Near-infrared Light Detection Research Articles

Germanium-Incorporated Si-Ge-Si Heterojunction Phototransistors for High-Limit of Detection and Wide Linear Dynamic Range Near-Infrared Light Detection

Germanium-Incorporated Si-Ge-Si Heterojunction Phototransistors for High-Limit of Detection and Wide Linear Dynamic Range Near-Infrared Light Detection

Near-infrared detection based on the excitation of hot electrons in Au/Si microcone array

Although the photoresponse cut-off wavelength of Si is about 1100 nm due to the Si bandgap energy, the internal photoemission effect (IPE) of the Au/Si junction in Schottky detector can extend the absorption wavelength, which makes it a promising candidate for the Si-based infrared detector. However, due to low light absorption, low photon–electron interaction, and poor electron injection efficiency, the near-infrared light detection efficiency of the Schottky detector is still insufficient. The synergistic effect of Si nano/microstructures with a strong light trapping effect and nanoscale Au films with surface plasmon enhanced absorption may provide an effective solution for improving the detection efficiency. In this paper, a large-area periodic Si microcone array covered by an Au film has successfully been fabricated by one-time dry etching based on the mature polystyrene microspheres lithography technique and vacuum thermal deposition, and its properties for hot electron-based near infrared photodetection are investigated. Optical measurements show that the 20 nm-thick Au covered Si microcone array exhibits a low reflectance and a strong absorption (about 85%) in wide wavelength range (900–2500 nm), and the detection responsivity can reach a value as high as 17.1 and 7.0 mA W−1 at 1200 and 1310 nm under the front illumination, and 35.9 mA W−1 at 1310 nm under the back illumination respectively. Three-dimensional finite difference time domain (3D-FDTD) simulation results show that the enhanced local electric field in the Au layer distributes near the air/Au interface under the front illumination and close to the Au/Si interface under the back illumination. The back illumination favors the injection of photo-generated hot electrons in Au layer into Si, which can explain the higher responsivity under the back illumination. Our research is expected to promote the practical application of Schottky photodetectors to Si-compatible near infrared photodetectors.

Short-wavelength infrared light sensing using an electrostatic MEMS resonator integrated with a plasmonic optical absorber

Near-infrared light detectors are employed in various fields such as food inspection for spectroscopic measurements. Despite the fact that photodiodes made of compound semiconductors are used in conjunction with optical filters or monochromators for highly sensitive and wavelength-selective detection of near-infrared light, improvements in device size and cost are necessary for widespread application. Therefore, we propose the use of silicon microelectromechanical systems (MEMS) sensors. This study proposes a single-crystalline Si electrostatic MEMS resonator sensor that is integrated with a gold nanostructure near-infrared light absorber. The device utilizes the resonance frequency shift that occurs due to the thermal stress caused by the heat generated by the near-infrared light on the resonator. A gold nanostructure absorber is mounted on the resonator to enhance photothermal conversion efficiency, enabling the detection of near-infrared light with wavelength selectivity. We fabricated an Au nanostructure-mounted electrostatic transducer and evaluated its performance by measuring its resonance under near-infrared light irradiation. In a light intensity detection experiment, it was found that the relative resonant frequency shift increased linearly with the input in the range below 100 μW, which is consistent with the trend against the input heat. The minimum detection resolution of the light intensity was approximately 5 nW, and the minimum detectable intensity was 3.8 nW. The linear relationship between the optical absorption coefficient and the relative resonance frequency shift was clarified. An array of the devices with different absorption wavelength bands can be used to realize an ultra-compact spectroscopic analysis device without the need for traditional optical filters or monochromators.

Room temperature electrical characteristics of gold-hyperdoped silicon

Hyperdoped silicon is a promising material for near-infrared light detection, but to date, the device efficiency has been limited. To optimize photodetectors based on this material that operate at room temperature, we present a detailed study on the electrical nature of gold-hyperdoped silicon formed via ion implantation and pulsed-laser melting (PLM). After PLM processing, oxygen-rich and gold-rich surface layers were identified and a wet etch process was developed to remove them. Resistivity and Hall effect measurements were performed at various stages of device processing. The underlying gold-hyperdoped silicon was found to be semi-insulating, regardless of whether the surface gold was removed by etching or not. We propose a Fermi level pinning model to describe the band bending of the transformed surface layer and propose a promising device architecture for efficient Au-hyperdoped Si photodetectors.

Colorful visualization detection of near-infrared light enabled by an upconversion device with a color-tunable quantum dot light-emitting unit

Color-tunable near-infrared (NIR)-to-visible upconversion devices (UCDs) that correlate the NIR power intensity with the visible emission color are highly desired and hold promise for interactive signal visualization in intelligent optoelectronic devices. In this work, solution-processed color-tunable UCDs integrating a NIR sensing photodetector unit and a color-tunable quantum dot (QD) light-emitting unit are demonstrated. We mixed the red and green QDs in a single emissive layer (EML) for multi-color emission from the UCDs, which is quite different from the previously reported work that used multiple EMLs with different colors. The image color of the resulting color-tunable UCDs can be modulated by bias voltage and driving current and shows a wide color-span range from red to green as the NIR intensity increases. Finally, we present a qualitative correlation between the incident NIR power intensity and the visible emission color, which enables colorful visualization detection of NIR light.

Efficient charge separation and improved photoelectric properties of GaN/WS2/MoS2 heterojunction: A molecular dynamics simulations

Utilizing the stacking of two-dimensional (2D) materials to fabricate heterojunction represents an exceedingly effective approach for designing high-performance optoelectronic devices. In this paper, the GaN/WS2/MoS2 heterojunction was systematically studied using DFT calculations. The interface effect caused the effective separation of photo-excited carriers in the GaN/WS2/MoS2 heterojunction by inducing a stepwise transfer of the carriers, forming a build-in electric field. Due to the decrease in bandgap, the heterojunction exhibited enhanced light absorption ability across the entire spectral region. Especially, the carrier recombination time reached the microsecond level, greatly extending the lifetime of photo-excited carriers and effectively improving the energy conversion performance of photodetectors. Moreover, the augmentation of tensile strain enhances both the self-powering capacity and the near-infrared light detection capability of the GaN/WS2/MoS2 heterojunction. The exceptional performances exhibited by the GaN/WS2/MoS2 heterojunction make it a highly up-and-coming candidate for optoelectronics application.

Design and Fabrication of Broadband InGaAs Detectors Integrated with Nanostructures.

A visible-extended shortwave infrared indium gallium arsenide (InGaAs) focal plane array (FPA) detector is the ideal choice for reducing the size, weight and power (SWaP) of infrared imaging systems, especially in low-light night vision and other fields that require simultaneous visible and near-infrared light detection. However, the lower quantum efficiency in the visible band has limited the extensive application of the visible-extended InGaAs FPA. Recently, a novel optical metasurface has been considered a solution for a high-performance semiconductor photoelectric device due to its highly controllable property of electromagnetic wave manipulation. Broadband Mie resonator arrays, such as nanocones and nanopillars designed with FDTD methods, were integrated on a back-illuminated InGaAs FPA as an AR metasurface. The visible-extended InGaAs detector was fabricated using substrate removal technology. The nanostructures integrated into the Vis-SWIR InGaAs detectors could realize a 10-20% enhanced quantum efficiency and an 18.8% higher FPA response throughout the wavelength range of 500-1700 nm. Compared with the traditional AR coating, nanostructure integration has advantages, such as broadband high responsivity and omnidirection antireflection, as a promising route for future Vis-SWIR InGaAs detectors with higher image quality.

NIR-UV Dual-Mode Photodetector with the Assistance of Machine-Learning Fabricated by Hybrid Laser Processing

Photodetectors are widely used in optoelectronic applications such as remote controlling, optical communication, and intelligent manufacturing. Multi-wavelength response capability can expand the application scenarios of a photodetector. However, responding to and recognizing multiple bands is still challenging for a photodetector. Here, we develop a dual-mode photodetector that can respond to and recognize near-infrared (NIR) and ultraviolet (UV) light with the assistance of a machine-learning model. A hybrid laser processing method was proposed to fabricate this photodetector based on the polyimide substrate. This method uses femtosecond laser and continuous wave laser to induce the formation of carbon and zinc oxide composite material in different forms. The femtosecond laser-processed area and the continuous wave laser-processed area realized stable NIR light detection and UV light detection, respectively. Recognition of the type of incident light was realized with the assistance of a machine-learning classification model. The proposed hybrid laser processing method combines the characteristics of two kinds of lasers and provides new insights into fabricating dual-mode photodetector. This photodetector could advance the development of dual-mode photodetection and has application potential in many fields like wearable devices and smart clothing.

High-temperature phonon-assisted upconversion photoluminescence of monolayer WSe2

Phonon-assisted upconversion photoluminescence (UPL) is an anti-Stokes process emitting photons of energy higher than the excitation photons, with upconversion energy gain provided by optical phonons. Atomically thin transition metal dichalcogenides provide a promising platform for exploring the phonon-assisted UPL process due to their strong phonon–exciton interactions. Here, high-temperature phonon-assisted UPL process in monolayer WSe2 is investigated, aiming to understand the role of phonon population and the number of phonons involved in the UPL process at elevated temperatures. It is demonstrated that the integrated intensity of UPL emission significantly increases by two orders of magnitude as the temperature rises from room temperature of 295 to 476 K, which is distinguished from the photoluminescence emission usually suffering from thermal quenching. The observed growth of UPL emission intensity is attributed to both the increased phonon population and the reduced number of phonons required at elevated temperatures. Our study paves the way toward near-infrared light detection, anti-Stokes energy harvesting, optical refrigeration, and temperature sensing.

Free-standing [0 0 1]-oriented one-dimensional crystal-structured antimony selenide films for self-powered flexible near-infrared photodetectors

Flexible optoelectronic is one of the key components for acquiring biological signals in wearable devices and implantable systems. Recently, antimony selenide (Sb2Se3) has shown an exciting potential for flexible optoelectronic applications due to its unique one-dimensional (1D) ribbon-typed crystal structure, low-cost constituents, and superior optoelectronic properties. However, the growth of [001]-oriented Sb2Se3 film, which can efficiently enhance the carrier transport, is still challenging, particularly for its application in flexible electronics. Herein, we propose to grow the free-standing [001]-oriented Sb2Se3 film for self-powered flexible photodiode through selenizing the highly (0001)-textured Sb film on mica substrate. The theoretical calculation reveals that Sb(0001) plane provides a high adsorption energy for Se atoms, which promotes the [001]-oriented growth of Sb2Se3 film. The weak vdW interaction between Sb2Se3 film and mica substrate enables the film separation, and results in a free-standing Sb2Se3 film. Benefiting from the enhanced carrier transport in [001]-oriented Sb2Se3 film, the flexible photodiode exhibits a high responsivity up to 0.74 A W−1, a specific detectivity of 5.1 × 1013 Jones, a linear dynamic range of 102 dB, rise/fall time of 0.16/0.15 ms for near-infrared light detection without any external bias, and excellent folding endurance after 1000 bending cycles. It has been also successfully employed as a wearable photodetector to detect a person’s heart rate. This work demonstrates a strategy for the orientation control of low-dimensional crystal-structured materials and a great potential of free-standing films in flexible electronics applications.

Structural, electronic and optical properties of fluorinated bilayer silicene

Silicon (Si) is undoubtedly an excellent material for electronic applications. However, Si is not a suitable material for optoelectronic applications due to its indirect bandgap. Based on the first principles approach, we have studied different stacking (AA and AB) patterns in bilayer silicene. The phonon band structure of AA and AB-stacked “bilayer silicene” reveals that only AB-stacked silicene is stable. Different fluorinated configurations (1F, 2F, 3F and 4F) of AB-stacked bilayer silicene are analyzed in terms of structural parameters and the phonon band structure. Of the four fluorinated configurations, 2F-AB-stacked bilayer silicene has a direct bandgap of 1.23 eV. The direct bandgap allows the carriers to transit from the “valence band” to the “conduction band” with a low probability of phonon generation. Meanwhile, the other configurations either lack stability or have a zero bandgap. The proposed fluorinated bilayer silicene, in addition to having an expected integration with silicon technology, could also be suitable for visible and near-infrared light detection applications.

PCE10 Significantly Improves Red and Near-infrared Light Detection Capabilities of Ternary Photomultiplication-type Organic Photodetectors

PCE10 Significantly Improves Red and Near-infrared Light Detection Capabilities of Ternary Photomultiplication-type Organic Photodetectors

Development of single photon avalanche detectors for NIR light detection

Near-infrared (NIR) light is used in several non-invasive biomedical techniques to measure the blood flow in deep tissues. The BIOSPAD project targets the development of SPAD arrays specifically designed for Diffuse Correlation Spectroscopy (DCS) in the NIR to measure deep tissue microvascular blood flow. In the first stage of the project, single SPADs with multiplication layers buried at different depths have been designed at IFAE and produced in a 150 nm CMOS technology. In this study, we present results of the characterization of SPAD devices with an area of 50 × 50 µm2 operated with an external passive quenching circuit. We compared properties, such as Dark Count Rate (DCR) and Photon Detection Efficiency (PDE) of the different SPAD designs. The PDE for 780 nm light of SPADs with a buried multiplication layer was observed to be in the range of 10–20% with a DCR of the order of 2 kHz. The results of these first prototypes are promising and are being followed up by the development of a new generation of CMOS SPADs designed to further improve the NIR light response.

In Situ Growth of PbS/PbI2 Heterojunction and Its Photoelectric Properties.

In this paper, PbI2 thin films with a uniform surface morphology and compact structure were prepared by adjusting the spin coating process parameters. On such a basis, the PbS/PbI2 heterojunction was fabricated on the PbI2 surface by the method of in situ chemical replacement growth. The results show that the PbS/PbI2 heterojunction grown by this method has a clear interface and is closely combined. The introduction of a PbS layer enables its spectral response range to cover the visible and near-infrared regions. Compared with the PbI2 thin film device, its responsivity is increased by three orders of magnitude, its response time reduced by 42%, and its recovery time decreased by nearly 1/2 under 450 nm illumination. In the case that there is no response for the PbI2 thin film device under 980 nm illumination, the specific detectivity of the PbS/PbI2 heterojunction device still amounts to 1.8 × 108 Jones. This indicates that the in situ chemical replacement is a technique that can construct a high-quality heterojunction in a simple process. PbS/PbI2 heterojunction fabricated by this method has a visible–near-infrared light detection response range, which provides a new idea for creating visible–near-infrared common-path detection systems.

Near infrared emitting Cr3+ doped Zn3Ga2Ge2O10 long persistent phosphor for night vision surveillance and anti-counterfeit applications

The Cr3+ doped Zn3Ga2Ge2O10 long persistent phosphor materials were synthesized by solid state reaction method. The crystal structure of the synthesized phosphors are cubic with space group Fd3m. The band gap of the undoped host is about 4.48 eV. The materials show three photoluminescence excitation bands peaked at 260 nm, 412 nm and 580 nm. Due to the broad excitation band, the phosphors can be excited by UV light or visible light or sunlight. The phosphors shows a photoluminescence emission band peaked at 698 nm when excited by UV light. The afterglow emission shows a broad emission band with maximum at 700 nm. The detection of NIR light from the sample was observed by Night Vision Monocular for 24 h after switch off the excitation source. A mechanism is introduced to describe afterglow phenomenon and trap depth was calculated from thermoluminescence curve. As the material emit NIR persistent light, it was used as a secret light source for night vision devices. The developed material was used for tagging, tracking and locating purposes in defence application. The acrylic based paint was prepared to develop long persistent near infrared (NIR) paint, which can be coated on combat vehicle, ship, weapon, helmet, cloth, tent, rock for defence application. The NIR security ink was prepared and demonstrated to prevent counterfeit. Encryption and decryption method of confidential information was presented by using NIR security ink.

A Near-Infrared CMOS Silicon Avalanche Photodetector with Ultra-Low Temperature Coefficient of Breakdown Voltage.

Silicon avalanche photodetector (APD) plays a very important role in near-infrared light detection due to its linear controllable gain and attractive manufacturing cost. In this paper, a silicon APD with punch-through structure is designed and fabricated by standard 0.5 μm complementary metal oxide semiconductor (CMOS) technology. The proposed structure eliminates the requirements for wafer-thinning and the double-side metallization process by most commercial Si APD products. The fabricated device shows very low level dark current of several tens Picoamperes and ultra-high multiplication gain of ~4600 at near-infrared wavelength. The ultra-low extracted temperature coefficient of the breakdown voltage is 0.077 V/K. The high performance provides a promising solution for near-infrared weak light detection.

Photocurrent Enhancement of PtSe2 Photodetectors by Using Au Nanorods

Compact and highly sensitive near-infrared photodetectors that are operable at room temperature are required for light detection and ranging and medical devices. Two-dimensional (2D) PtSe2, a transition metal dichalcogenide, is a candidate material for near-infrared light detection. However, the photoresponse properties of 2D PtSe2 are currently inferior to those of commercial materials. The localized surface plasmon resonance of Au has been widely used for photoelectric field enhancement and in photochemical reactions associated with phase relaxation from plasmon states that occur at specific wavelengths. Spherical Au nanocolloids exhibit an extinction peak in the visible light region, whereas nanorods can be tuned to exhibit the extinction peak in the near-infrared region by controlling their aspect ratio. In this study, hybrid Au nanorod/2D PtSe2 structure was fabricated via spin coating nanorods, with plasmon peaks in the near-infrared region, on 2D PtSe2. Furthermore, the effect of the concentration of the nanorod solution on the photoresponse of nanorod/2D PtSe2 was investigated. The photocurrent of 5 nM Au nanorod-coated 2D PtSe2 was fivefold higher than that of bare 2D PtSe2. The responsivity was maximum 908 μW/A at 0.5 V bias voltage. In addition, the photocurrent enhancement mechanism by Au nanorods is discussed.

Cheap and green deep eutectic solvents with favorable physical properties for significantly improved near-infrared light detection

Cheap and highly thermal-sensitive liquid media with favorable physical properties is one of the key parameters for achieving the efficient near-infrared light (NIR) photothermal sensor with high potential application. However, the reported liquid media for photothermal sensor is expensive or non-efficient. Herein, several deep eutectic solvents (DESs) composed by DBU and LiNO3 with different mole ratio are utilized as liquid media and DBU:LiNO3 (3:1) shows the best thermal-sensitive ability. After doping photothermal agents polydopamine (PDA) with DBU:LiNO3 (3:1), the efficiency of photothermal sensor could reach 1100.25%, much higher than the highest value of the previous report (ca. 379.91%) at the same NIR light power. Cycle investigation on the NIR photothermal sensor could be recycled at least five times with negligible loss of efficiency. Most importantly, the price of DBU:LiNO3 (3:1) in this work is also about one third of the previous report. This work broadens the design strategy for highly efficient NIR photothermal sensor through selecting appropriate component and regulating suitable mole ratio of DESs with low cost and high sustainability.

Self-powered flexible artificial synapse for near-infrared light detection

In the era of artificial intelligence, photonic artificial synapses that are capable of light detection and information storage are attracting much attention, although complex device configuration and high energy consumption are two remaining challenges. Here, a flexible polymer-based optical synapse for infrared light detection in the absence of applied voltage is fabricated to emulate human synaptic photoplasticity. Investigation into the mechanism of the self-powered properties demonstrates that both the localized electric field of the polyethylene terephthalate (PET) substrate and the high dielectric constant of narrow-band conjugated polymer contribute to spontaneous exciton dissociation. Moreover, array imaging and data encryption are achieved by modulating light for the flexible devices, which exhibit excellent mechanical flexibility and long-term air stability. Thus, this work may provide a strategy to develop self-powered artificial synapses for infrared light detection. Short-wavelength infrared light-responsive organic synapse Self-powered flexible photonic synapse with two-terminal device structure Polymer with dielectric constant as high as 5.8 Visual memory array imaging and encryption model application for near-infrared light To mimic the human visual system, Chen et al. adopt organic materials to sense and memorize light, including infrared light. The simple device can operate without voltage, and the strategy may provide sustainable energy solutions for artificial intelligence applications.

Energy-Level Manipulation in Novel Indacenodithiophene-Based Donor–Acceptor Polymers for Near-Infrared Organic Photodetectors

Organic photodetectors (OPDs) are promising candidates for next-generation digital imaging and wearable sensors due to their low cost, tuneable optoelectrical properties combined with high-level performance, and solution-processed fabrication techniques. However, OPD detection is often limited to shorter wavelengths, whereas photodetection in the near-infrared (NIR) region is increasingly being required for wearable electronics and medical device applications. NIR sensing suffers from low responsivity and high dark currents. A common approach to enhance NIR photon detection is lowering the optical band gap via donor-acceptor (D-A) molecular engineering. Herein, we present the synthesis of two novel indacenodithiophene (IDT)-based D-A conjugated polymers, namely, PDPPy-IT and PSNT-IT via palladium-catalyzed Stille coupling reactions. These novel polymers exhibit optical band gaps of 1.81 and 1.27 eV for PDPPy-IT and PSNT-IT, respectively, with highly desirable visible and NIR light detection through energy-level manipulation. Moreover, excellent materials' solubility and thin-film processability allow easy incorporation of these polymers as an active layer into OPDs for light detection. In the case of PSNT-IT devices, a photodetection up to 1000 nm is demonstrated with a peak sensitivity centered at 875 nm, whereas PDPPy-IT devices are efficient in detecting the visible spectrum with the highest sensitivity at 660 nm. Overall, both OPDs exhibit spectral responsivities up to 0.11 A W-1 and dark currents in the nA cm-2 range. With linear dynamic ranges exceeding 140 dB and fast response times recorded below 100 μs, the use of novel IDT-based polymers in OPDs shows great potential for wearable optoelectronics.