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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Antimonide Based Infrared Detectors for Remote Sensing
摘要： Infrared imaging (3‐25 microns) has been an important technological tool for the past 60 years since the first report of infrared detectors in 1950s. There has been a dramatic progress in the development of antimonide based detectors and low power electronic devices in the past decade with new materials like InAsSb, InAs/GaSb superlattices and InAs/InAsSb superlattices demonstrating very good performance. One of the unique aspects of the 6.1A family of semiconductors (InAs, GaSb and AlSb) is the ability to engineer the bandstructure to obtain designer band‐offsets. Our group investigates fundamental challenges in antimonide based infrared detectors and explores new avenues for next generation infrared detectors, arrays and imagers. The proposed technology has relevance for active and passive imaging for remote sensing applications. In this presentation, I will describe the material science and device physics of the antimonide systems. I will also discuss the challenges in these systems including the identification of defects that limit the performance of the detector. The use of 'unipolar barrier engineering' to realize high performance infrared detectors and focal plane arrays will be discussed. We are currently investigating low excess noise avalanche photodiodes (APDs) using superlattices. This has very important applications in remote sensing as there are two essential trade offs. The first is the conventional speed‐sensitivity trade off that limits the gain‐bandwidth product and the user has to decide the appropriate detector that meets their system requirement. The other trade‐off relates the sensitivity with the dynamic range. Researchers have used elegant approaches with the use of two detectors to achieve a high sensitivity and large dynamic range.
关键词： antimonide,remote sensing,superlattices,infrared detectors,avalanche photodiodes
更新于2025-09-09 09:28:46
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Surface induced charge transfer in CuxIn2-xS3 nanostructures and their enhanced photoelectronic and photocatalytic performance
摘要： Multi-functional semiconducting nanostructures are gaining popularity for application in photoelectronics, energy storage devices and also in industrial and environmental remediation functions. In this regard, CuxIn2-xS3 nanostructures were investigated in detail for their photoelectrical and photocatalytic performance. Their physico-chemical characteristics were at first studied using X-ray diffraction, Raman, UV–vis absorbance, X-ray photoelectron spectroscopy and high resolution electron microscopic tools. CuxIn2-xS3 based flip chip Schottky diodes were demonstrated to attest their improved conductivity and enhanced photoelectrical performance. The photo switching capabilities of a type II p-n CdTe/CuxIn2-xS3 heterojunction was also investigated. In both the device configurations, the current-voltage (I-V) characteristics revealed the forward current and rectification ratio to improve under lower threshold voltages. The time-dependent photoresponse characteristics affirmed the stability of diodes, augmenting the improved/effective separation of photo generated electron hole pairs under illumination. Additionally, the photocatalytic performances of CuxIn2-xS3 nanostructures were inferred under visible light conditions through effective remediation of methylene blue (MB) dye molecules. The obtained results infer the Cu interaction in tetragonal lattice of CuxIn2-xS3 to promote the surface induced charge transfer mechanism in respective nanostructures, thereby enhancing their photoelectronic and photocatalytic functionalities.
关键词： Nanostructures,Photodiodes,Semiconductors,Photocatalysis
更新于2025-09-09 09:28:46
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Design of Bias-Free Operational Uni-traveling-Carrier Photodiodes by Transient Simulation for High-power Pulsed Millimeter-Wave Signal Generation in the Sub-THz Regime
摘要： In this paper, bias-free operational uni-traveling-carrier photodiodes (UTC-PDs) for high-power pulsed millimeter-wave signal generation in the sub-terahertz regime are designed and investigated. The reliability of the physics-based transient simulation is first demonstrated by comparing with reported experimental results. Then, the epitaxial layers are analyzed and optimized through transient simulation for bias-free operation and high-power pulsed millimeter-wave signal generation. The performance between original and optimal structure is compared under excitation of pulse train and sinusoidal optical signals. The results show that the peak output power of the modified UTC-PD under 100-GHz, 200-GHz, and 312.5-GHz pulse train excitation is 4.685 dBm, 1.128 dBm, and ? 4.653 dBm, improved by 2.05 dB, 5.15 dB, and 9.36 dB, respectively.
关键词： Bias-free,Optical communication,Millimeter-wave,Transient simulation,Terahertz communications,Sub-terahertz,Uni-traveling-carrier photodiodes (UTC-PD)
更新于2025-09-09 09:28:46
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Wireless, battery-free, flexible, miniaturized dosimeters monitor exposure to solar radiation and to light for phototherapy
摘要： Exposure to electromagnetic radiation can have a profound impact on human health. Ultraviolet (UV) radiation from the sun causes skin cancer. Blue light affects the body’s circadian melatonin rhythm. At the same time, electromagnetic radiation in controlled quantities has beneficial use. UV light treats various inflammatory skin conditions, and blue light phototherapy is the standard of care for neonatal jaundice. Although quantitative measurements of exposure in these contexts are important, current systems have limited applicability outside of laboratories because of an unfavorable set of factors in bulk, weight, cost, and accuracy. We present optical metrology approaches, optoelectronic designs, and wireless modes of operation that serve as the basis for miniature, low-cost, and battery-free devices for precise dosimetry at multiple wavelengths. These platforms use a system on a chip with near-field communication functionality, a radio frequency antenna, photodiodes, supercapacitors, and a transistor to exploit a continuous accumulation mechanism for measurement. Experimental and computational studies of the individual components, the collective systems, and the performance parameters highlight the operating principles and design considerations. Evaluations on human participants monitored solar UV exposure during outdoor activities, captured instantaneous and cumulative exposure during blue light phototherapy in neonatal intensive care units, and tracked light illumination for seasonal affective disorder phototherapy. Versatile applications of this dosimetry platform provide means for consumers and medical providers to modulate light exposure across the electromagnetic spectrum in a way that can both reduce risks in the context of excessive exposure and optimize benefits in the context of phototherapy.
关键词： miniaturized dosimeters,phototherapy,UV,flexible,NFC,battery-free,solar radiation,blue light,wireless,photodiodes
更新于2025-09-09 09:28:46
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Excess Loss in Homodyne Detection Originating from Distributed Photocarrier Generation in Photodiodes
摘要： The distributed absorption of photons in photodiodes induces an excess noise in continuous-wave photodetection above the transit-time roll-off frequency. We show that it can be treated as a frequency-dependent excess optical loss in homodyne detection. This places a limit on the bandwidth of high-accuracy homodyne detection, even if an ideal photodetector circuit is available. We experimentally evaluate the excess loss in two ways: a comparison of signal gain and shot-noise gain of one-port homodyne detection and a balanced homodyne detection of squeezed light at a 500-MHz sideband. These results agree with an analytic expression we develop, where the randomness of the photoabsorption is directly modeled by an intrusion of vacuum field. At 500 MHz, we estimate the excess loss at 14% for a Si photodiode with 860-nm incident light, while the numerical simulation predicts much smaller excess loss in (In, Ga)As photodiodes with 1550 nm light.
关键词： squeezed light,photodiodes,excess noise,homodyne detection,quantum measurement
更新于2025-09-09 09:28:46
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InGaAs-GaAs Nanowire Avalanche Photodiodes Toward Single Photon Detection in Free-Running Mode
摘要： Single photon detection at near-infrared (NIR) wavelengths is critical for light detection and ranging (LiDAR) systems used in imaging technologies such as autonomous vehicle trackers and atmospheric remote sensing. Portable, high-performance LiDAR relies on silicon-based single-photon avalanche diodes (SPADs) due to their extremely low dark count rate (DCR) and afterpulsing probability, but their operation wavelengths are typically limited up to 905 nm. Although InGaAs-InP SPADs offer an alternative platform to extend the operation wavelengths to eye-safe ranges, their high DCR and afterpulsing severely limit their commercial applications. Here we propose a new selective absorption and multiplication avalanche photodiode (SAM-APD) platform composed of vertical InGaAs-GaAs nanowire arrays for single photon detection. Among a total of 4400 nanowires constituting one photodiode, each avalanche event is confined in a single nanowire, which means that the avalanche volume and the number of filled traps can be drastically reduced in our approach. This leads to an extremely small afterpulsing probability compared with conventional InGaAs-based SPADs and enables operation in free-running mode. We show DCR below 10 Hz, due to reduced fill factor, with photon count rates of 7.8 MHz and timing jitter less than 113 ps, which suggest that nanowire-based NIR focal plane arrays for single photon detection can be designed without active quenching circuitry that severely restricts pixel density and portability in NIR commercial SPADs. Therefore, the proposed work based on vertical nanowires provides a new degree of freedom in designing avalanche photodetectors and could be a stepping stone for high-performance InGaAs SPADs.
关键词： free-running mode,InGaAs-GaAs,single photon detection,avalanche photodiodes,near-infrared,nanowires
更新于2025-09-09 09:28:46
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Solution Processable P3HT/CdS Photodiodes and Their Electrical Characterization
摘要： In this work we apply simple layer solution deposition methods for the assembling of CdS/P3HT (poly(3-hexylthiophene)) p-n heterostructures and analyzed their photodetection properties in the visible optical range. The CdS-n layers were deposited on ITO-coated glass substrates by the chemical bath method employing an ammonia-free recipe. The P3HT-p layers were deposited on the CdS/ITO/glass substrates by the casting method from solution by dissolving P3HT in chloroform. As the back electrodes, to complete the p-n heterostructures, carbon (graphite) was used. The electrical properties of the assembled CdS/P3HT hybrid photodiodes in dark and under illumination at several intensities, in the 0-100 mW/cm2 interval, were analyzed from current density versus voltage (J-V) measurements, in the -5V to 5V bias voltage range. From these measurements, the photosensitivity of the photodiodes as a function of bias voltage was determined as 370 mA/W. The response of the photodiodes as a function of illumination intensity was determined from transient photocurrent measurements.
关键词： solution growth,hybrid photodiodes,chemical deposition,photosensors
更新于2025-09-04 15:30:14
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The Measuring System for the Thomson Scattering Diagnostics of the GOL-3 and GDT Facilities
摘要： The measuring system for Thomson scattering diagnostics of the GOL-3 and GDT facilities at the Budker Institute of Nuclear Physics is described. The system has a modular architecture and is based on eight-channel measuring subsystems, including photodetectors, two-channel recorders (ADC12500), synchronization modules, and the Ethernet/UART communication channel adapter. The photodetectors are based on avalanche photodiodes and are operable in the frequency range of 0–50 MHz. The ADC12500 recorders are used to measure scattering signals with a duration of ~20–30 ns at a sampling rate of to 500 MHz and an amplitude resolution of 12 bits and accumulate data in a buffer memory with a capacity as large as 2 MB.
关键词： ADC12500,avalanche photodiodes,GDT,measuring system,Thomson scattering diagnostics,GOL-3
更新于2025-09-04 15:30:14
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Strain effect on band structure of InAlAs digital alloy
摘要： Recently, InAlAs digital alloys have been shown to exhibit unique electronic dispersion properties, which can be used to make low-noise avalanche photodiodes. In this paper, the strain effect is analyzed for its impact on the band structure of the InAlAs digital alloy. Simulation using a tight binding model that includes the strain effect yields bandgap energies that are consistent with experimental results. The bandgap would be larger without strain. In addition, a positive relationship has been found between minigaps of the InAlAs digital alloy and the band offset between bulk InAs and AlAs at the same position in k-space.
关键词： InAlAs digital alloy,avalanche photodiodes,band structure,minigaps,strain effect
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