Low Dark Noise Research Articles

Parametric Research on the Deep-Junction Silicon SPADs for Wide Spectral Response and Low Dark Count Noise

Parametric Research on the Deep-Junction Silicon SPADs for Wide Spectral Response and Low Dark Count Noise

Optoelectronics of Lead‐Free Antimony‐ and Bismuth‐Based Metal Halides for Sensitive and Low‐Noise Photodetection

AbstractOrganic–inorganic hybrid halide perovskites have emerged as the most promising optoelectronic materials for next‐generation solution‐processed devices, primarily attributed to their distinctive properties such as cost‐effectiveness, facile fabrication process, high light absorption coefficient, tunable bandgap, and relatively high charge carrier mobility. Nevertheless, the presence of Pb elements is inevitable in most high‐performance perovskite optoelectronic devices, posing environmental pollution concerns and impeding their commercialization. In this study, two novel non‐toxic bismuth‐ and antimony‐based perovskite materials with environmentally conscious approaches are developed. Their structures and optoelectronic properties have been systematically characterized. Subsequently, photoconductive‐ and photodiode‐type photodetectors are designed and fabricated. Notably, the photodiode configuration exhibits exceptionally low dark current and noise, superior detection sensitivity, fast response speed, and good device stability. Owing to these superior performance metrics, the devices demonstrate great potential for real applications. Furthermore, this study furnishes a theoretical framework and design perspectives for the solution‐processed semiconductor materials.

A 64 × 128 3D-Stacked SPAD Image Sensor for Low-Light Imaging.

Low-light imaging capabilities are in urgent demand in many fields, such as security surveillance, night-time autonomous driving, wilderness rescue, and environmental monitoring. The excellent performance of SPAD devices gives them significant potential for applications in low-light imaging. This article presents a 64 (rows) × 128 (columns) SPAD image sensor designed for low-light imaging. The chip utilizes a three-dimensional stacking architecture and microlens technology, combined with compact gated pixel circuits designed with thick-gate MOS transistors, which further enhance the SPAD's photosensitivity. The configurable digital control circuit allows for the adjustment of exposure time, enabling the sensor to adapt to different lighting conditions. The chip exhibits very low dark noise levels, with an average DCR of 41.5 cps at 2.4 V excess bias voltage. Additionally, it employs a denoising algorithm specifically developed for the SPAD image sensor, achieving two-dimensional grayscale imaging under 6 × 10-4 lux illumination conditions, demonstrating excellent low-light imaging capabilities. The chip designed in this paper fully leverages the performance advantages of SPAD image sensors and holds promise for applications in various fields requiring low-light imaging capabilities.

High-performance InGaAs/GaAsSb extended short-wave infrared Electron-Injection photodetector

In this paper, we report a high-sensitive extended short-wave infrared (e-SWIR) Electron-Injection (EI) photodetector based on InGaAs/GaAsSb type-II superlattice (T2SL). To achieve high gain and low dark current noise, the EI photodetector involved in this letter employs a multi-layer heterogeneous band structure, composed of InAlAs, GaAsSb and InGaAs/GaAsSb T2SL, which can facilitate electron injection and effectively reduce recombination and thermal generation within the device. Thanks to the unique band alignment, this EI photodetector operates in high-gain linear-mode and requires only a small bias voltage about 0.8 V. At 200 K, the detector exhibits a 100 % cut-off wavelength of ∼ 2.7 μm, a peak responsivity of 3693.2 A/W corresponding to a gain of 7979.0 at 1.4 V, and a gain-normalized dark current density (GNDCD) of 1.4 × 10-6 A/cm2, which results in a remarkable specific detectivity of 6.0 × 1013 cm·Hz1/2/W. When operating at room temperature, this EI photodetector presents a decent responsivity of over 2000.0 A/W. Our results pave a potential way for ultra-sensitive e-SWIR infrared detection at high temperature.

Simulation of a Pulsed Metastable Helium Lidar

Measurements of atmosphere density in the upper thermosphere and exosphere are of great significance for studying space–atmosphere interactions. However, the region from 200 km to 1000 km has been a blind area for traditional ground-based active remote sensing techniques due to the limitation of facilities and the paucity of neutral atmosphere. To fulfill this gap, the University of Science and Technology of China is developing a powerful metastable helium resonance fluorescent lidar incorporating a 2 m aperture telescope, a high-energy 1083 nm pulsed laser, as well as a superconducting nanowire single-photon detector (SNSPD) with high quantum efficiency and low dark noise. The system is described in detail in this work. To evaluate the performance of the lidar system, numerical simulation is implemented. The results show that metastable helium density measurements can be achieved with a relative error of less than 20% above 370 km in winter and less than 200% in 270–460 km in summer, demonstrating the feasibility of metastable helium lidar.

Self‐Assembly PbS Quantum Dot‐Conjugated Polymer Hybrid‐Layered Phototransistor Enables SWIR Photodetection with High Detectivity

AbstractLead sulfide colloid quantum dots (PbS QDs) offer great opportunities to revolutionize large‐area short‐wave infrared (SWIR) detection technologies due to high absorption coefficients and spectral selectivity. However, a critical issue for QDs‐based SWIR detectors is high dark current noise due to thermal carriers and the large amounts of surface defect states induced by the ligand exchange process, which hinders the improvement of the room temperature detectivity and linear dynamic range. Herein, it is demonstrated that these dilemmas can be overcome by adopting a novel hybrid‐layered phototransistor device architecture composed of a self‐assembly high‐mobility organic conduction channel and a bulk heterojunction infrared absorber containing PbS QDs as sensitizers. Strong photo absorption in the photoactive layer creates photogenerated charges that are transferred to the conduction channel, where they recirculate many times due to the long trapped‐electron lifetime in the photoactive layer and the high carrier mobility of the channel. Therefore, low dark current noise and high photoconductive gain are achieved by both electrical gating and photodoping for carrier‐density modulation of phototransistors. Finally, an optimized SWIR phototransistor device with a low room‐temperature dark current of 7 pA and a high detectivity of 8 × 1012 Jones under 1650 nm light illumination is demonstrated.

Large Area Picosecond Photodetector for the Upgrade II of the LHCb RICH

The Large Area Picosecond Photodetector (LAPPD) is a new generation microchannel plate (MCP) photodetector that is currently capturing the attention of detector physicists thanks to its excellent timing resolution, high gain and low dark count rate. It consists of a photocathode that responds to a single photon by producing a photoelectron that enters a pair of microchannel plates, where it is multiplied to a million electrons in a fast-rising pulse that is easily detected. The speed of this process provides the time resolution essential for high intensity environments such as the high luminosity Large Hadron Collider (LHC) at the CERN laboratory. The LAPPD has a large sensitive area, 200 × 200 mm 2, which reduces the number of sensors that are needed. The increased particle collision rate in the future LHC-HL phase represents a great challenge for the Ring Imaging Cherenkov (RICH) photodetectors in the LHCb experiment. The LHCb collaboration is working for the Upgrade II that will take place during the Long Shutdown 4 of the LHC (>2032). The LAPPD produced and commercialised by INCOM (US) represents one of the possible alternatives for the future RICH photodetectors, thanks to its good time resolution, low dark noise rate and high gain. The LHCb Edinburgh group is involved in the Upgrade II R&D programme, testing and characterising an LAPPD in the laboratory of the University. The LAPPD technology, the current Edinburgh setup and performance from first tests of the photodetector will be presented.

Remote sensing oil in water with an all-fiber underwater single-photon Raman lidar.

The detection of oil in water is of great importance for maintaining subsurface infrastructures such as oil pipelines. As a potential technology for oceanic application, an oceanic lidar has proved its advantages for remote sensing of optical properties and subsea materials. However, current oceanic lidar systems are highly power-consuming and bulky, making them difficult to deploy underwater to monitor oil in water. To address this issue, we have developed a compact single-photon Raman lidar by using a single-photon detector with high quantum efficiency and low dark noise. Due to the single-photon sensitivity, the detection of the relatively weak Raman backscattered signal from underwater oil was realized with a laser with a pulse energy of 1µJ and a telescope with a diameter of 22.4mm. An experimental demonstration was conducted to obtain the distance-resolved Raman backscatter of underwater oil of different thicknesses up to a distance of 12m. The results indicate the single-photon Raman lidar's potential for inspecting underwater oil pipelines.

Solution-processed bismuth sulfide incorporated with zinc for high-gain and low-noise photodetection

Bismuth sulfide possesses an extremely high absorption coefficient, a relatively small bandgap, and high charge carrier mobility, which are favorable for photovoltaics and photodetection. However, the device performance of binary Bi2S3 is still limited by the poor charge transport and complicated trap features caused by the stoichiometric imbalance, as both sulfur vacancy and bismuth vacancy could result in tremendous trap states. In this work, we incorporate a small amount of extrinsic elements in the solution-processed Bi2S3 thin films and systematically investigate the influence of extrinsic doping on the charge transport properties of Bi2S3 thin films via time-resolved microwave conductivity and field-effect transistors. We also fabricate photodetectors based on these Zn2+ incorporated Bi2S3 thin films and achieve state-of-the-art device performance, including relatively high on/off ratio, high responsivity, and extremely low dark current and noise, which is promising for next-generation solution-processed photodetection.

Chalcogenide‐Based Narrowband Photodetectors for Imaging and Light Communication

AbstractChalcogenide‐based semiconductors have recently emerged as promising candidates for optoelectronic applications, mainly benefiting from their facile and low‐cost processability, chemical versatility, and tunable optoelectronic properties. Despite the recent success of chalcogenide‐based thin‐film photovoltaics, they have been barely leveraged in photodetection, mainly due to the complicated charge transport related to the trap states. In addition, most of the chalcogenide photodetectors are reported for broadband, visible photodetection, which is facile but lacks of impact for real applications. However, it is also possible to modulate the charge carrier dynamics of chalcogenide‐based materials, and devise novel devices, which can possess extra compelling features. These possibilities provide strong incentives for a detailed study on the chalcogenides‐based narrowband photodetectors, which are achieved by a filterless, charge collection narrowing strategy. The optimized narrowband photodetectors also exhibit extremely fast‐response (≈240 ns), relatively low dark current and noise, large linear dynamic range, and most importantly tunable spectral discrimination covering the whole range from UV to NIR. These devices also demonstrate great potential for imaging and communication.

Interfacial Engineering of High-Performance, Solution-Processed Sb2S3 Phototransistors.

Antimony sulfide, as a binary chalcogenide, has attracted great attention in the field of optoelectronics in recent years, particularly in photovoltaics, because of its striking merits such as earth elements abundance, excellent stability, chemical versatility, and solution processability. With the rapid development of fabrication techniques and device engineering, the device performance of Sb2S3 solar cells has experienced an unprecedented success. However, photodetectors based on Sb2S3 were barely reported, especially based on the transistor configuration. In this work, we prepared high quality Sb2S3 thin films via a sol-gel method, and Sb2S3 thin films were deposited on zinc-tin oxide based field-effect transistors. Furthermore, an additional electron transport layer was inserted between the Sb2S3 layers and the zinc-tin oxide channels and archived high-performance phototransistors with proper interfacial engineering. The optimized devices exhibited extremely high photosensitivity (106), low dark current (∼10 pA) and noise (∼11 fA Hz-1/2), high detectivity (1 × 1013 Jones), and superior device stability, indicating great potential for next generation solution-processed photodetectors.

Optoelectronic Modulation of Silver Antimony Sulfide Thin Films for Photodetection.

Silver antimony sulfide, as a ternary chalcogenide, has attracted great attention in the field of optoelectronics in recent years. In particular, it has appealing properties, such as excellent stability, solution processability, and versatile composition tunability. Benefiting from the recent development of processing techniques, AgSbS2 has emerged as a promising candidate for next-generation, thin-film photovoltaics. On the contrary, AgSbS2-based photodetectors have been barely reported. In this work, we systematically investigated the composition engineering of silver antimony sulfide compounds with a precursor route. Their optoelectronic properties were fully characterized, and the composition was optimized for photodetection. High-performance phototransistors were first reported based on field-effect thin film transistors with interfacial modification. The obtained AgSbS2 phototransistors exhibited relatively high photosensitivity, low dark current and noise, superior device stability, and excellent detectivity covering the whole range from ultraviolet to near-infrared, highlighting the great potential for next-generation photodetection.

Broadband spectral photodetector based on all-amorphous ZnO/Si heterostructure incorporating Ag intermediate thin-films

The purpose of the present work is to experimentally investigate a new high-performance broadband photodetector (PD) based on all-amorphous ZnO/Si heterostructure incorporating Ag ultrathin films. The sensor was developed using the RF magnetron sputtering method at room temperature conditions. In this context, a-ZnO/Ag/a-ZnO/a-Si/Ag/a-Si embedded ultrathin-films were sputtered on the glass substrate. The device structural, morphological, optical, and photodetection characteristics were studied by performing XRD, SEM, EDX, UV–Vis–NIR spectroscopy, and photoresponse characterizations. The analysis showed an improved absorbance behavior over a wide spectral range. It was demonstrated that the use of a-ZnO/a-Si heterostructure with Ag intermediate ultrathin-films incorporation leads to achieving multiband photodetection property with low dark noise effects, where the photodetector provides high responsivity values of 208 mA/W, 160 mA/W, and 180 mA/W over UV, Visible and NIR spectral ranges. These improvements are attributed to the combined effects of improved light-scattering due to the effect of agglomeration of silver on the surface, and the absorbance improvement enabled by optical micro-cavity effects generated by the inserted Ag ultrathin-films. Therefore, the present experimental study can offer new strategies for the development of highly-detective broadband multispectral photosensors based on a-Si photonics platform, which are suitable for optoelectronic applications.

Characterization of low light performance of a complementary metal-oxide semiconductor sensor for ultraviolet astronomical applications

Complementary metal-oxide semiconductor (CMOS) detectors offer many advantages over charge-coupled devices (CCDs) for optical and ultraviolet (UV) astronomical applications, especially in space where high radiation tolerance is required. However, astronomical instruments are most often designed for low light-level observations demanding low dark current and read noise, good linearity, and high dynamic range, characteristics that have not been widely demonstrated for CMOS imagers. We report the performance, over temperatures from 140 to 240 K, of a radiation hardened SRI 4k × 2k back-side illuminated CMOS image sensor with surface treatments that make it highly sensitive in blue and UV bands. After suppressing emission from glow sites resulting from defects in the engineering grade device examined, a 0.077 me − / s dark current floor is reached at 160 K, rising to 1 me − / s at 184 K, rivaling that of the best CCDs. We examine the trade-off between readout speed and read noise, finding that 1.43 e − median read noise is achieved using line-wise digital correlated double sampling at 700 kpix / s / ch corresponding to a 1.5 s readout time. The 15 ke − well capacity in high gain mode extends to 120 ke − in dual gain mode. Continued collection of photogenerated charge during readout enables a further dynamic range extension beyond 106 e − effective well capacity with only 1% loss of exposure efficiency by combining short and long exposures. A quadratic fit to correct for non-linearity reduces gain correction residuals from 1.5% to 0.2% in low gain mode and to 0.4% in high gain mode. Cross-talk to adjacent pixels is only 0.4% vertically, 0.6% horizontally, and 0.1% diagonally. These characteristics plus the relatively large (10 μm) pixel size, quasi 4-side buttability, electronic shutter, and sub-array readout make this sensor an excellent choice for wide field astronomical imaging in space, even at far-UV wavelengths where sky background is very low.

NEXO light detection system

nEXO is a future 5-tonne scale liquid xenon time projection chamber (TPC) experiment looking for hypothetical neutrinoless double beta decay of isotope 136Xe. To attain the projected half-life sensitivity of 1028 years, it aims to achieve an energy resolution of 1% or better at the Q-value (Qββ = 2.458 MeV) of the decay. nEXO plans to employ silicon photomultipliers (SiPMs) on the lateral surface of the cylindrical TPC to detect the light signals. Newly developed SiPMs sensitive to vacuum ultraviolet (VUV) light will be directly used for the detection of scintillation photons (λ = 175nm) in liquid xenon. For achieving the target energy resolution, the light detection system must have high photon detection efficiency, low correlated avalanche noise and low dark noise rate. The SiPM devices from two vendors are considered for the light detection system in the experiment. The primary goal of this research project is to characterize the VUV-SiPMs and measure their various features like gain, crosstalk, afterpulsing, dark noise rate, reflectivity and photon detection efficiency. Along with all these measurements, a monitoring tool will be required to test the large number of SiPMs before installing them in the detector. Current-voltage(IV) curve characterisation is being explored as a quick quality-testing tool for the performance of SiPM.

Squeezed light at 2128 nm for future gravitational-wave observatories

All gravitational-wave observatories (GWOs) have been using the laser wavelength of 1064 nm. Ultra-stable laser devices are at the sites of GEO 600, Kagra, LIGO, and Virgo. Since 2019, not only GEO 600, but also LIGO and Virgo have been using separate devices for squeezing the uncertainty of the light, so-called squeeze lasers. The sensitivities of future GWOs will strongly gain from reducing the thermal noise of the suspended mirrors, which involves shifting the wavelength into the 2 µm region. This Letter aims to reuse the existing high-performance lasers at 1064 nm. Here we report the realization of a squeeze laser at 2128 nm that uses pump light at 1064 nm. We achieve the direct observation of 7.2 dB of squeezing as the first step at megahertz sideband frequencies. The squeeze factor achieved is mainly limited by the photodiode's quantum efficiency, which we estimated to (92±3)%. Reaching larger squeeze factors seems feasible also in the required audio and sub-audio sideband, provided photo diodes with sufficiently low dark noise will be available. Our result promotes 2128 nm as the new, to the best of our knowledge, cost-efficient wavelength of GWOs.

High-Performance Organic Phototransistors Based on D18, a High-Mobility and Unipolar Polymer

Organic optoelectronics has progressed excitingly in recent years, mainly due to the innovation of donor and acceptor systems. Organic photodetectors based on novel semiconductor materials and well-designed device architectures have also been reported with improved device performance. However, most of them were photodiodes, and it is challenging to integrate them into the well-established readout circuits. Organic phototransistors are mainly based on the hybrid strategy, composed of either hybrid films or multilayer device structures, which complicates charge transfer and charge transport. Most of the organic devices also suffer from poor stability. In this work, we introduce a recently developed p-type copolymer, D18, to fabricate high-performance phototransistors. D18 possesses excellent charge generation, high mobility, and unipolar charge transport, which fulfill the generic design rule of organic phototransistors. The optimized phototransistors based on D18 exhibited extremely low dark current (∼10 pA) and noise (∼10 fA/Hz1/2), a high detectivity of 4 × 1013 Jones, a swift response of <5 ms, and excellent device stability. We also demonstrated flexible phototransistors with decent performance metrics, indicating great potential for next-generation solution-processed photodetectors and flexible electronic devices.

Emissive Charge-Transfer States at Hybrid Inorganic/Organic Heterojunctions Enable Low Non-Radiative Recombination and High-Performance Photodetectors.

Hybrid devices based on a heterojunction between inorganic and organic semiconductors have offered a means to combine the advantages of both classes of materials in optoelectronic devices, but, in practice, the performance of such devices has often been disappointing. Here, it is demonstrated that charge generation in hybrid inorganic-organic heterojunctions consisting of copper thiocyanate (CuSCN) and a variety of molecular acceptors (ITIC, IT-4F, Y6, PC70 BM, C70 , C60 ) proceeds via emissive charge-transfer (CT) states analogous to those found at all-organic heterojunctions. Importantly, contrary to what has been observed at previous organic-inorganic heterojunctions, the dissociation of the CT-exciton and subsequent charge separation is efficient, allowing the fabrication of planar photovoltaic devices with very low non-radiative voltage losses (0.21± 0.02V). It is shown that such low non-radiative recombination enables the fabrication of simple and cost-effective near-IR (NIR) detectors with extremely low dark current (4 pA cm-2 ) and noise spectral density (3 fA Hz-1/2 ) at no external bias, leading to specific detectivities at NIR wavelengths of just under 1013 Jones, close to the performance of commercial silicon photodetectors. It is believed that this work demonstrates the possibility for hybrid heterojunctions to exploit the unique properties of both inorganic and organic semiconductors for high-performance opto-electronic devices.

Post-annealing effects on RF sputtered all-amorphous ZnO/SiC heterostructure for solar-blind highly-detective and ultralow dark-noise UV photodetector

The rapid progress of wide band gap SiC semiconductor material opens up new opportunities to develop efficient monolithically integrated ultraviolet (UV) photonic and power systems for a wide range of advanced applications. In this paper, low-noise solar-blind UV photodetector (PD) based on all-amorphous ZnO/SiC heterostructure was fabricated via RF magnetron sputtering technique. The device structural and optical properties were investigated before and after thermal treatment at different annealing temperature values varying from 300 °C to 600 °C. UV-Visible spectroscopy revealed that the annealing process has a beneficial effect in terms of high UV absorbance and solar-blindness properties. Photoelectrical characterization demonstrated the high UV photoresponse and low dark noise of the prepared UV PD based on all-amorphous ZnO/SiC structure. Improvement of the device performances were achieved by an appropriate annealing process. After post-annealing, the thermally treated ZnO/SiC UV PD at 500 °C exhibits a high detectivity of 2.4 × 1012 Jones, high signal to noise ratio of 2.64×105 and a giant UV–Vis rejection ratio of 5.9 × 103. Therefore, the present study may provide new perspectives for fabricating ultralow dark noise solar-blind UV PD based on all-amorphous ZnO/SiC heterostructure, which promotes the development of integrated UV photonic systems based on SiC platform.

Imaging biological tissue with high-throughput single-pixel compressive holography

Single-pixel holography (SPH) is capable of generating holographic images with rich spatial information by employing only a single-pixel detector. Thanks to the relatively low dark-noise production, high sensitivity, large bandwidth, and cheap price of single-pixel detectors in comparison to pixel-array detectors, SPH is becoming an attractive imaging modality at wavelengths where pixel-array detectors are not available or prohibitively expensive. In this work, we develop a high-throughput single-pixel compressive holography with a space-bandwidth-time product (SBP-T) of 41,667 pixels/s, realized by enabling phase stepping naturally in time and abandoning the need for phase-encoded illumination. This holographic system is scalable to provide either a large field of view (~83 mm2) or a high resolution (5.80 μm × 4.31 μm). In particular, high-resolution holographic images of biological tissues are presented, exhibiting rich contrast in both amplitude and phase. This work is an important step towards multi-spectrum imaging using a single-pixel detector in biophotonics.