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Zero-biased photodetectors have desirable characteristics for potentially next-generation devices, including high efficiency, rapid response, and low power operation. In particular, the detector efficiency can be improved simply by changing the electrode contact geometry or morphological structure of materials, which give unique properties such as energy band bending, photo absorbance and electric field distribution. In addition, several combinations of materials enable or disable the operation of selective wavelengths of light detection. Herein, such recent progresses in photodetector operating at zero-bias voltage are reviewed. Considering the advantages and promises of these low-power photodetectors, this review introduces various zero-bias implementations and reviews the key points. [ABSTRACT FROM AUTHOR]

Lighting and light distribution have a crucial influence on factors such as performance and occupational safety. This paper aims to create a virtual instrument (VI), developed around the Arduino Uno development platform, designed to measure the light intensity using the BPW34 sensitive silicon PIN photodiode. The reverse-biased photodiode can be used as a light detector by monitoring the current flowing through it. Coupled to a 10Kohm resistor and considering the specifications of the BPW34 model, a simple relationship is offered between lux (light intensity) and the voltage across the resistance. The virtual instrument reads this voltage and converts it to a light intensity value in Lux. There is also an alarming function if the light intensity exceeds the set value. The VI also shows basic statistics like Max, Mean, and Min light intensity values. [ABSTRACT FROM AUTHOR]

We investigate the transmission distance of a 20-Gbaud 6-mode dual-polarization QPSK transmission system using the Kramers–Kronig(KK) receiver based on the mode permutation (MP) scheme. Compared to the system without the use of MP scheme, the maximum transmission distance is increased from 460 km to 910 km and to over 1000 km via the cyclic mode permutation and the mirror-flipped mode permutation, respectively, at the KP4 forward error correction (FEC) threshold of 2. 2 × 1 0 − 4 . The required carrier signal power budget of KK receiver is also reduced. The KK receiver can detect the signal of each mode after the transmission of 1000 km with potential advantages of low cost and low power. It is shown as a competitive detection technique in medium-reach metropolitan networks. • The Kramers–Kronig(KK) receiver based on mode permutation technique performs well. • The KK receiver can reconstruct four-dimensional signals using just two photodiodes. • Mode permutation technique effectively alleviates the linear impairment of channels. • With mode permutation, the transmission limit of the KK receiver exceeds 1000 km. [ABSTRACT FROM AUTHOR]

Thermal noise sources are relevant for future gravitational wave detectors due to the foreseen increase in sensitivity, especially at frequencies below ▪. As most thermal noise sources scale with the square root of the temperature, cooling critical optical components and their suspension system is essential. This also requires a much wider range of temperature compatibility from all technology deployed in the last suspension stages, including displacement and inertial sensors. We demonstrate and characterize a setup for stable light sources and light intensity sensing for temperatures from 300 to ▪. Commercial collimators and fibers were tested to use light from stabilized laser sources in the cryogenic environment. We also investigated multiple semiconductor compositions of photodiodes and identified a solution with high and stable responsivity at ▪. • Study of the cryogenic compatibility of commercial optical components for 1550 nm. • Identification of collimators with stable light throughput from 8 to 300 K. • Investigation of different InGaAs photodiode semiconductor compositions. • Characterization of responsivity and dark current of photodiodes from 12 to 300 K. [ABSTRACT FROM AUTHOR]

This study proposes a new silicon X-ray sensor structure for photon-counting computed tomography (CT), which is a next-generation low-dose X-ray imaging technique. Silicon, which is inexpensive and has excellent processability and a lower reverse bias voltage of several tens of volts, as well as charge transport properties, is used as the sensor material. Using silicon trench photodiodes and horizontal X-ray irradiation method, we can achieve the performance required for photon-counting CT, including a signal response time of less than 100 ns and an exposure dose two orders of magnitude lower than that of conventional CT at a low cost, long device lifetime, and high reliability. The proposed sensor was fabricated, and its photon-counting effectiveness was estimated using 4.2 MeV single $\alpha $ -ray and 60 keV single $\gamma $ -ray photon. The pulse height spectra derived from the $\alpha $ -rays and $\gamma $ -rays were obtained with a low bias voltage of 20 V. For the first time, a single radiation detection pulse was observed, and the pulse height spectra were obtained using silicon trench photodiodes. Furthermore, $\gamma $ -ray count rate, detection efficiency, and pulse rise time proportional to the signal charge collection time were estimated using 60 keV $\gamma $ -rays.

Transparent diodes formed by a heterojunction between p-type CuS–ZnS and n-type ZnO thin films were fabricated by sequential chemical bath deposition and sol-gel spin coating. The diodes are transparent in the visible (≈70% at 550 nm) and exhibit a good rectifying characteristics, with If/Ir ratios of up to 800 at ±1 V, higher than most of the reported solution-processed diodes measured at a similar bias. More importantly, when operated as a self-powered (zero bias) UV photodetector, they show stable and fast (

Transparent diodes formed by a heterojunction between p-type CuS–ZnS and n-type ZnO thin films were fabricated by sequential chemical bath deposition and sol-gel spin coating. The diodes are transparent in the visible (≈70% at 550 nm) and exhibit a good rectifying characteristics, with If/Ir ratios of up to 800 at ±1 V, higher than most of the reported solution-processed diodes measured at a similar bias. More importantly, when operated as a self-powered (zero bias) UV photodetector, they show stable and fast (

Two custom-made In0.5Ga0.5P p+-i-n+ circular mesa spectroscopic X-ray photodiodes with different diameters (200 μm and 400 μm) and a 5 μm i layer have been characterized for their response to X-ray photons within the energy range 4.95 keV to 21.17 keV. The photodiodes, operating uncooled at 30 °C, were coupled, in turn, to the same custom-made charge-sensitive preamplifier. X-ray fluorescence spectra of high-purity calibration foils excited by a Mo target X-ray tube were accumulated. The energy resolution (Full Width at Half Maximum) increased from 0.79 ± 0.02 keV at 4.95 keV to 0.83 ± 0.02 keV at 21.17 keV, and from 1.12 ± 0.02 keV at 4.95 keV to 1.15 ± 0.02 keV at 21.17 keV, when using the 200 μm and 400 μm diameter devices, respectively. Energy resolution broadening with increasing energy was attributed to increasing Fano noise (negligible incomplete charge collection noise was suggested); for the first time, the Fano factor for In0.5Ga0.5P was experimentally determined to be 0.13, suggesting a Fano limited energy resolution of 145 eV at 5.9 keV. The charge output of each system had a linear relationship with photon energy, across the investigated energy range. The count rate of both spectroscopic systems increased linearly with varying X-ray tube current up to ∼105 photons s−1 cm−2 incident photon fluences. The development of In0.5Ga0.5P based spectrometers is particularly important for hard X/γ-ray astronomy, due to the material's large linear X-ray and γ-ray absorption coefficients and the ability to operate uncooled at high temperatures. [ABSTRACT FROM AUTHOR]

Molecular beam epitaxy of Ge (111) thin films on epitaxial-Gd2O3/Si(111) substrates is reported, along with a systematic investigation of the evolution of Ge growth and structural defects in the grown epilayer. While Ge growth begins in the Volmer-Weber growth mode, the resultant islands coalesce within the first ∼10 nm of growth, beyond which a smooth two-dimensional surface evolves. Coalescence of the initially formed islands results in the formation of rotation and reflection microtwins, which constitute a volume fraction of less than 1%. It is also observed that while the stacking sequence of the (111) planes in the Ge epilayer is similar to that of the Si substrate, the (111) planes of the Gd2O3 epilayer are rotated by 180° about the [111] direction. In metal-semiconductor-metal Schottky photodiodes fabricated with these all-epitaxial Ge-on-insulator (GeOI) samples, significant suppression of dark current is observed due to the presence of the Gd2O3 epilayer. These results are promising for applications of these GeOI structures as virtual substrates or for realization of high-speed group-IV photonic components. [ABSTRACT FROM AUTHOR]

Low-cost shortwave infrared detectors have great potential for emerging civilian night-vision applications. This paper reports the characteristics of Ge0.89Sn0.11 photodiodes monolithically grown on a Si substrate that holds great promise for those applications. At room temperature, the 500 μm diameter active area device demonstrated a longwave cutoff of 2.65 μm and a responsivity of 0.32 A/W at 2 μm, which corresponds to an external quantum efficiency of 20% without any contribution from the Ge buffer layer. The measured peak specific detectivity at 300 K and 77 K is 1.7 × 109 Jones and 4.3 × 109 Jones, respectively. The specific detectivity at 77 K is only one-order-of-magnitude lower than that of the market dominating extended-InGaAs photodiode. The detailed device analysis indicated that the 700-nm thick fully relaxed high-quality GeSn absorbing layer and the modified depletion region lead to the above-mentioned device performance. [ABSTRACT FROM AUTHOR]

A lateral-type spin-photodiode having a refracting facet on a side edge of the device is proposed and demonstrated at room temperature. The light shed horizontally on the side of the device is refracted and introduced directly into a thin InGaAs active layer under the spin-detecting Fe contact in which spin-polarized carriers are generated and injected into the Fe contact through a crystalline AlOx tunnel barrier. Experiments have been carried out with a circular polarization spectrometry set up, through which the helicity-dependent photocurrent component, ΔI, is obtained with the conversion efficiency F ≈ 0.4%, where F is the ratio between ΔI and total photocurrent Iph. This value is the highest reported so far for pure lateral-type spin-photodiodes. It is discussed through the analysis with a model consisting of drift-diffusion and quantum tunneling equations that a factor that limits the F value is unoccupied spin-polarized density-of-states of Fe in energy region into which the spin-polarized electrons in a semiconductor are injected. [ABSTRACT FROM AUTHOR]

The large dark current increase near the breakdown voltage of an InGaAs/InP avalanche photodiode is observed and analyzed from the aspect of bulk defects in the device materials. The trap level information is extracted from the temperature-dependent electrical characteristics of the device and the low temperature photoluminescence spectrum of the materials. Simulation results with the extracted trap level taken into consideration show that the trap is in the InP multiplication layer and the trap assisted tunneling current induced by the trap is the main cause of the large dark current increase with the bias from the punch-through voltage to 95% breakdown voltage. [ABSTRACT FROM AUTHOR]

We developed a theoretical approach that employs first-principles Hamiltonians, tight-binding Hamiltonians, and Green's function techniques to obtain energy levels arising from native point defects (NPDs) in InAs-GaSb and InAs-InAs1-xSbx strained layer superlattice (SLS) systems. In InAs and GaSb regions, we considered four types of NPDs—anion vacancy, cation vacancy, anion anti-site, and cation anti-site—as well as isoelectronic substitution at anion sites (Sb at the As site and As at the Sb site). Additionally, we considered three types of defects—the cation at the second anion site, the second anion at the cation site, and second anion vacancy—in the InAs1-xSbx alloy region of the SLS. For a selected few designs, we studied NPDs both in the bulk region and near the interfaces of the SLS. We have considered 12 designs of InAs-GaSb systems and two designs of InAs-InAs0.7Sb0.3 systems lattice-matched to the GaSb substrate. The calculated defect levels not only agreed well with available measurements, but also revealed the connection between mid-gap levels and specific NPDs. We further calculated defect formation energies both in compounds and in all superlattices considered above. Since the absolute value of defect formation energy depends considerably on growth conditions, we evaluated the formation energies in SLS with respect to their value in the corresponding bulk or alloy. The calculated defect formation energies, together with defect energy level results, allow us to identify a few promising SLS designs for high-performing photodetectors. [ABSTRACT FROM AUTHOR]

Photodiodes are fundamental components in modern optoelectronics. Heterojunction photodiodes, simply configured by two different contact materials, have been a hot research topic for many years. Currently reported self‐biased heterojunction photodiodes routinely have external quantum efficiency (EQE) significantly below 100% due to optical and electrical losses. Herein, an approach that virtually overcomes this 100% EQE challenge via low‐aspect‐ratio nanostructures and drift‐dominated photocarrier transport in a heterojunction photodiode is proposed. Broadband near‐ideal EQE is achieved in nanocrystal indium tin oxide/black silicon (nc‐ITO/b‐Si) Schottky photodiodes. The b‐Si comprises nanostalagmites which balance the antireflection effect and surface morphology. The built‐in electric field is explored to match the optical generation profile, realizing enhanced photocarrier transport over a broadband of photogeneration. The devices exhibit unprecedented EQE among the reported leading‐edge heterojunction photodiodes: average EQE surpasses ≈98% for wavelengths of 570–925 nm, while overall EQE is greater than ≈95% from 500 to 960 nm. Further, only elementary fabrication techniques are explored to achieve these excellent device properties. A heart rate sensor driven by nanowatt faint light is demonstrated, indicating the enormous potential of this near‐ideal b‐Si photodiode for low power consuming applications. [ABSTRACT FROM AUTHOR]

We present a readout scheme for CMOS image sensors that can be used to achieve arbitrarily high dynamic range (HDR) in principle. The linear full well capacity (LFWC) in high signal regions was extended 50 times from 20 to 984 ke $^{-}$ via an interlaced row-wise readout order, while the noise floor remained unchanged in low signal regions, resulting in a 34-dB increase in DR. The peak signal-to-noise ratio (PSNR) is increased in a continuous fashion from 43 to 60 dB. This was achieved by summing user-selected rows that were read out multiple times. Centroiding uncertainties were lowered when template-fitting a projected pattern, compared to the standard readout scheme. Example applications are aimed at scientific imaging due to the linearity and PSNR increase. [ABSTRACT FROM AUTHOR]

In this article, a new Schottky diode based on a transparent conducting polymer 2-(4-fluorophenyl)-2-oxoethyl-2-methylprop-2-enoate (PFPAMA) that is doped up to 5% with ZnO is presented. PFPAMA is a promising transparent polymer that is inclined towards n-type behavior with the potential to be used as an electron transport layer. Each device had the Al/p-Si:(PFPAMA:ZnO)/Al structure. The diode ideality factor was found to depend on bias and illumination but the calculated interface state density is lower by 3 orders of magnitude than for most reported Al/p-Si diodes, suggesting that the presence of the polymer suppresses interface states. The measured electrical and photoresponse characteristics confirm that the resulting diodes are suitable for fast photodiodes over the intensity range of dark to 100 mW/cm2 whose performance can be optimized by ZnO doping. The application of functionalized polymers on p-silicon for sensing applications is an emerging field. [ABSTRACT FROM AUTHOR]

Multifunctional organic optoelectronic devices are of great significance for the development of low‐energy consumption and space‐constrained systems. Herein, multifunctional organic photodiodes integrating transient light detection and photo‐synaptic functions in one device are unprecedentedly achieved upon readily changing the direction of the external bias. Under negative bias, the devices exhibit excellent photodetection performance with high shot‐noise‐limited specific detectivity (Dsh∗\[D_{sh}^*\] > 1013 Jones) in the range from ultraviolet, visible, to near infrared and large linear dynamic range (188 dB at 915 nm), which are among the best organic photodetectors. Interestingly, the photodiode devices change to work as organic photosynapses upon tuning the external bias to be positive. Associative learning behavior is successfully simulated in an all‐optical way, while high image recognition accuracy (>80%) is realized based on artificial neural network. The mechanism studies reveal that the interface energy barrier is critical for achieving the multi‐function in one device. Finally, the universality of electrically switchable transient light detection and photo‐synaptic functions is further studied. This work provides a novel method for constructing vertical diode‐type organic optical synapses and developing multifunctional organic electronics. [ABSTRACT FROM AUTHOR]

In this article, we show that desktop speakers' internal (electrical circuitry) and external (reflective diaphragm) design may expose users to confidential information leakage. We demonstrate that these flaws are present in billions of devices produced by global manufacturers and discuss countermeasures. [ABSTRACT FROM AUTHOR]

Cd and Co metal centered nicotinamide/nicotinic acid complexes were synthesized by chemical reactions. The complexes were characterized by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT‐IR), powder X‐ray diffractometer (P‐XRD), ultraviolet–visible (UV–Vis) spectrometer, and scanning electron microscopy (SEM) with energy dispersive X‐ray (EDX) detector. The complexes were used as interfacial layers in between Al and p‐Si to fabricate Al/Cd‐complex/p‐Si and Al/Co‐complex/p‐Si metal semiconductor devices. The devices were characterized by current–voltage (I‐V) and current‐time (I‐t) measurements under dark and various light power intensities. The ideality factor, barrier height, and series resistance values were extracted from I‐V measurements and discussed in detail by various techniques. The I‐t measurements were used to derive various detector parameters such as responsivity, photosensitivity, and specific detectivity for various power values and wavelength regions. The devices exhibited good photodiode and photodetector performance according to results, and they can be improved for optoelectronic applications. [ABSTRACT FROM AUTHOR]

Comprehensive analysis of small-signal equivalent circuit models for GaAs-based PIN diodes is performed in this article. The analysis provides the equivalent circuit models for PIN diode operation in four different operation modes. A compact nonlinear equivalent circuit model has been developed which takes into account the dc/ac frequency dispersion of the diode dynamic resistance. In order to verify the validity of the proposed circuit model, the comparison between the modeled and measurement data is given, good fitting is obtained for GaAs-based PIN diode. [ABSTRACT FROM AUTHOR]

In this article, a unique structure of InP/InGaAs uni-traveling-carrier photodiode (UTC-PD) is proposed. Compared with the one-sided junction photodiode, the UTC-PD has the advantages of a simpler epitaxial layer structure while maintaining the characteristics of high bandwidth and high output power loss profile. Simulated results show that a large built-in electric field can be generated under illumination, which aids UTC carrier velocity. The merits of the new structure are compared to a standard UTC-PD photodiode in terms of improved electric field and carrier concentration response. It is demonstrated that the photogeneration and light absorption of UTC-PDs are improved by incorporating a step-like internal texture of cones and dots profile in the photo absorption layer. The simulated device shows a peak electrical 3-dB bandwidth of 65 GHz at a low light intensity and reverse bias voltage. The performance characteristics of 1-D and 2-D UTC-PD simulations, including internal electric field distribution, energy band diagram, carrier concentration, and power loss distribution, are carefully studied. A theoretical discussion of the working principle and key performance characteristics of a UTC-PD enhanced by heterojunction design is reported. The entire physical environment is modeled and simulated through the finite element method (FEM) using commercial software. The proposed photodiode structure configuration is designed and optimized for photodetectors for high RF frequencies at different light intensities. To the best of our knowledge, the obtained bandwidth and electric field response is the fastest among those reported for other various higher wavelength photodiodes. [ABSTRACT FROM AUTHOR]

High-speed, high-photoresponse, low-dark current photodetectors with monolithic integration compatibility on a single silicon chip have a vital role in fast optical communication. Schottky barrier junctions provide ultrahigh frequency bandwidth, which makes them suitable for a high-speed data rate optical transition system. In this article, we proposed the novel design of a fast silicon Schottky photodiode (SPD) with reduced dark current and enhanced photocurrent to produce an acceptable photo-to-dark current ratio. A differential Schottky diode is used in series with the designed SPD to reduce the final dark current delivered to the next signal conditioner electronics. A periodic plasmonic array is applied on the metallic Schottky contact layer to localize the illuminated light in the depletion region of Schottky contact and increase light absorption, which results in enhanced photocurrent. The simulation of the device shows a photo-to-dark current ratio of ${2.7} \times {10}^{{4}}$ at room temperature and 1-V biasing voltage, which is much greater than the reported data. Moreover, the design results in a complementary metal–oxide–semiconductor (CMOS)-compatible photodiode (PD) with 28-time reduced dark current and 3.3-time photocurrent enhancement with an ultrafast impulse response of 3 ps and a response time of about 18 ps that are attractive for ultra-fast data communication applications in 850-nm region. [ABSTRACT FROM AUTHOR]

PM6:Y6 is adopted as the active layer to prepare highly efficient organic photodetectors (OPDs), which is applied to realize a biometric sensor for real‐time heart‐rate monitoring. Here, the effects of the device structure, thickness, deposition process, and solvent on the subsequent performance of the OPDs are examined. Through judicious choice of the fabrication conditions, an OPD is obtained displaying a dark current density of less than 8.77 × 10−10 A cm−2, a responsivity of greater than 0.516 A W−1, and a high detectivity of 3.1 × 1013 Jones, measured at bias of −2 V (870 nm). This OPD featured a wide linear dynamic range (LDR, 530 nm) of 104 dB at −2 V, an ultrahigh cutoff frequency (750 kHz) and rise/fall times of less than 220 ns under a reverse bias of −2 V. This sub‐microsecond response and high detectivity is comparable with, and in some cases better than, those of the state‐of‐the‐art perovskite‐PDs and Si‐PDs. The OPD displays consistent responses, good repeatability, and stability [ambient: 50% humidity, 25 °C)]. The air‐stable and portable OPD‐based photoplethysmogram system provides clear signal resolution, potentially benefitting its applicability to blood pressure monitoring. [ABSTRACT FROM AUTHOR]

This paper has been designed to study whether photodiodes and supervised machine learning (ML) algorithms are sufficient to automatically classify weld defects caused by simultaneous variation of the part-to-part gap and laser power during remote laser welding (RLW) of thin foils, with applications in battery tabs. Photodiodes are used as the primary source of data and are collected in real-time during RLW of copper-to-steel thin foils in the lap joint. Experiments are carried out by the nLight Compact 3 kW fiber laser integrated with the Scout-200 2D scanner. The paper reviews and compares seven supervised ML algorithms (namely, k-nearest neighbors, decision tree, random forest, Naïve–Bayes, support vector machine, discriminant analysis, and discrete wavelet transform combined with the neural network) for automatic classification of weld defects. Up to 97% classification rate is obtained for scenarios with simultaneous variations of weld penetration depth and part-to-part gap. The main causes of misclassification are imputed to the interaction between welding parameters (part-to-part gap and laser power) and process instability at high part-to-part gap (high variation in the process not captured by the photodiodes). Arising opportunities for further development based on sensor fusion, integration with real-time multiphysical simulation, and semi-supervised ML are discussed throughout the paper. [ABSTRACT FROM AUTHOR]

The explosive demand for a wide range of data processing has sparked interest towards a new logic gate platform as the existing electronic logic gates face limitations in accurate and fast computing. Accordingly, optoelectronic logic gates (OELGs) using photodiodes are of significant interest due to their broad bandwidth and fast data transmission, but complex configuration, power consumption, and low reliability issues are still inherent in these systems. Herein, we present a novel all-in-one OELG based on the bipolar spectral photoresponse characteristics of a self-powered perovskite photodetector (SPPD) having a back-to-back p+-i-n-p-p+ diode structure. Five representative logic gates ("AND", "OR", "NAND", "NOR", and "NOT") are demonstrated with only a single SPPD via the photocurrent polarity control. For practical applications, we propose a universal OELG platform of integrated 8 × 8 SPPD pixels, demonstrating the 100% accuracy in five logic gate operations irrelevant to current variation between pixels. The authors present a novel all-in-one optoelectronic logic gates based on the bipolar spectral photo-response characteristics of self-powered perovskite photodetector. Five representative logic gates are demonstrated with only a single detector via photocurrent polarity control. [ABSTRACT FROM AUTHOR]

Silicon photonics is promising for artificial neural networks computing owing to its superior interconnect bandwidth, low energy consumption and scalable fabrication. However, the lack of silicon-integrated and monitorable optical neurons limits its revolution in large-scale artificial neural networks. Here, we highlight nonlinear germanium-silicon photodiodes to construct on-chip optical neurons and a self-monitored all-optical neural network. With specifically engineered optical-to-optical and optical-to-electrical responses, the proposed neuron merges the all-optical activation and non-intrusive monitoring functions in a compact footprint of 4.3 × 8 μm2. Experimentally, a scalable three-layer photonic neural network enables in situ training and learning in object classification and semantic segmentation tasks. The performance of this neuron implemented in a deep-scale neural network is further confirmed via handwriting recognition, achieving a high accuracy of 97.3%. We believe this work will enable future large-scale photonic intelligent processors with more functionalities but simplified architecture. Large-scale silicon-based integrated artificial neural networks lack of silicon-integrated optical neurons. Here, Yu et al, report a self-monitored all-optical neural network enabled by nonlinear germanium-silicon photodiodes, making the photonic neural network more versatile and compact. [ABSTRACT FROM AUTHOR]

Co‐integration of visible and infrared (IR) photodetection into a simple configuration is of essential importance for broadband multispectral imaging, and various heterostructures based on group IV, III–V, and recent 2D semiconductors have been studied in efforts to circumvent limits on photoresponsivity and response speed in IR ranges. In this work, a vertically stacked double heterojunction (DHJ) photodiode (PD) with ultrawide‐bandgap gallium oxide (Ga2O3) is reported on, and the performance is compared with p‐WSe2/n‐Ge PD. The fabricated n‐Ga2O3/p‐WSe2/n‐Ge PD responds to a broad spectral range from vis to shortwave IR (SWIR) (1550 nm) with a response time of ≈2.6 µs and responsivity of 17.2 A W−1. The superior performance is attributed to amplified photocurrent gains, and the additional n‐Ga2O3 has a high electron carrier density with negligible hole density at room temperature and thus, can play a role as an electron reservoir while being transparent to the spectral ranges. vScanning photocurrent microscopy analysis is performed to provide the mechanism. The demonstrated SWIR imaging shows that the proposed DHJ provides a potential pathway for high‐speed multispectral vision applications. [ABSTRACT FROM AUTHOR]

The state of the art method for fingerprinting digital cameras focuses on the non-uniform output of an array of photodiodes due to the distinct construction of the PN junction when excited by photons. This photo-response non-uniformity (PRNU) noise has shown to be effective but ignores knowledge of image sensor output under equilibrium states without excitation (dark current). The dark current response (DSN) traditionally has been deemed unsuitable as a source of fingerprinting as it is unstable across multiple variables including exposure time and temperature. As such it is currently ignored even though studies have shown it to be a viable method similar to that of PRNU. We hypothesize that DSN is not only a viable method for forensic identification but, through proper analysis of the thermal component, can lead to insights regarding the specific temperature at which an individual image under test was taken. We also show that digital filtering based on the discrete cosine transformation, rather than the state-of-the-art wavelet filtering, there is significant computational gain albeit with some performance degradation. This approach is beneficial for triage purposes. [ABSTRACT FROM AUTHOR]

Solid‐state devices capable of controlling light‐responsive charge transport at the molecular scale are essential for developing molecular optoelectronic technology. Here, a solid‐state molecular photodiode device constructed by forming van der Waals (vdW) heterojunctions between standard molecular self‐assembled monolayers and two‐dimensional semiconductors such as WSe2 is reported. In particular, two non‐functionalized molecular species used herein (i.e., tridecafluoro‐1‐octanethiol and 1‐octanethiol) enable bidirectional modulation of the interface band alignment with WSe2, depending on their dipole orientations. This dipole‐induced band modulation at the vdW heterointerface leads to the opposite change of both photoswitching polarity and rectifying characteristics. Furthermore, compared with other molecular or 2D photodiodes at a similar scale, these heterojunction devices exhibit significantly enhanced photo‐responsive performances in terms of photocurrent magnitude, open‐circuit potential, and switching speed. This study proposes a novel concept of the solid‐state molecular optoelectronic device with controlled functions and enhanced performances. [ABSTRACT FROM AUTHOR]

Organic-inorganic halide perovskites have demonstrated preeminent optoelectronic performance in recent years due to their unique material properties, and have shown great potential in the field of photodetectors. In this study, a coupled opto-electronic model is constructed to reveal the hidden mechanism of enhancing the performance of perovskite photodetectors that are suitable for both inverted and regular structure doped p-i-n perovskite photodiodes. Upon illumination, the generation rate of photogenerated carriers is calculated followed by carrier density distribution, which serves as a coupled joint to further analyze the recombination rate, electric field strength, and current density of carriers under different doping types and densities. Moreover, experiments were carried out in which the doping types and densities of the active layer were regulated by changing the precursor ratios. With optimal doping conditions, the inverted and regular perovskite photodiodes achieved an external quantum efficiency of 74.83% and 73.36%, and a responsivity of 0.417 and 0.404 A/W, respectively. The constructed coupled opto-electronic model reveals the hidden mechanism and along with the doping strategy, this study provides important guidance for further analysis and improvement of perovskite-based photodiodes. [ABSTRACT FROM AUTHOR]

This article analyses the effect of noise and nonlinearity in optoelectronic phase-locked loops (OEPLLs). The OEPLL phase-locks a microwave oscillator on the envelope of the optical pulse train from a mode-locked laser (MLL). The phase detector of this type of OEPLL is called a balanced optical microwave phase detector (BOMPD) and operates in a mixed electro-optical domain. The main noise sources in a BOMPD, such as shot noise of photodiodes, generation-recombination noise of photodiodes, relative intensity noise of the laser, and noise of the bias voltage applied to the BOMPD. are discussed. The nonlinear behavior of the BOMPD with respect to the intensity of the optical field and the amplitude of the RF voltage is discussed. An OEPLL that can lock on the harmonics and interharmonics of the MLL repetition rate is demonstrated. The OEPLL has an in-band phase noise of below −150 dBc/Hz at 100-kHz offset frequency for a carrier frequency of 10 GHz. This phase noise level is 10–20 dB better than state-of-the-art commercial frequency synthesizers. [ABSTRACT FROM AUTHOR]

Comparative characterization of phosphorus diffusion from planar sources and liquid-phase diffusion by using PCl3 in technology for manufacturing silicon p-i-n photodiodes was carried out. The quantitative analysis of dislocations formed when using different variants and modes of diffusion has been performed. The influence of dislocation number on the dark current density and responsivity of photodetectors has been studied. A table has been given for estimation of surface resistance with account of colour inherent to phosphorosilicate glass after doping phosphorus into the surface layer. [ABSTRACT FROM AUTHOR]

Recently, the main issue for developing the latest small pixels is maintaining the full-well capacity (FWC) while minimizing image lag as the pixel pitch is scaled down within the sub-micron scale. In this letter, the FWC and image lag characteristics are optimized by varying the photodiode (PD) doping profiles in $0.5~\mu \text{m}$ CMOS image sensors with vertical transfer gates (VTGs) for the first time. Measurements and simulated results of various pitch generations are correlated to propose the most desirable PD doping conditions for $0.5~\mu \text{m}$ pixels which have not been developed yet. As a result, the ceiling position of the top PD doping significantly affects the image lag characteristics resulting in the lowest image lag when increasing the ceiling by 30% from the initial position. In conclusion, a fruitful guideline for photodiode design in 3D active pixel sensors is provided for optimization of FWC and image lag in $0.5~\mu \text{m}$ pixel pitches. Also, this methodology associating potential curve analysis can be of potential use for development in ultra-small pixel pitches in the near future. [ABSTRACT FROM AUTHOR]

For radiation hardened image sensors, a Silicon-On-Insulator (SOI) -Si/ 4H-SiC hybrid pixel device was developed. The hybrid pixel device consists of one Si photodiode and three 4H-SiC nMOSFETs. At fabrication, SOI substrate was directly bonded on 4H-SiC substrate via SiO2. After bonding, the base silicon substrate and Buried Oxide (BOX) were removed by TMAH wet-etching. By using this SOI-Si/ 4H-SiC substrate, the SOI-Si photodiodes and 4H-SiC nMOSFETs were integrated in the same substrate. As a result, a response of the SOI-Si/ 4H-SiC hybrid pixel device to light illumination was successfully demonstrated. [ABSTRACT FROM AUTHOR]

By combining information such as genomics, proteomics, and metabolomics data, multiomics methodologies have the potential to reveal the otherwise invisible processes of carcinogenesis. Using these data, a new-generation point-of-care (POC) device may support patient care through rapid diagnosis involving accurate and simultaneous multiomics measurements. In this work, we present a proof-of-concept portable system capable of measuring a metabolite (glutamate) and a protein [proteolytically active prostate-specific antigen (aPSA)] simultaneously on a single device in a 2-min interval using on-chip optical methods. The device has the potential to improve the current diagnostic pathways of prostate cancer (PCa) by reducing the high false-positive rate with the widely used total prostate-specific antigen (tPSA) test. We demonstrate a simultaneous assay of glutamate and aPSA in buffer and synthetic urine. For the glutamate assay, the limit of detection (LOD) and resolution were found to be 0.9 and $2.7 {\boldsymbol {\mu }}\text{M}$ , respectively. The LOD and resolution for aPSA were 0.5 and 2.0 ng $/$ ml, respectively. The LOD and resolution achieved using this device are, therefore, in line with human physiological ranges. The platform is suitable for accommodating two independent optical assays, and, therefore, chemistry can be modified to measure different analytes regardless of their nature. This technological breakthrough has the potential to deliver an accurate multiomics portable device for PCa and may be extended to other diseases. [ABSTRACT FROM AUTHOR]

In this study, ZnO nanorods (ZnO-NR) were prepared on n-Si wafer by hydrothermal method. Structural and morphologic properties of ZnO nanostructures were investigated through XRD and SEM method. The illumination impacts on the current-voltage (I-V) measurements of the prepared Al/ZnO-NR/n-Si diode were explored in the dark and different illumination intensities (20-100 mW/cm²) between ± 1.5 V bias voltage range. The Schottky diode barrier height value had an increasing trend with increasing illumination intensity from 20 to 100 mW/cm² while the ideality factor had a decreasing trend with the increase of photocurrent. The temporary photocurrent increases as illumination intensity increases. The slope (α) of the logIph-logP curve was obtained as 0.618 and this slope confirmed that this ZnO nanorod shows photoconducting behavior. The short-circuit current (Isc) and open-circuit voltage (Voc) values were obtained to be 774.08 µA and 0.24 V under 100 mW/cm² illumination intensity, respectively. The prepared Al/ZnO-NR/n-Si diode showed both photodiode and photovoltaic properties under different light intensities. It was concluded that the prepared Al/ZnO-NR/n-Si diode can be used in the optoelectronic applications, especially for the photodiode industry. [ABSTRACT FROM AUTHOR]

The paper presents a design and performance analysis of a photosensor device enabling the measurement of the visible light illuminance. The sensor is designed for use in the light metering matrix of a mobile measurement platform allowing the correct operation of inpavement airport lamps. This kind of control can be required by regulations and must meet the standards defined by the European Union Aviation Safety Agency (EASA). An important assumption of the solution was to obtain the highest possible speed of a measurement acquisition so that the control process would take place in a relatively short time. The proposed module concept is dedicated to the task of testing the quality of airport lamps, due to the characteristics of the photosensitive elements matching the light beams emitted by luminaries. The device is based on a VTP1220FBH photodiode and an ATmega328P microcontroller, which, in addition to the analogue-to-digital conversion and correction, sends the results back to the master unit via the I2C bus. [ABSTRACT FROM AUTHOR]

In this study, the symmetrical copper-phthalocyanine (CuPc) was coated on p-Si wafer by spin-coating method. The photoresponse and electrical properties of the Al/symmetrical CuPc/p-Si structures/diodes were investigated at room temperature using by current–voltage/time (I–V/t) and capacitance/conductance-voltage/frequency (C/G-V/f) measurements under dark and various solar irradiances (between 10 and 100 mW/cm2). The main electronic parameters of the diode, which included ideality factor (n), barrier height (Φb), rectification ratio (RR = IF/IR), series resistance (Rs), and interface states density (Nss) were computed. The experimental results reveal that the photocurrent level of the diodes is controlled by various solar irradiances. The m exponent of the double-logarithmic Iph–P plot was found to be 1.12, confirming linear photoconduction behavior. The Al/symmetrical CuPc/p-Si structure can be used as a photo device/sensor in electro-optic and photonics. [ABSTRACT FROM AUTHOR]

The concept of dual-polarized reconfigurable reflectarray (RRA) featuring dual-polarized beam control is proposed and demonstrated using a dual-channel programmable metasurface. The p-i-n diodes are incorporated into each metasurface element as the active components to provide independent phase control in two orthogonal polarization channels. By altering the working states of each p-i-n diode, well-defined beam scanning can be obtained. Element design, focal diameter ratio selection, and discretized phase distributions are carefully optimized to ensure stable radiation performance of the proposed RRA. As verification, a prototype consisting of 20 $\times20$ elements is fabricated and measured, which is controlled by a field programmable gate array-based controller. Measured results show that wide-angle beam scanning up to ±40° can be obtained around 7.45 GHz, with peak gains of 21.13 and 20.89 dBi in dual channels, corresponding to aperture efficiencies of 16.35% and 15.47%. The proposed dual-polarized RRA brings a new freedom in polarization manipulations for versatile beam scanning, which provides promising applications in wireless communication and tracking/detecting systems. [ABSTRACT FROM AUTHOR]

Lead-based organic–inorganic hybrid perovskite single crystals (OIHP SCs) offer promising opportunity for X-ray detection and imaging owing to their high X-ray attenuation coefficient, excellent optoelectronic properties, and simple fabrication processes. Nevertheless, it remains a key challenge to reduce its dark current and meanwhile maintain a high sensitivity. Herein, we developed an on-substrate method for growing methylamine lead bromide (MAPbBr3) SCs on aluminum oxide (Al2O3) layer coated indium tin oxide (ITO) glass. The photodiode based on this approach exhibits an ultralow-dark-current density of 1 nA cm−2 at an operative voltage of −5 V, a signal-to-noise ratio (SNR) more than 80 dB, and meanwhile retaining a high X-ray sensitivity of 2.02 $\times 10^{{3}}\,\, \mu \text{C}\cdot $ ${\mathrm {Gy}}_{\text {air}}^{-1} \cdot $ cm−2. Our further investigation reveals that the dark current was reduced due to two beneficial effects of the Al2O3 layer in tandem, including the interfacial defect passivation and blocking of hole injection by increased interfacial energy barrier. Our approach sheds light on advancing the fabrication of high-performance OIHP SCs-based X-ray sensors that can be potentially integrated with large-area readout panel at low temperature. [ABSTRACT FROM AUTHOR]

Photodetection based on assemblies of quantum dots (QDs) is able to tie the advantages of both the conventional photodetector and unique electronic properties of zero-dimensional structures in an unprecedented way. However, the biggest drawback of QDs is the small absorbance of infrared radiation due to the low density of the states coupled to the dots. In this paper, we report on the Ge/Si QD pin photodiodes integrated with photon-trapping hole array structures of various thicknesses. The aim of this study was to search for the hole array thickness that provided the maximum optical response of the light-trapping Ge/Si QD detectors. With this purpose, the embedded hole arrays were etched to different depths ranging from 100 to 550 nm. By micropatterning Ge/Si QD photodiodes, we were able to redirect normal incident light laterally along the plane of the dots, therefore facilitating the optical conversion of the near-infrared photodetectors due to elongation of the effective absorption length. Compared with the conventional flat photodetector, the responsivity of all microstructured devices had a polarization-independent improvement in the 1.0–1.8-μm wavelength range. The maximum photocurrent enhancement factor (≈50× at 1.7 μm) was achieved when the thickness of the photon-trapping structure reached the depth of the buried QD layers. [ABSTRACT FROM AUTHOR]

We investigated the effects of the crystalline state for seed layers (SLs) on the growth morphology and material characteristics for hydrothermally grown ZnO nanorods (NRs). For this, preheating (PH) at different temperatures (100–300 °C) and O2 plasma treatment (PT) for 9 min were performed during the growth of SLs on p-Si by the aqueous solution-based method to provide the characteristic change on the NR growth platform. An improvement in material properties was achieved from the ZnO NRs grown on the SL crystals of enhanced crystalline quality in terms of the increased preferred orientation (002), the higher UV emission with suppressed deep-level emissions, the recovery of O/Zn stoichiometry, and the reduction of various intrinsic defects. Ultraviolet photodiodes of a p-Si/n-ZnO-NR structure fabricated under the SL conditions of O2 PT and PH at 100 °C showed a significantly enhanced on-off current ratio of ~90 at +5 V and faster photoresponse characteristics presenting a reduction in the fall time from 16 to 9 s. [ABSTRACT FROM AUTHOR]

HERD is a future experiment for the direct detection of high energy cosmic rays. The instrument is based on a calorimeter optimized not only for a good energy resolution but also for a large acceptance. Each crystal composing the calorimeter is equipped with two read-out systems: one based on wavelength-shifting fibers and the other based on two photodiodes with different active areas assembled in a monolithic package. In this paper, we describe the photodiode read-out system, focusing on experimental requirements, design and estimated performances. Finally, we show how these features lead to the flight model project of the photodiode read-out system. [ABSTRACT FROM AUTHOR]

High-quality $\beta $ -Ga2O3 films were prepared via the metal organic chemical vapor deposition method and construction of metal–semiconductor–metal–structured photodetectors (PDs) with varying parameters, including length, width, and distance of the Ti/Au interdigital electrodes. Under a 10 V bias and UV light illumination ($50~\mu $ W/cm2), the peak response of PDs is present in the solar-blind region (254 nm), and the responsivity is as high as $1.87\times10$ 5 A/W. The cut-off wavelength is ~266 nm, with a deep UV/visible light responsivity rejection ratio (R254 nm/R400 nm) of ~102. The light–dark current ratio reaches 105, the detectivity is about $3.37\times10$ 14 Jones, and the rise and decay response time is < 1 s. These high performances are attributed to defect center trapping carriers, yielding inconsistent electron and hole collection efficiency. Additionally, the nonlinear effect between light intensity and photocurrent that is induced by avalanche ionization under a high electric field (50 V) is demonstrated. This study might be of great value for the design and fabrication of high-performance solar-blind UV PDs. [ABSTRACT FROM AUTHOR]

Two GaAs p+-i-n+ mesa X-ray photodiodes were characterized for their electrical and photon counting X-ray spectroscopic performance over the temperature range of 100 °C to -20°C. The devices had 10 μm thick i layers with different diameters: 200 μm (D1) and 400 μm (D2). The electrical characterization included dark current and capacitance measurements at internal electric field strengths of up to 50 kV/cm. The determined properties of the two devices were compared with previously reported results that were made with a view to informing the future development of photon counting X-ray spectrometers for harsh environments, e.g., X-ray fluorescence spectroscopy of planetary surfaces in high temperature environments. The best energy resolution obtained (Full Width at Half Maximum at 5.9 keV) decreased from 2.00 keV at 100 °C to 0.66 keV at -20 °C for the spectrometer with D1, and from 2.71 keV at 100 °C to 0.71keV at -20°C for the spectrometer with D2. Dielectric noise was found to be the dominant source of noise in the spectra, apart from at high temperatures and long shaping times, where the main source of photopeak broadening was found to be the white parallel noise. [ABSTRACT FROM AUTHOR]

In this research, the impact of the different zinc (Zn) concentrations on the physical and optoelectronic properties of Bi 2 S 3 nanorods as self-powered and photodiode applications was investigated. The performance of P-N junction photodiodes has been for decades since they are crucial in energy applications. The structure, degree of crystallinity, and shape of Zn-doped Bi 2 S 3 nanorods of various doping percentages formed onto the indium tin oxide (ITO) substrates by the dip coating technique are investigated using X-ray powder diffraction (XRD) and SEM. With increasing illumination time, the current-voltage (I-V) graphs demonstrate a rise in photocurrent. The diode's idealist factor was estimated using the I-V technique under 30 min of light illumination., (© 2024 John Wiley & Sons Ltd.)