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Fabrication and characterization of sensitive vertical P-i-N germanium photodiodes as infrared detectors
摘要： Germanium on silicon P-i-N photodetectors fabricated using standard CMOS tools are now successfully used as uncooled detectors in the near-infrared (NIR), which extends from 0.75 to 1.4 μm and in the short-wave infrared (SWIR), which extends from 1.4 to 3 μm. They feature a remarkably high responsivity up to 1550 nm and a low dark current when they are operated at reverse biases. The aim is to achieve a very low dark current density and a high responsivity with a small Germanium photodiode pitch. In this paper we discuss the fabrication and the characterization of vertical P-i-N photodiodes with the epitaxy of Germanium on Silicon. The Germanium epilayer is a 1.3 μm thick Ge ?lm with a bottom Ge layer P-type doped with boron at 1019 cm?3 and a top Ge layer N-type doped with phosphorus at 1020 cm?3. Secondary ion mass spectroscopy was used to assess the doping level of the Phosphorus doped N?+?region. The strain in the Germanium epilayer on Silicon substrate was investigated. It was tensile, with a value around +0.15% from x-ray diffraction (XRD), in good agreement with a +0.12% value from Raman spectroscopy. In this paper, we focus on P-i-N photodiodes with a circular shape and a diameter of 10 μm. Electrical characterizations were performed in dark and under NIR-SWIR radiation (1310 nm, 1550 nm), with very low dark current of 0.45 nA and enhanced photocurrent at ?1 V. The external responsivities were measured at 0.275 and 0.133 A W?1 for 1310 nm and 1550 nm, respectively. Finally, internal quantum ef?ciencies of the fabricated vertical P-i-N photodiodes were extracted at 66% and 52% at 1310 nm and 1550 nm, respectively, in good agreement with TCAD simulations. Finally, a measurement of the noise in dark conditions is presented.
关键词： infrared detectors,photodiodes,strain,germanium
更新于2025-09-23 15:19:57
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Higha??Accuracy Photoplethysmography Array Using Neara??Infrared Organic Photodiodes with Ultralow Dark Current
摘要： Reflectance oximeters based on organic photodiode (OPD) arrays offer the potential to map blood pulsation and oxygenation via photoplethysmography (PPG) over a large area and beyond the traditional sensing locations. Here, an organic reflectance PPG array based on 16 × 16 OPD pixels is developed. The individual pixels exhibit near-infrared sensitivity up to ≈950 nm and low dark current density in the order of 10?6 mA cm?2. This results in high-quality PPG signals. Analysis of the full PPG waveform yields insight on the artery stiffness and the quality of blood circulation, demonstrating the potential of these arrays beyond pulse oximetry and heart-rate calculation.
关键词： photoplethysmography,organic photodiodes,bulk heterojunction,heartbeat,pulse oximetry
更新于2025-09-23 15:19:57
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High-speed III-V based avalanche photodiodes for optical communicationsa??the forefront and expanding applications
摘要： Avalanche photodiodes (APDs), i.e., semiconductor devices, which convert and amplify optical signals into electrical signals, are used for optical communications and for imaging and medical applications. The major requirements for APDs in optical communications are high-speed operation for high data rates and high-sensitivity operation for extending the transmission reach. This paper overviews the achievements of high-speed APDs for 100-Gbit/s optical communications, focusing on III-V material systems, which are advantageous in terms of band engineering. The outlook for APDs in future optical communications is also described.
关键词： high-speed operation,high-sensitivity operation,III-V material systems,optical communications,Avalanche photodiodes
更新于2025-09-23 15:19:57
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A Data-Driven Home Energy Scheduling Strategy Under the Uncertainty in Photovoltaic Generations
摘要： We report the fabrication of InAs planar avalanche photodiodes (APDs) using Be ion implantation. The planar APDs have a low background doping of 2 × 1014 cm?3 and large depletion widths approaching 8 μm. The thick depletion width enabled a gain of 330 to be achieved at ?26 V at 200 K without inducing a significant tunneling current. No edge breakdown was observed within the APDs. The surface leakage current was found to be low with a gain normalized dark current density of 400 μAcm?2 at ?20 V at 200 K.
关键词： Avalanche photodiodes,ion implantation,infrared detectors
更新于2025-09-23 15:19:57
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Low Dark Current 1.55 Micrometer InAs Quantum Dash Waveguide Photodiodes
摘要： Photodiodes and integrated optical receivers operating at 1.55 micrometer (μm) wavelength are crucial for long-haul communication and data transfer systems. In this paper, we report C-band InAs quantum dash (Qdash) waveguide photodiodes (PDs) with a record-low dark current of 5 pA, a responsivity of 0.26 A/W at 1.55 μm, and open eye diagrams up to 10 Gb/s. These Qdash-based PDs leverage the same epitaxial layers and processing steps as Qdash lasers and can thus be integrated with laser sources for power monitors or amplifiers for pre-amplified receivers, manifesting themselves as a promising alternative to their InGaAs and Ge counterparts in low-power optical communication links.
关键词： C-band communication,photodiodes,optoelectronics,low dark-current,quantum dashes
更新于2025-09-23 15:19:57
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Passive Quenching Electronics for Geiger Mode 4H-SiC Avalanche Photodiodes
摘要： We design and fabricate 4H-SiC UV avalanche photodiodes (APDs) with positive beveled mesa, which exhibit low leakage current and high avalanche gain when working in the Geiger mode. The single photon counting performance of the SiC APDs is studied by using a passive-quenching circuit. A new method to determine the exact breakdown voltage of the APD is proposed based on the initial emergence of photon count pulses. The photon count rate and dark count rate of the APD are also evaluated as a function of quenching resistance.
关键词： 4H-SiC,single photon counting,passive quenching,Geiger mode,avalanche photodiodes,breakdown voltage
更新于2025-09-19 17:15:36
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AsP/InSe Van der Waals Tunneling Heterojunctions with Ultrahigh Reverse Rectification Ratio and High Photosensitivity
摘要： Van der Waals heterojunctions made of 2D materials offer competitive opportunities in designing and achieving multifunctional and high-performance electronic and optoelectronic devices. However, due to the significant reverse tunneling current in such thin p–n junctions, a low rectification ratio along with a large reverse current is often inevitable for the heterojunctions. Here, a vertically stacked van der Waals heterojunction (vdWH) tunneling device is reported consisting of black arsenic phosphorus (AsP) and indium selenide (InSe), which shows a record high reverse rectification ratio exceeding 107 along with an unusual ultralow forward current below picoampere and a high current on/off ratio over 108 simultaneously at room temperature under the proper band alignment design of both the Schottky junction and the heterojunction. Therefore, the vdWH tunneling device can function as an ultrasensitive photodetector with an ultrahigh light on/off ratio of 1 × 107, a comparable responsivity of around 1 A W?1, and a high detectivity over 1 × 1012 Jones in the visible wavelength range. Furthermore, the device exhibits a clear photovoltaic effect and shows a spectral detection capability up to 1550 nm. The work sheds light on developing future electronic and optoelectronic multifunctional devices based on the van der Waals integration of 2D materials with designed band alignment.
关键词： van der Waals heterojunctions,backward diodes,rectification,photodiodes,tunneling
更新于2025-09-19 17:15:36
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Bifunctional Etalon-Electrode to Realize High Performance Color Filter Free Image Sensor
摘要： Organic photodiodes (OPDs), based on organic semiconductors with high absorption coefficients for visible light, are emerging as potential candidates for replacing silicon photodiodes in image sensors, particularly due to the possibility of realizing a thin thickness and exclusion of color filters, both of which can contribute to a dramatically enhanced degree of integration for image sensors. Despite years of research, techniques have not yet been developed that allow the OPD itself to have color selectivity while maintaining a thin (<1 μm) OPD thickness, in combination with a sufficiently high detectivity (>1012 cm?Hz0.5/W). To solve this issue, we introduce a concept of 'etalon-electrode', which can perform the function of electrode, and simultaneously the function of selective wavelength transparency. A strategically designed OPD architecture consisting of an etalon-electrode, a panchromatic organic active layer, and a counter electrode displays well-defined narrowband R-/G-/B-selective detectivity spectra depending on precision-adjusted thickness composition of the etalon-electrode. While a thin thickness of OPD is preserved at less than 800 nm including electrodes, active layer and other buffer layers for all R-/G-/B-selective OPDs, high average detectivity values over 1012 cm?Hz0.5/W are demonstrated. Furthermore, the characteristic of imparting color selectivity by the etalon-electrode enables a more facile full color patterning, such that a prototype of a 10×10 image sensor with a pixel pitch of 500 μm is realized, resulting in accurate picturing of a well-defined full color image.
关键词： high detectivity,organic photodiodes,etalon-electrodes,full-color imaging,color filter free,image sensor,wavelength selectivity
更新于2025-09-19 17:15:36
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[IEEE 2019 International Topical Meeting on Microwave Photonics (MWP) - Ottawa, ON, Canada (2019.10.7-2019.10.10)] 2019 International Topical Meeting on Microwave Photonics (MWP) - 300 GHz Photonic Self-Mixing Imaging-System with vertical illuminated Triple-Transit-Region Photodiode Terahertz Emitters
摘要： In this paper, we report a phase-sensitive photonic THz two-tone self-mixing imaging system, comprising a self-developed vertical illuminated triple transit region photodiode (TTR-PD) and a commercial square law Schottky barrier diode as THz emitter and THz detector, respectively. Using the two-tone self-mixing approach, the phase information of a device-under-test can be extracted by down-mixing two THz signals inside the SBD, whereas the phase information remains in the output signal. The THz tones are generated by two free-running lasers and the TTR-PD, while one optical signal is externally modulated for double sideband carrier suppression. By means of the self-mixing, the phase noises of the free running lasers are canceled out. Using a second PD for the trigger, lock-in detection allows fast imaging speed, only limited by the integration constant. Beside the imaging system, we present the characteristics of the used vertically illuminated terahertz triple transit region photodiodes with thin depletion zone and small active areas. Numerical analysis by energy-balance model based TCAD simulations show transit-time limitations over 200 GHz, due to the electron field management within the active photodiode layers and the resulting high electron velocities. Therefore, the fabricated TTR-PDs show a flat ±2 dB frequency response within the frequency range from 225 GHz to 305 GHz. By employing the proposed photonic two-tone imaging system with the fabricated TTR-PDs, amplitude and phase difference vector images are taken at 299.5 GHz and 300.5 GHz. Metal and acrylic glass items inside a paper envelope are clearly visible, which demonstrates the potential of the system.
关键词： energy balance,self-mixing,TCAD,Terahertz spectroscopy,terahertz imaging,terahertz photodiodes
更新于2025-09-19 17:13:59
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Industrial Applications of Nanomaterials || Nanomaterials-based UV photodetectors
摘要： Photodetectors are essential elements applied in video imaging, optical communications, biomedical imaging, security, night-vision, gas sensing, and motion detection, which possess the ability to transform light into electrical signals precisely. As the scale and diversity of application areas are growing, the need for innovative photodetection platform technologies with higher performance in terms of speed, efficiency or wavelength range, as well as material flexibility, transparency, and complementary metal-oxide-semiconductor (CMOS) integrability, is becoming more critical. In the past decades, extensive efforts have been devoted to explore the next generation of photodetector materials, such as In2Te3, ZnO, and GaN, with low noise, high photosensitivity, and good stability. However, many of these novel photodetector materials still suffer from limited photocurrent and photoresponse speed.
关键词： Nanomaterials,Schottky contacts,photoconductive gain,photodetection mechanism,photoresistors,linear dynamic range,responsivity,external quantum efficiency,photodiodes,specific detectivity,UV photodetectors
更新于2025-09-19 17:13:59