Multispectral Photodetectors Research Articles

Self-Powered Multispectral Photodetectors for High-Fidelity Weak-Light Panchromatic Imaging

Self-Powered Multispectral Photodetectors for High-Fidelity Weak-Light Panchromatic Imaging

Programmable, High-resolution Printing of Spatially Graded Perovskites for Multispectral Photodetectors.

Micro/nanostructured perovskites with spatially graded compositions and bandgaps are promising in filter-free, chip-level multispectral, and hyperspectral detection. However, achieving high-resolution patterning of perovskites with controlled graded compositions is challenging. Here, a programmable mixed electrohydrodynamic printing (M-ePrinting) technique is presented to realize the one-step direct-printing of arbitrary spatially graded perovskite micro/nanopatterns for the first time. M-ePrinting enables in situ mixing and ejection of solutions with controlled composition/bandgap by programmatically varying driving voltage applied to a multichannel nozzle. Composition can be graded over a single dot, line or complex pattern, and the printed feature size is down to 1µm, which is the highest printing resolution of graded patterns to the knowledge. Photodetectors based on micro/nanostructured perovskites with halide ions gradually varying from Br to I are constructed, which successfully achieve multispectral detection and full-color imaging, with a high detectivity and responsivity of 3.27 × 1015 Jones and 69.88 A W-1, respectively. The presented method provides a versatile and competitive approach for such miniaturized bandgap-tunable perovskite spectrometer platforms and artificial vision systems, and also opens new avenues for the digital fabrication of composition-programmable structures.

Sputtering-grown undoped GeSn/Ge multiple quantum wells on n-Ge for low-cost visible/shortwave infrared dual-band photodetection

Multispectral photodetectors (PDs) operating in visible (VIS) to shortwave infrared (SWIR) wavelength ranges are highly desired for various civil and military applications. Traditional vertical p-i-n SWIR PDs lack the detection ability for VIS light due to photon dissipation in the neutral regions. Herein, an i-n type PD was proposed and demonstrated with sputtering-grown undoped Ge0.92Sn0.08/Ge multiple quantum wells (MQWs) on n-Ge substrate to realize VIS/SWIR dual-band detection from 400 to 2000 nm. Three response peaks resulted from the resonate cavity effect at 430, 660 and 1530 nm, respectively, were observed. Benefiting from the defect-free coherent GeSn/Ge MQWs and low-temperature surface plasma treatment, a remarkably low bulk leakage current density of 5.9 mA/cm2 and a low surface leakage current of 37.5 μA/cm were achieved at room temperature under −1 V, resulting in an ultralow dark current density of 13.36 mA/cm2 for a 200-μm-diameter PD. Temperature-dependent electrical characterizations revealed that the dark current was ideally dominated by carrier diffusion mechanism. Eminent detectivities of 5.2 × 108, 7.1 × 108 and 5.6 × 109 Jones at 410, 660 and 1530 nm, respectively, under −1 V were achieved simultaneously at room temperature. This work provides a path way for fabricating low-cost, VIS/SWIR dual-band PDs with complementary metal–oxide–semiconductor (CMOS) compatible technology.

Photosensitive Dielectric 2D Perovskite Based Photodetector for Dual Wavelength Demultiplexing.

Stacked 2D perovskites provide more possibilities for next generation photodetector with more new features. Compared with its excellent optoelectronic properties, the good dielectric performance of metal halide perovskite rarely comes into notice. Here, a bifunctional perovskite based photovoltaic detector capable of two wavelength demultiplexing is demonstrated. In the Black Phosphorus/Perovskite/MoS2 structured photodetector, the comprehensive utilization of the photosensitive and dielectric properties of 2D perovskite allows the device to work in different modes. The device shows normal continuous photoresponse under 405 nm, while it shows a transient spike response to visible light with longer wavelengths. The linear dynamic range, rise/decay time, and self-powered responsivity under 405nm can reach 100, 38 µs/50 µs, and 17.7mA W-1 , respectively. It is demonstrated that the transient spike photocurrent with long wavelength exposure is related to the illumination intensity and can coexist with normal photoresponse. Two waveband-dependentsignals can be identified and used to reflect more information simultaneously. This work provides a new strategy for multispectral detection and demultiplexing, which can be used to improve data transfer rates and encrypted communications. This work mode can inspire more multispectral photodetectors with different stacked 2D materials, especially to the optoelectronic application of the wide bandgap, high dielectric photosensitive materials.

Controllable bandgap-gradient halide perovskite films via dip-coating and halide anion exchange for multispectral photodiodes with high performance

Multispectral photodetectors based on one-dimensional bandgap-gradient halide perovskite films by combining dip-coating and halide anion exchange show continuously varying response cutoff band edges and a high Ion/Ioff of 104–106.

Multispectral and Circular Polarization-Sensitive Carbon Dot-Polydiacetylene Capacitive Photodetector.

Multispectral photodetectors (MSPs)and circularly polarized light (CPL) sensors are important in opto-electronics, photonics, and imaging. A capacitive photodetector consisting of an interdigitated electrode coated with carbon dot/anthraquinone-polydiacetylene is constructed. Photoexcitation of the carbon dots induces transient electron transfer to the anthraquinone moieties, and concomitant change in the film dielectric constant and recorded capacitance. This unique photodetection mechanism furnishes wavelength selectivity that is solely determined by the absorbance of the carbon dots incorporated in the anthraquinone-polydiacetylene matrix. Accordingly, employing an array of polymerized-anthraquinone photodetector films comprising carbon dots (C-dots)exhibiting different excitation wavelengths yielded optical "capacitive fingerprints" in a broad spectral range (350-650nm). Furthermore, circular light polarization selectivity is achieved through chiral polymerization of the polydiacetylene framework. The carbon dot/anthraquinone-polydiacetylene capacitive photodetector features rapid photo-response, high fidelity, and recyclability as the redox reactions of anthraquinone are fully reversible. The carbon dot/anthraquinone-polydiacetylene platform is inexpensive, easy to fabricate, and consists of environmentally friendly materials.

Flexible Miniaturized Multispectral Detector Derived from Blade-Coated Organic Narrowband Response Unit Array.

Multispectral sensing is extremely desired in intelligent systems, e.g., autonomous vehicles, encrypted information communication, and health biometric monitoring, due to its highly sensitive spectral discrimination ability. Nevertheless, rigid bulky optics and delicate optical paths in devices significantly increase their complexity and size, which subsequently impede their integration in smart optoelectronic chips for universal applications. In this work, a filterless miniaturized multispectral photodetector is realized with an organic narrowband response unit array. With the manipulation of Frenkel exciton dissociation in active layers, a series of narrowband organic sensing units with full-width-at-half-maximum (fwhm) narrowing to ∼50 nm are achieved from 700 to 1050 nm with a laudable performance of responsivity of over 60 mA/W, -3 dB bandwidth over 10 kHz, linear dynamic range (LDR) reaching ∼120 dB, and a low noise current of less than 4 × 10-14 A·Hz-0.5. Furthermore, a 6 × 8 multispectral sensing array on a flexible substrate was fabricated with blade-coating. Assisted by a computational process, we successfully demonstrate the spectral recognition with a resolution of ∼50 nm and a mismatch of ∼10 nm. Finally, the function of matter identification is successfully achieved with our multispectral detector array.

Compact multispectral photodetectors based on nanodisk arrays atop optical cavity substrates.

It is challenging for the multi-spectral photodetector to have a compact structure, high spectral resolution, and high detection efficiency. This paper reports on a new approach for compact multi-spectral visible light detecting based on the hexagonal lattice silver nanodisk arrays atop optical cavity substrates. Through numerical calculations and optimizations of experiments, we verified that the narrow band responsivity of the photodetector was caused by coupling the surface plasmonic resonances and cavity mode. The multi-spectral photodetector exhibited that the minimum FWHM and the maximum responsivity of was achieved to be 80 nm and 91.5 mA·W-1, respectively. Besides, we also analyzed the influence of the proposed structure on the energy wastage by numerical comparison. The proposed way for multi-spectral photodetector is promising to be an excellent design for the narrow band spectral detection. The design can also be easily integrated with CMOS devices and applied to other spectral regimes for different applications.

Wavelength-Tunable Multispectral Photodetector With Both Ultraviolet and Near-Infrared Narrowband Detection Capability

The development of high-performance multispectral photodetector with narrowband and tunable spectral sensitivity is of importance but remains highly challenging to date. Here, we have reported on the fabrication of a Si Au/n-type Si/Au photodetector with tunable narrowband sensitivity not only in ultraviolet but also in near-infrared region, which is related to the controlled charge collection narrowing (CCN) mechanism. What is more, the negative response peak of the device can be readily tuned from 365 to 605 nm, and the positive response peak can be modulated from 938 to 970 nm when the bias varies from 0.1 to −0.1 V. In particular, the full-width at half-maximum is as small as 92 and 117 nm when the negative and positive response peaks approach the ultraviolet short wavelength end and near-infrared long wavelength end, respectively. The opposite polarity of the device responses in ultraviolet-visible and near-infrared regions renders the present Si photodetector potentially important in future multiple band optoelectronic systems.

Monolithic RGB-NIR Perovskite Photodetector for Fused Multispectral Sensing and Imaging.

The multispectral fusion of near-infrared (NIR) and visible red-green-blue (RGB) photons can enhance target identification under weak light conditions. Nevertheless, the crosstalk between NIR and RGB photons in a traditional pixelated sensor impedes their practical application, while using complex algorithms and optical filters would significantly increase the cost, form factor, and frame latency. In this work, a delicate monolithic RGBN (RGB-NIR) multispectral photodetector (PD) is proposed on the basis of perovskite materials without complicated algorithms or optical filters. The multispectral response toward selective RGBN signals in this monolithic PD pixels can be achieved by switching the polarity of the applied bias, affording the following benefits: Ion/Ioff ratio of >104, detectivity of >1010 Jones, crosstalk of -74 dB, and fast response with -3 dB > 103 Hz. Moreover, proof-of-concept imaging of the iris and periocular with successful recognition in multispectral fusion further confirms its potential for identity authentication.

Multi-Bandgap Monolithic Metal Nanowire Percolation Network Sensor Integration by Reversible Selective Laser-Induced Redox

HighlightsA three single-phase Cu, Cu2O, and CuO monolithic nanowire network was successfully fabricated by reversible selective laser-induced redox (rSLIR)Monolithic metal–semiconductor–metal multispectral photodetectors with Cu nanowire (CuNW) as an electrode and Cu2ONW/CuONW having different bandgaps were suggested.

Dual-color charge-sensitive infrared phototransistors with dynamic optical gate

Infrared multispectral photodetectors with high performance show great potential in a broad range of applications. Here, sensitive and controllable dual-color photodetection at 10.6 and 15.7 μm is demonstrated by using a charge sensitive infrared phototransistor (CSIP) with dynamical optical gate. The CSIP device is fabricated in a GaAs/AlGaAs double quantum well (QW) crystal with both upper and lower QWs (7 and 11 nm thick, respectively) being photosensitive via intersubband absorption and, hence, each QW corresponding to one target wavelength (10.6 and 15.7 μm, respectively). Moreover, the upper QW serves as a photosensitive floating gate (FG), while the lower QW functions as the conducting channel of the phototransistor. By periodically lifting-up (lowering-down) the electrostatic potential of FG, the photoresponse at 10.6 (15.7 μm) associated with photoexcitation in upper (lower) QW can be achieved. This electrically controllable photoresponse together with intrinsically high photoconductive gain (∼102) provides a scheme to realize sensitive dual-color photodetection for infrared optoelectronic applications.

Broadband GaAsSb Nanowire Array Photodetectors for Filter-Free Multispectral Imaging.

Highly compact, filter-free multispectral photodetectors have important applications in biological imaging, face recognition, and remote sensing. In this work, we demonstrate room-temperature wavelength-selective multipixel photodetectors based on GaAs0.94Sb0.06 nanowire arrays grown by metalorganic vapor phase epitaxy, providing more than 10 light detection channels covering both visible and near-infrared ranges without using any optical filters. The nanowire array geometry-related tunable spectral photoresponse has been demonstrated both theoretically and experimentally and shown to be originated from the strong and tunable resonance modes that are supported in the GaAsSb array nanowires. High responsivity and detectivity (up to 44.9 A/W and 1.2 × 1012 cm √Hz/W at 1 V, respectively) were obtained from the array photodetectors, enabling high-resolution RGB color imaging by applying such a nanowire array based single pixel imager. The results indicate that our filter-free wavelength-selective GaAsSb nanowire array photodetectors are promising candidates for the development of future high-quality multispectral imagers.

Multispectral photodetectors based on 2D material/Cs3Bi2I9 heterostructures with high detectivity

Group VA metal halide-based perovskites have emerged as intensively explored Pb-free perovskites, owing to their excellent environmental stability and low-toxicity. However, the relatively low carrier mobility and high photocarrier recombination rates restrict their applications in photodetectors. One promising approach to achieve higher performance is to integrate these Pb-free perovskites with 2D materials to form heterostructures. Here, we report on the high sensitivity photodetectors based on MoS2/Cs3Bi2I9 and graphene/Cs3Bi2I9 heterostructures for multispectral regions. The heterostructures combine the high carrier mobility of 2D materials with superior light-harvesting properties of perovskites, as well as the effective built-in electric filed at the junction area, leading to efficient photocarrier separation and extraction. The specific detectivity of MoS2/Cs3Bi2I9 device reaches 1.15 × 1013 Jones for the detection of ultraviolet (UV) light of 325 nm, which is four orders of magnitude higher than UV detectors built on GaN. As a result of the efficient dark current suppression, the specific detectivity of graphene/Cs3Bi2I9 photodetector can be promoted to 5.24 × 1011 Jones, 1.33 × 1011 Jones, and 1.12 × 1011 Jones for the detection of 325 nm, 447 nm, and 532 nm light, respectively.

Highly efficient and low-cost multispectral photodetector based on RF sputtered a-Si/Ti multilayer structure for Si-photonics applications

In this paper, a new cost-effective multispectral photodetector (PD) based on amorphous-silicon (a-Si)/titanium (Ti) multilayer structure, which achieves a high UV-Visible-NIR photoresponse is elaborated. A new design strategy based on combining FDTD (Finite Difference Time Domain) with GA (Genetic Algorithm) was used to determinate the a-Si/Ti multilayer geometry providing the highest photoresponsivity in UV, Visible and NIR regions. The optimized structure is then fabricated using RF magnetron sputtering technique. A comprehensive analysis of the photodetector electrical, optical and structural properties was carried out. The sputtered a-Si/Ti multilayer was characterized by Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), and UV–visible-NIR absorption spectroscopy. The a-Si/Ti multilayer PD exhibits a high broadband absorbance of 80% over the UV and even NIR spectrum ranges [200–1100 nm]. Moreover, photoelectrical characterization showed that the developed device exhibits an improved responsivity under UV, Visible and NIR lights (1.9 A/W at 365 nm, 1.24 A/W at 550 nm and 0.93 A/W at 900 nm) and a high ION/IOFF ratio of 68 dB. The broadband multispectral photodetection property offered by the proposed a-Si/Ti multilayer PD opens a new route for the fabrication of promising alternative photodetectors for future high-performance and cost-effective optoelectronic systems.

Multispectral photodetection using low-cost sputtered NiO/Ag/ITO heterostructure: From design concept to elaboration

High-performance multispectral photodetectors (PDs) are highly attractive for the emerging optoelectronic applications. In this work, a new broadband PD based on p-NiO/Ag/n-ITO heterostructure was fabricated by RF magnetron sputtering technique at room temperature. The tri-layered structure offering multispectral detection property was first identified using theoretical calculations based on combined FDTD and Particle Swarm Optimization (PSO) techniques. The crystal structure of the elaborated sensor was analyzed using X-ray diffraction (XRD) method. The device optical properties were investigated by UV–Vis–NIR spectroscopy. The NiO/Ag/ITO heterostructured PD shows a high average absorbance of 63% over a wide spectrum range of [200 nm–1100nm]. Compared with NiO and ITO thin-films, the performances of the heterostructured device are considerably enhanced. It was found that the prepared PD with NiO/Ag/ITO heterostructure merges the benefits of multispectral photodetection with reduced optical losses and efficient transfer of photo-induced carrier. The device demonstrated a high ION/IOFF ratio of 78 dB and an enhanced responsivity under UV, visible and NIR lights (171 mA/W at 365 nm, 67 mA/W at 550 nm and 93 mA/W at 850 nm). The broadband photodetection property enabled by the optimized NiO/Ag/ITO heterostructure opens a new route for the elaboration of low-cost devices that can offer multiple sensing purposes, which are highly suitable for optoelectronic applications.

Self-powered photodetector with improved and broadband multispectral photoresponsivity based on ZnO-ZnS composite

Cost-effective multispectral photodetectors (PDs) exhibiting a high UV-Visible-NIR photoresponse offer an avenue for developing environmental monitoring devices, imaging sensors, object discrimination, and optical links. However, PDs based on a single semiconductor as light-sensitive layer are unable to provide broadband photodetection properties. In this work, a new PD device based on ZnO-ZnS Microstructured Composite (MC) which achieves a high UV-Visible-NIR photoresponse is demonstrated. The ZnO-ZnS MC is elaborated by combining vacuum thermal evaporation technique and a suitable annealing process. Scanning Electron Microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and UV-Vis-NIR spectroscopy were used to elucidate the morphological, structural and optical properties of the prepared sample. It was demonstrated that the ZnO-ZnS MC can be useful to enhance the visible absorbance efficiency by promoting efficient light-scattering effects. It is revealed that the prepared UV-Vis-NIR PD offers a low dark current of 5 nA, a high ION/IOFF ratio of 78 dB and an enhanced responsivity in UV, visible and NIR ranges. The proposed multispectral PD demonstrates a high ION/IOFF current ratio under self-powered working regime. Therefore, the proposed ZnO-ZnS MC is believed to provide new insights in developing efficient, self-powered and low-cost multispectral PDs for high-performance optoelectronic systems.

Laser-Driven Phase Segregation and Tailoring of Compositionally Graded Microstructures in Si–Ge Nanoscale Thin Films

The ability to manipulate the composition of semiconductor alloys on demand and at nanometer-scale resolutions is a powerful tool that could be exploited to tune key properties such as the electronic band gap, mobility, and refractive index. However, existing methods to modify the composition involve altering the stoichiometry by temporal or spatial modulation of the process parameters during material growth, limiting the scalability and flexibility for device fabrication. Here, we report a laser processing method for localized tailoring of the composition in amorphous silicon-germanium (a-SiGe) nanoscale thin films on silicon substrates, postdeposition, by controlling phase segregation through the scan speed of the laser-induced molten zone. Laser-driven phase segregation at speeds adjustable from 0.1 to 100 mm s-1 allows access to previously unexplored solidification dynamics. The steady-state spatial distribution of the alloy constituents can be tuned directly by setting the laser scan speed constant to achieve indefinitely long Si1-xGex microstructures, exhibiting the full range of compositions (0 < x < 1). To illustrate the potential, we demonstrate a photodetection application by exploiting the laser-written polycrystalline SiGe microstripes, showing tunability of the optical absorption edge over a wavelength range of 200 nm. Our method can be applied to pseudobinary alloys of ternary semiconductors, metals, ceramics, and organic crystals, which have phase diagrams similar to those of SiGe alloys. This study opens a route for direct laser writing of novel devices made of alloy microstructures with tunable composition profiles, including graded-index waveguides and metasurfaces, multispectral photodetectors, full-spectrum solar cells, and lateral heterostructures.

In-process monitoring of porosity in additive manufacturing using optical emission spectroscopy

A key challenge in metal additive manufacturing is the prevalence of defects, such as discontinuities within the part (e.g., porosity). The objective of this work is to monitor porosity in Laser Powder Bed Fusion (L-PBF) additive manufacturing of nickel alloy 718 (popularly called Inconel 718) test parts using in-process optical emission spectroscopy. To realize this objective, cylinder-shaped test parts are built under different processing conditions on a commercial L-PBF machine instrumented with an in-situ multispectral photodetector sensor. Optical emission signatures are captured continuously during the build by the multispectral sensor. Following processing, the porosity-level within each layer of a test part is quantified using X-ray Computed Tomography (CT). The graph Fourier transform coefficients are derived layer-by-layer from signatures acquired from the multispectral photodetector sensor. These graph Fourier transform coefficients are subsequently invoked as input features within various machine learning models to predict the percentage porosity-level in each layer with CT data taken as ground truth. This approach is found to predict the porosity on a layer-by-layer basis with an accuracy of ∼90% (F-score) in a computation time less than 0.5 seconds. In comparison, statistical moments, such as mean, variation, etc., are less accurate (F-score ≈ 80%) and require a computation time exceeding 5 seconds.

Integration of multi-layered materials with wide bandgap semiconductors for multi-spectral photodetectors: case for MoS2/GaN and β-In2Se3/GaN

We report on the demonstration of UV/visible and UV/near-IR photodetectors of high spectral responsivity (SR) in a non-conventional heterojunction, realized by combining multi-layered materials with wide band gap Gallium Nitride (GaN). Multi-layer MoS2 and β-In2Se3 flakes were exfoliated separately on epitaxial GaN-on-sapphire, followed by fabrication of photodetectors in a lateral inter-digitated metal semiconductor metal geometry with Ti/Au contacts. Devices exhibited distinct steps in SR graph at 365 nm with responsivity value of 127 A W−1 and at ∼685 nm with responsivity value of 33 A W−1 for MoS2/GaN heterostructure. Whereas, similar steps exhibited at 365 nm with responsivity value of 1.6 A W−1 and at ∼850 nm with responsivity value of 0.03 A W−1 in case of β-In2Se3/GaN heterostructure. The wavelength dependent I–V characteristics showed photo-to-dark current ratio of ∼30 at 685 nm in case of MoS2/GaN heterostructure and ratio of ∼2 at 850 nm for β-In2Se3/GaN heterostructure. The reasons which limit the performance of the devices were also investigated using transient analysis and power dependent responsivity analysis. In summary, current work paves the way for futuristic layered-materials/3D heterostructure devices.