth and electronic applications of lateral HSs of graphene and TMDs, highlighting key technologies controlling wafer-scale growth of continuous films for practical applications. It deepens the understanding of the spatially controlled growth of lateral HSs using chemical vapor deposition methods, and also contribute to the applications for the scale-up of all-2D electronics with ultra-high electrical performance.
关键词： electronic applications,graphene,lateral heterostructures,chemical vapor deposition,transition metal dichalcogenides
更新于2025-09-19 17:13:59
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Graphene based plasma-wave devices for terahertz applications
摘要： Unique properties of graphene are combined to enable graphene plasmonic devices that could revolutionize the terahertz (THz) electronic technology. A high value of the carrier mobility allows us to excite resonant plasma waves. The graphene bipolar nature allows for different mechanisms of plasma wave excitation. Graphene bilayer and multilayer structures make possible improved THz device configurations. The ability of graphene to form a high quality heterostructure with h-BN, black phosphorus, and other materials systems supports advanced heterostructure devices comprised of the best properties of graphene and other emerging materials. In particular, using black phosphorus compounds for cooling electron–hole plasma in graphene could dramatically improve the conditions for THz lasing. High optical phonon energy allows for reaching higher plasma frequencies that are supported by high sheet carrier densities in graphene. Recent improvements in graphene technology combined with a better understanding of the device physics of graphene THz plasmonics and graphene plasmonic device designs hold promise to make graphene THz plasmonic technology one of the key graphene applications. Commercialization of plasmonic graphene technology is facing the same challenges as other graphene applications, which have difficulties in producing uniform large graphene layers, bilayers, and heterostructures of high quality and making good low resistance stable Ohmic contacts. The time projection for large scale graphene electronic device applications now extends into the 2030s. However, emerging graphene mass production technologies might bring commercial applications of the graphene plasmonic terahertz technology closer.
关键词： heterostructures,graphene,black phosphorus,Ohmic contacts,plasma waves,THz technology,terahertz,plasmonic devices,optical phonon energy,carrier mobility
更新于2025-09-19 17:13:59
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Interlayer Transition in a vdW Heterostructure toward Ultrahigh Detectivity Shortwave Infrared Photodetectors
摘要： Van der Waals (vdW) heterostructures of 2D atomically thin layered materials (2DLMs) provide a unique platform for constructing optoelectronic devices by staking 2D atomic sheets with unprecedented functionality and performance. A particular advantage of these vdW heterostructures is the energy band engineering of 2DLMs to achieve interlayer excitons through type-II band alignment, enabling spectral range exceeding the cutoff wavelengths of the individual atomic sheets in the 2DLM. Herein, the high performance of GaTe/InSe vdW heterostructures device is reported. Unexpectedly, this GaTe/InSe vdWs p–n junction exhibits extraordinary detectivity in a new shortwave infrared (SWIR) spectrum, which is forbidden by the respective bandgap limits for the constituent GaTe (bandgap of ≈1.70 eV in both the bulk and monolayer) and InSe (bandgap of ≈1.20–1.80 eV depending on thickness reduction from bulk to monolayer). Specifically, the uncooled SWIR detectivity is up to ≈1014 Jones at 1064 nm and ≈1012 Jones at 1550 nm, respectively. This result indicates that the 2DLM vdW heterostructures with type-II band alignment produce an interlayer exciton transition, and this advantage can offer a viable strategy for devising high-performance optoelectronics in SWIR or even longer wavelengths beyond the individual limitations of the bandgaps and heteroepitaxy of the constituent atomic layers.
关键词： interlayer transitions,2D materials,vdW heterostructures,broadband photodetectors,shortwave infrared
更新于2025-09-19 17:13:59
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Band engineering of III-nitride-based deep-ultraviolet light-emitting diodes: A review
摘要： III-nitride deep ultraviolet (DUV) light-emitting diodes (LEDs) are identified as the promising candidate for energy-efficient, environment-friendly and robust UV lighting source in the application of water/air purification, sterilization, and bio-sensing. However, the state-of-art DUV LED performance is far from satisfaction for commercialization owing to its low internal quantum efficiency, large current leakage and efficiency droop at high current injection, etc. Extensive efforts have been devoted to properly designing the band structures of such luminescent devices to enhance their output power. In this review, we summarize the recent progress on various energy band designs and engineering of DUV LEDs, with particular of interest is paid on the various approaches in band engineering of the electron-blocking layer, quantum well, quantum barrier and the implementation of many novel structures such as tunnel junctions, ultrathin quantum heterostructures to enhance their efficiency. Those inspirational approaches pave the way towards the next generation of greener and efficient UV sources for practical applications.
关键词： Quantum well,Quantum barrier,Deep ultraviolet light-emitting diode,Ultrathin quantum heterostructures,Band engineering,Electron-blocking layer,Tunnel junctions,III-nitride
更新于2025-09-19 17:13:59
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Recent Progress of Heterojunction Ultraviolet Photodetectors: Materials, Integrations, and Applications
摘要： Ultraviolet photodetectors (UV PDs) with “5S” (high sensitivity, high signal-to-noise ratio, excellent spectrum selectivity, fast speed, and great stability) have been proposed as promising optoelectronics in recent years. To realize high-performance UV PDs, heterojunctions are created to form a built-in electrical field for suppressing recombination of photogenerated carriers and promoting collection efficiency. In this progress report, the fundamental components of heterojunctions including UV response semiconductors and other materials functionalized with unique effects are discussed. Then, strategies of building PDs with lattice-matched heterojunctions, van der Waals heterostructures, and other heterojunctions are summarized. Finally, several applications based on heterojunction/heterostructure UV PDs are discussed, compromising flexible photodetectors, logic gates, and image sensors. This work draws an outline of diverse materials as well as basic assembly methods applied in heterojunction/heterostructure UV PDs, which will help to bring about new possibilities and call for more efforts to unleash the potential of heterojunctions.
关键词： ultraviolet photodetectors,heterojunctions,semiconductors,van der Waals heterostructures,lattice-matched heterojunctions
更新于2025-09-19 17:13:59
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Mid-infrared Polarized Emission from Black Phosphorus Light-Emitting Diodes
摘要： We demonstrate a mid-infrared light-emitting diode based on the 2D semiconductor black phosphorus (BP). The device is composed of a mechanically exfoliated BP/molybdenum disulfide heterojunction. Under forward bias, it emits polarized electroluminescence at λ = 3.68 μm, with room-temperature internal and external quantum efficiencies of ~1% and ~0.03%, respectively. In our structure, outcoupling losses are dominated by radiation towards the high refractive index substrate. The ability to tune the bandgap of BP, and consequently its emission wavelength with layer number, strain and electric field make these LEDs particularly attractive for heterointegration into mid-infrared photonic platforms.
关键词： heterostructures,2D materials,mid-infrared emitters,light-emitting diodes,Black phosphorus
更新于2025-09-19 17:13:59
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[IEEE 2019 European Space Power Conference (ESPC) - Juan-les-Pins, France (2019.9.30-2019.10.4)] 2019 European Space Power Conference (ESPC) - Performance of Solar Cell Grids based on Ag, Au, and Al for Cost-Effective Manufacturing
摘要： We report on the performance of front contact grids based on Ag, Al, and Au applied to III?V multijunction solar cells. We compare their suitability as grid metals from different perspectives, including price, mass-to-conductivity ratio, and abundance. The grid functionality was evaluated by performing charge transport experiments under simulated sunlight. The best solar cell performance was obtained for Ag contacts. On the other hand, Al and Ag provide the most cost-effective approach: when compared to Au, the cost for the grid material for equal conductivities is only about 1.1% for the Ag contacts, and 0.7% for Al.
关键词： cost-effectivity,solar cell,grid design,III?V heterostructures
更新于2025-09-19 17:13:59
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[IEEE 2019 International Conference on Optical MEMS and Nanophotonics (OMN) - Daejeon, Korea (South) (2019.7.28-2019.8.1)] 2019 International Conference on Optical MEMS and Nanophotonics (OMN) - Hybrid Dielectric Metasurfaces: From Strong Light-Matter Interaction to Extreme Nonlinearities
摘要： We experimentally demonstrate strong coupling between Mie modes of dielectric resonators in a metasurface and intersubband transitions in semiconductor quantum wells that are embedded inside the resonator. The ability to achieve such light-matter coupling creates the possibility to realize ultrathin nonlinear optical devices that are free from complex phase matching requirements and have very high nonlinear conversion efficiencies.
关键词： Rabi splitting,Intersubband transitions,Nonlinear optics,Semiconductor heterostructures,Metasurface
更新于2025-09-16 10:30:52
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Electron Population Dynamics in Optically Pumped Asymmetric Coupled Ge/SiGe Quantum Wells: Experiment and Models
摘要： n-type doped Ge quantum wells with SiGe barriers represent a promising heterostructure system for the development of radiation emitters in the terahertz range such as electrically pumped quantum cascade lasers and optically pumped quantum fountain lasers. The nonpolar lattice of Ge and SiGe provides electron–phonon scattering rates that are one order of magnitude lower than polar GaAs. We have developed a self-consistent numerical energy-balance model based on a rate equation approach which includes inelastic and elastic inter- and intra-subband scattering events and takes into account a realistic two-dimensional electron gas distribution in all the subband states of the Ge/SiGe quantum wells by considering subband-dependent electronic temperatures and chemical potentials. This full-subband model is compared here to the standard discrete-energy-level model, in which the material parameters are limited to few input values (scattering rates and radiative cross sections). To provide an experimental case study, we have epitaxially grown samples consisting of two asymmetric coupled quantum wells forming a three-level system, which we optically pump with a free electron laser. The benchmark quantity selected for model testing purposes is the saturation intensity at the 1→3 intersubband transition. The numerical quantum model prediction is in reasonable agreement with the experiments and therefore outperforms the discrete-energy-level analytical model, of which the prediction of the saturation intensity is off by a factor 3.
关键词： silicon–germanium heterostructures,intersubband photoluminescence,optical pumping,intersubband transitions,electron–phonon interaction,infrared spectroscopy,quantum wells,free electron laser,terahertz quantum cascade laser
更新于2025-09-16 10:30:52