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Photodetecting Heterostructures from Graphene and Encapsulated Colloidal Quantum Dot Films
摘要： Heterostructure devices consisting of graphene and colloidal quantum dots (QDs) have been remarkably successful as photodetectors and have opened the door to technological applications based on the combination of these low-dimensional materials. This work explores the photodetection properties of a heterostructure consisting of a graphene field effect transistor covered by a film of silica-encapsulated colloidal QDs. Defects at the surface of the silica shell trap optically excited charge carriers, which simultaneously enables photodetection via two mechanisms: photogating, resulting in a net p-doping of the device, and Coulombic scattering of charge carriers in the graphene, producing an overall decrease in the current magnitude.
关键词： heterostructures,photogating,graphene,Coulombic scattering,colloidal quantum dots,photodetectors
更新于2025-09-11 14:15:04
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Variation of the photoluminescence spectrum of InAs/GaAs heterostructures grown by ion-beam deposition
摘要： This work reports on an experimental investigation of the influence of vertical stacking of quantum dots, the thickness of GaAs potential barriers, and their isovalent doping with bismuth on the photoluminescence properties of InAs/GaAs heterostructures. The experimental samples were grown by ion-beam deposition. We showed that using three vertically stacked layers of InAs quantum dots separated by thin GaAs barrier layers was accompanied by a red-shift of the photoluminescence peak of InAs/GaAs heterostructures. An increase in the thickness of the GaAs barrier layers was accompanied by a blue shift of the photoluminescence peak. The effect of isovalent Bi doping of the GaAs barrier layers on the structural and optical properties of the InAs/GaAs heterostructures was investigated. It was found that the Bi content up to 4.96 atom % in GaAs decreases the density of InAs quantum dots from 1.53 × 1010 to 0.93 × 1010 cm?2. In addition, the average lateral size of the InAs quantum dots increased from 14 to 20 nm, due to an increase in the surface diffusion of In. It is shown that isovalent doping of GaAs potential barriers by bismuth was accompanied by a red-shift of the photoluminescence peak of InAs quantum dots of 121 meV.
关键词： photoluminescence,semiconductors,quantum dot,ion-beam deposition,nanoheterostructures,infrared photodetectors
更新于2025-09-10 09:29:36
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Position Sensing and High Bandwidth Data Communication using Impact Ionization Engineered APD Arrays
摘要： Position sensing and high bandwidth data reception are functions typically performed by two separate detectors in conventional free space optical communication systems. In this letter, we report low excess noise, impact ionization engineered InAlAs/InGaAs avalanche photodiode arrays that can perform both functions simultaneously.
关键词： position sensitive detectors,Avalanche photodiodes,free-space optical communication,photodetectors
更新于2025-09-10 09:29:36
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Scalable Graphene-on-Organometal Halide Perovskite Heterostructure Fabricated by Dry Transfer
摘要： Graphene, a single layer conductor, can be combined with other functional materials for building efficient optoelectronic devices. However, transferring large-area graphene onto another material often involves dipping the material into water and other solvents. This process is incompatible with water-sensitive materials such as organometal halide perovskites. Here, a dry method is used and succeeded, for the first time, in stacking centimeter-sized graphene directly onto methylammonium lead iodide thin films without exposing the perovskite film to any liquid. Photoemission spectroscopy and nanosecond time-resolved photoelectrical measurement show that the graphene/perovskite interface does not contain significant amount of contaminants and sustain efficient interfacial electron transfer. The use of this method in fabricating graphene-on-perovskite photodetectors is further demonstrated. Besides a better photoresponsivity compared to detectors fabricated by the conventional perovskite-on-graphene structure, this dry transfer method provides a scalable pathway to incorporate graphene in multilayer devices based on water-sensitive materials.
关键词： photodetectors,interfaces,organometal halide perovskite,graphene,charge transfer
更新于2025-09-10 09:29:36
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Plasmon induced thermoelectric effect in graphene
摘要： Graphene has emerged as a promising material for optoelectronics due to its potential for ultrafast and broad-band photodetection. The photoresponse of graphene junctions is characterized by two competing photocurrent generation mechanisms: a conventional photovoltaic effect and a more dominant hot-carrier-assisted photothermoelectric (PTE) effect. The PTE effect is understood to rely on variations in the Seebeck coefficient through the graphene doping profile. A second PTE effect can occur across a homogeneous graphene channel in the presence of an electronic temperature gradient. Here, we study the latter effect facilitated by strongly localised plasmonic heating of graphene carriers in the presence of nanostructured electrical contacts resulting in electronic temperatures of the order of 2000 K. At certain conditions, the plasmon-induced PTE photocurrent contribution can be isolated. In this regime, the device effectively operates as a sensitive electronic thermometer and as such represents an enabling technology for development of hot carrier based plasmonic devices.
关键词： Photothermoelectric effect,Graphene,Plasmonics,Photodetectors,Hot carriers
更新于2025-09-10 09:29:36
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Photogating and high gain in ReS <sub/>2</sub> field-effect transistors
摘要： Two-dimensional layered transition metal dichalcogenides have shown much promise due to their remarkable electro-optical properties and potential use as photodetectors. We observed photogating in our few-layered (3–4 layers) ReS2 field-effect transistors (FETs) in which varying the incident optical power shifted the FETs’ threshold voltage. The photogating effect produced a significant gain in the electrical response of the FETs to incident light as measured by the responsivity (R) and external quantum efficiency (EQE). We obtained a maximum R of 45 A/W corresponding to an EQE of ～10 500% in a four-terminal measurement of the photoconductivity in the ON-state. We attribute both the photogating and the observed gain to the influence of charge traps. An estimate of the device gain based on our observations is calculated to be 5 × 104. Published by AIP Publishing.
关键词： photodetectors,high gain,charge traps,ReS2,field-effect transistors,photogating
更新于2025-09-10 09:29:36
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Effects of barrier energy offset and gradient in extended wavelength infrared detectors
摘要： The extended wavelength infrared photodetectors are new class of III-V semiconductor heterojunction-based photodetectors that can detect incoming radiation with an energy significantly smaller than the minimum energy gap (Δ) at the heterojunction interface. Architecture of these photodetectors include a barrier-emitter-barrier epilayers sandwiched between highly doped ohmic top and bottom contact layers. An energy offset (????) between the barriers is necessary for the extended wavelength photodetection. In this work, we study the performance of extended wavelength infrared photodetectors with varying ???? and gradient of the potential barrier. Results indicate that the extended wavelength threshold varied slightly with varying both the gradient and offset. Spectral responsivity, however, increased with the increasing offset and decreased with increasing gradient.
关键词： Extended wavelength infrared photodetectors,III-V semiconductors,GaAs/AlGaAs heterostructures
更新于2025-09-09 09:28:46
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anda?Barrel Time-of-Flight detector
摘要： The Barrel-Time-of-Flight detector is one of the outer layers in the multi-layer design of the ˉPanda target spectrometer, covering a polar angle region of 22?<θlab<150?. ˉPanda, which is being built at the FAIR facility, will use cooled antiprotons on a Hydrogen or nuclei target, to study a variety of topics in hadron physics. The detector is a scintillating tile hodoscope with an SiPM readout. A single unit consists of a 90×30×5mm3 fast plastic scintillator tile and 3×3mm2 SiPM photo sensors on both ends. Four SiPMs are connected in series to overcome the limited sensor size of a single SiPM sensor and to improve the time resolution drastically (100ps to 50ps). While the ˉPanda experiment is equipped with DIRC detectors for PID of faster particles, the Barrel TOF complements the setup by providing additional PID information with a π/K separation of 4 sigma up to the Cherenkov threshold.
关键词： PID,Photodetectors
更新于2025-09-09 09:28:46
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Gallium Oxide || Growth, properties, and applications of β-Ga2O3 nanostructures
摘要： This chapter provided a brief overview for β-Ga2O3 nanostructures from a growth aspect to device applications. The outstanding properties of β-Ga2O3 such as large bandgap, high breakdown field, thermal and chemical stability, along with advantageous properties due to its nanostructures morphology such as large surface-to-volume ratio, fewer defects, and less strain makes it a potential material for development of high-performance nanoscale devices. β-Ga2O3 nanostructures have shown great promise for nanoscale devices such as deep-UV photodetectors, gas sensors, and FETs. In addition, functional nanowires based on β-Ga2O3 nanostructures can also be utilized for establishing the nanoscale device platform.
关键词： device applications,photodetectors,FETs,β-Ga2O3 nanostructures,gas sensors,growth techniques
更新于2025-09-09 09:28:46
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Gallium Oxide || Radiation damage in Ga2O3
摘要： β-Ga2O3 has a large bandgap of approximately 4.9 eV and an estimated critical electric field (EC) strength of 8 MV/cm. The large bandgap of β-Ga2O3 allows high-temperature device operation and this large critical field allows high-voltage operation (relative to maximum breakdown) and the most common device structure reported to date has been Schottky rectifiers. This material also has potential in devices with low power loss during high-frequency switching in the GHz regime. Similarly, Ga2O3-based photodetectors are attracting interest for their promise as truly solar-blind deep ultraviolet (UV) photodetectors exhibiting cut-off wavelengths below 280 nm. These would have applications in detection of UV wavelengths for military applications, air purification, space communication, ozone-layer monitoring, and flame sensing.
关键词： β-Ga2O3,photodetectors,radiation damage,Schottky rectifiers,wide bandgap semiconductors
更新于2025-09-09 09:28:46