Low Noise Equivalent Power Research Articles

High responsivity zero-biased Mid-IR graphene photodetector based on chalcogenide glass waveguide

Graphene’s unique properties have made it a promising material for high-performance photodetectors due to its interesting features including broadband absorption, fast speed, and strong photothermoelectric effect. Here, an optimized waveguide photodetector incorporating double graphene layers with two cores is presented to boost the responsivity (∼twice), at Mid-IR range. The proposed structure operates in the zero-bias regime to eliminate the dark current issue associated with the zero bandgap nature of graphene and leads to lower noise equivalent power. The presented photodetector operating based on split gates to electrostatically induce the p-n junction in graphene channels, operates based on the photothermoelectric effect and provides responsivity, NEP, and 3 dB bandwidth of 6.3 V/W, 0.34 nW/Hz1/2, and 1.54 GHz, respectively for the detection at λ = 5.2 μm. The feasibility of the proposed structure is proved according to recent experimentally demonstrated photodetectors. Hence, the obtained results are reliable, in practice. The study has been accomplished by numerical simulation of mode profiles and solving the heat equation to extract the characteristics of the proposed photodetector. The zero-power consumption and tunability of the proposed structure make it a promising candidate for sensing, industrial, defense, and environmental monitoring applications with high accuracy.

Graphene Monolayer Nanomesh Structures and Their Applications in Electromagnetic Energy Harvesting for Solving the Matching Conundrum of Rectennas.

In this paper, we investigate various graphene monolayer nanomesh structures (diodes) formed only by nanoholes, with a diameter of just 20 nm and etched from the graphene layer in different shapes (such as rhombus, bow tie, rectangle, trapezoid, and triangle), and their electrical properties targeting electromagnetic energy harvesting applications. In this respect, the main parameters characterizing any nonlinear device for energy harvesting are extracted from tens of measurements performed on a single chip containing the fabricated diodes. The best nano-perforated graphene structure is the triangle nanomesh structure, which exhibits remarkable performance in terms of its characteristic parameters, e.g., a 420 Ω differential resistance for optimal impedance matching to an antenna, a high responsivity greater than 103 V/W, and a low noise equivalent power of 847 pW/√Hz at 0 V.

An Ultrasensitive Bi2O2Se/In2S3 Photodetector with Low Detection Limit and Fast Response toward High-Precision Unmanned Driving.

The machine vision utilized in unmanned driving systems must possess the ability to accurately perceive scenes under low-light illumination conditions. To achieve this, photodetectors with low detection limits and a fast response are essential. Current systems rely on avalanche diodes or lidars, which come with the drawbacks of increased energy consumption and complexity. Here, we present an ultrasensitive photodetector based on a two-dimensional (2D) Bi2O2Se/In2S3 heterostructure, incorporating a homotype unilateral depletion band design. This innovative architecture effectively modulates the transport of both free and photoexcited carriers, suppressing the dark current and facilitating the rapid and efficient separation of photocarriers. Owing to these features, this device exhibits a responsivity of 144 A/W, a specific detectivity of 1.2 × 1014 Jones, and a light on/off ratio of 1.1 × 105. These metrics rank among the top values reported for state-of-the-art 2D devices. Moreover, this device also demonstrates a fast response time of 170/296 μs and a low noise equivalent power of 0.57 fW/Hz1/2, attributes that endow it with ultraweak light imaging capabilities. Furthermore, we have successfully integrated this device into an unmanned driving system, providing a perspective on the design and fabrication of future optoelectronic devices.

Enhanced UV photodetector performance using sputtered Mg-doped ZnO thin film

In this article, we demonstrate UV photodetector synthesized using Mg-doped ZnO thin film (TF) (10 % Mg) grown on a p-Si substrate using the radio frequency (RF) magnetron sputtering system. The fabricated MgZnO TF was annealed at 500 °C in air resulting in notable changes in morphology, optical band gap and crystallinity that significantly improved the UV light sensitivity. The annealed device (MgZnO TF/p-Si) exhibited a remarkable 155-fold increase in photocurrent density compared to the as-deposited device at + 2 V bias. Also, at the same bias the annealed device (500 °C) exhibited high photosensitivity (up to 1262 times), responsivity (20.32 A/W), specific detectivity (1.82 × 1013 Jones) and external quantum efficiency (EQE) (7745 %) in comparison to the as-deposited device. Additionally, the 500 °C device achieved a low noise equivalent power (NEP) of 0.07 × 10−12 W which is about 262 times lower than that of the as-deposited device (18.4 × 10−12 W). Furthermore, on UV illumination (λ = 325 nm) the MgZnO TF/p-Si (500 °C) detector showed fast device response with rise time/fall time values of 0.26 s/0.25 s respectively at + 2 V applied bias.

Investigating UV photodetector capabilities of Pd-functionalized NiO thin films with interdigitated Pt electrodes

In this study, Palladium functionalized NiO thin films (Pd/NiO) were successfully deposited using a sputtering technique for the photodetector application. FESEM and EDX analysis were performed to confirm the morphology and the presence of constituent elements in the Pd/NiO films. The defect states and surface chemistry were analyzed using XPS, and PL measurements. The Pd/NiO thin film exhibited excellent responsivity (∼ 62 mA/W) and detectivity (∼ 31.7 × 106 Jones) at a low power density of 200 µW/cm2 in the UV range (∼ 355 nm). Additionally, the low Noise Equivalent Power (NEP) of ∼ 1.78 × 10-9 WHz−1/2 at 200 μW indicates the Pd/NiO photodetector capability to effectively detect light signals even at low optical power for various applications.

Revealing the photo-sensing capabilities of a super-flexible, paper-based wearable a-Ga2O3 self-driven ultra-high-performance solar-blind photodetector

To address the growing demand for wearable optoelectronic devices in secure communication, environmental monitoring, biomedical, and military applications, the development of self-driven solar-blind photodetectors (SBPDs) is crucial. This work reports the fabrication of super-flexible, wearable, and ultralight self-driven SBPD based on an amorphous-Ga2O3 film grown on various paper substrates (including glossy, parchment, and 75 GSM paper) with interdigitated Pt electrodes using a magnetron sputtering. The developed device on glossy, parchment, and 75 GSM paper exhibits superior responsivity of 8.30 mAW−1, 14.53 mAW−1, and 20.96 mAW−1, along with a fast response speed of 115/118 ms, 90/95 ms, and 65/67 ms for 266 nm light irradiation under self-driven conditions. Comparatively superior performance is recorded for 75 GSM paper-based device, owing to their surface roughness, porosity, and microfibrous structure, which enhance light absorption in the device. In addition, the developed device shows an ultraviolet C-to-visible rejection ratio of over ∼ 106, a high specific detectivity of 2.01 × 1011 Jones, a high responsivity of 1.38 × 103 mAW−1 and a low noise equivalent power of 2.44 × 10-13 WHz−1/2 at a 5 V bias on 75 GSM paper. The photocurrent remains close to its initial values even when bent to lo/l = 5, demonstrating outstanding flexibility, bending endurance, and deformability. The performance of the self-driven PD remains stable over two months and steady up to 600 bending cycles. Further, the fabricated device underwent thorough testing across various wearable applications, and the analysis demonstrates discernible alteration in its performance across real-world scenarios. This technique paves the way for developing self-driven paper-based SBPDs with high-performance, wearable, next-generation flexible optoelectronic device applications.

Multi-Gb/s free-space laser communication at 4.6-μm wavelength using a high-speed, room-temperature, resonant-cavity infrared detector (RCID) and a quantum-cascade laser

Research has shown that free-space laser communication systems may experience fewer outages due to atmospheric impairments such as haze, fog, clouds, and turbulence by operating at a longer wavelength in the mid-wave or long-wave infrared, if disadvantages such as lower-performance transceiver components may be overcome. Here we report a resonant cavity infrared detector (RCID) with 4.6-µm resonance wavelength that enables 20-dB larger link budget than has been reported previously for ∼ 5 Gb/s operation. The device combines high responsivity, 1.97 A/W, with a low noise equivalent power (NEP) of 0.7 pW/Hz at room temperature, and a high bandwidth of 6.7 GHz at 3-dB. The relatively large surface-normal-incidence device with 30-µm diameter simplifies the coupling relative to intra-subband quantum cascade detectors. Although the RCID NEP is expected to increase with frequency to ∼ 1.5 pW/Hz, we estimate that the total equivalent noise power in a 2.5-GHz bandwidth is less than 200 nW. When combined with a relatively high power (∼100-mW) distributed-feedback quantum cascade laser, the difference of > 50 dB between modulated laser power and RCID noise significantly outpaces that of existing devices.

E-beam synthesized fast-switching TiO2/SnO2 type-II heterostructure photodetector

A fast-switching TiO2/SnO2 heterostructure thin-film (TF) photodetector synthesized by electron beam evaporation technique is analyzed in this study. The substrate utilized is n-type silicon (Si), while gold (Au) is employed as the top electrode. To assess sample morphology and confirm elemental composition, field emission scanning electron microscopy (FESEM), energy dispersive x-ray spectroscopy (EDS), and chemical mapping were conducted. Structural characteristics were determined using X-ray diffraction (XRD) analysis. The XRD analysis confirmed the presence of various phases of TiO2 (anatase and rutile) and SnO2 (rutile). UV-Vis spectroscopy revealed multiple absorption peaks, at 447 nm, 495 nm, 560 nm, and 673 nm, within the visible spectrum. The device demonstrates high detectivity (D∗) of 1.737×109 Jones and a low noise equivalent power (NEP) of 0.765×10−10W. Evaluation of the device’s switching response through current-time characteristic (I-T) analysis indicates rapid switching with a rise time and fall time of 0.33 s and 0.36 s, respectively.

Improving ZnO ultraviolet Schottky photodetectors by inserting a MoS2 layer

ZnO Schottky junction photodetectors (PDs) has become a research focus due to their wide application, high-performance and low-cost. However, their development has been limited by the low photo-response. Two-dimensional MoS2 exhibit numerous advantages, including a tunable band gap, a strong exciton effect, and broadband absorption. In this work, we incorporate MoS2 into ZnO thin films using a simple spin-coating method to create Schottky ultraviolet (UV) PDs that show a remarkably increased responsivity (by 885%) and a substantially improved photo-current (by one order of magnitude). Furthermore, they exhibit a relatively low noise equivalent power (5.11×10−13 W) and a high normalized detectivity 2.96×1011 Jones. This outstanding performance can be attributed to the enhanced absorption and efficient charge transfer of ZnO film after introduction of MoS2 layer. In this study, an easy method is presented for creating high-performance ZnO Schottky PDs.

Topological insulator MnBi2Te4 and its van der Waals heterostructure for sensitive room-temperature terahertz photodetection

Dirac fermions are a distinctive feature of topological insulators (TIs) due to the existence of topologically protected surface states, making TIs a promising choice for long-wavelength photodetection. However, TIs-based photodetection often suffers from significant dark current. This paper demonstrates broadband detection through the direct generation of photocarriers in metal-MnBi2Te4 (MBT) -metal structures at room temperature. By integrating MBT and Bi2Te3 into van der Waals structures, the heterostructure device can reduce dark current and have excellent sensitivity at room temperature. Especially, MBT/Bi2Te3 photodetectors have a fast response time (<1 μs) and low noise equivalent power <0.5 nW Hz−1/2 at self-powered mode due to photothermoelectric conversion. The MBT/Bi2Te3 photodetector detects low-energy photons through the hybrid integration of new low-dimensional materials that will be already suitable for imaging applications, further emphasizing the unique advantages of TIs in the field of terahertz technology.

Enhancing detectivity of organic photodetectors through the biomass carbon quantum dots from sugarcane bagasse

In recent years, organic photodetectors (OPDs) have received sustained attention due to their tunable wavelength detection, low-cost manufacturing and compatibility with flexible devices. However, as the preparation process proceeds, organic materials inevitably produce some toxic by-products, which triggers an urgent need for green non-toxic optical materials. This paper reports a carbon quantum dot (CQDs) extracted from the green precursor sugarcane bagasse as the sole carbon source, and successfully applied in the OPDs with a structure of FTO/ZnO:CQDs/P3HT/MoO3/Ag for the first time. After CQDs incorporation, the surface of the ZnO thin films exhibits an increased density of oxygen vacancies and adsorbed oxygen. The resulting OPDs exhibit a high detectivity of 2.46 × 1011 Jones and a low noise equivalent power of 1.15 × 10−12 W @ 525 nm. The facile preparation method of CQDs offers a promising opportunity for the green and sustainable synthesis of advanced functional nanomaterials, and the successful demonstration paves new way for the advancement of high-performance OPDs.

Negative Photoconductivity of Fe3GeTe2 Crystal with Native Heterostructure for Ultraviolet to Terahertz Ultra-Broadband Photodetection.

Gaining insight into the photoelectric behavior of ferromagnetic materials is significant for comprehensively grasping their intrinsic properties and broadening future application fields. Here, through a specially designed Fe3GeTe2/O-Fe3GeTe2 heterostructure, first, the broad-spectrum negative photoconductivity phenomenon of ferromagnetic nodal line semimetal Fe3GeTe2 is reported that covers UV-vis-infrared-terahertz bands (355nm to 3000µm), promising to compensate for the inadequacies of traditional optoelectronic devices. The significant suppression of photoexcitation conductivity is revealed to arise from the semimetal/oxidation (sMO) interface-assisted dual-response mechanism, in which the electron excitation origins from the semiconductor photoconductivity effect in high-energy photon region, and semimetal topological band-transition in low-energy photon region. High responsivities ranging from 103 to 100mA W-1 are acquired within ultraviolet-terahertz bands under ±0.1V bias voltage at room temperature. Notably, the responsivity of 2.572 A W-1 at 3000µm (0.1 THz) and the low noise equivalent power of 26 pW Hz-1/2 surpass most state-of-the-art mainstream terahertz detectors. This research provides a new perspective for revealing the photoelectric conversion properties of Fe3GeTe2 crystal and paves the way for the development of spin-optoelectronic devices.

Enhancing Self‐Powered Terahertz Photodetection with VSe2 and Van Der Waals Heterostructure Integration via Photothermoelectric Effect

AbstractOwning unique optical and electronic properties, two dimensional (2D) materials have made remarkable strides in the field of photodetection applications. However, achieving highly sensitive and ultra‐broadband detection from microwave to terahertz (THz) range (0.02–0.54 THz) remains a significant challenge for photodetectors. This study presents a self‐powered THz photodetector based on VSe2 and its van der Waals heterostructure. The photoresponse of the photodetector is primarily attributed to the photothermoelectric effect. At room temperature, the device exhibits lower noise equivalent power values of 21 pW Hz−1/2 at 0.28 THz. This work has achieved ultra‐broadband detection and demonstrated the potential for large‐area imaging, providing a new avenue for the application of THz technology in nondestructive testing and biometric identification fields.

An Extremely Low Noise-Equivalent Power Photoreceiver Using High-Gain InGaAs/AlGaAsSb APDs

An Extremely Low Noise-Equivalent Power Photoreceiver Using High-Gain InGaAs/AlGaAsSb APDs

Terahertz bow-tie diode based on asymmetrically shaped AlGaN/GaN heterostructures

Asymmetrical shaping of AlGaN/GaN heterostructures containing a conductive layer of two-dimensional electron gas (2DEG) was used for the development of bow-tie (BT) diodes for room temperature terahertz (THz) detection. Considering operation of the THz BT diode in the unbiased mode as preferable for practical applications, we investigated the diodes with an obvious asymmetry of IV characteristics, which was found to be more pronounced with the decrease of an apex width, resulting in the sensitive THz detection. A nonuniform heating of carriers in a metalized leaf of the BT diode was attributed as the main mechanism that caused the rectification of THz waves. The responsivity and noise-equivalent power (NEP) at the fundamental antenna frequency of 150 GHz were up to 4 V/W and 2 nW/√Hz, respectively. Such high sensitivity of BT diodes allowed us to measure for the first time the response spectrum of the asymmetric BT antenna demonstrating fundamental and higher order resonances in good agreement with finite-difference time-domain simulation data in a broad spectrum range. The detailed investigation of the lowand high-frequency noise characteristics of AlGaN/GaN BT diodes revealed that only thermal noise needs to be considered for the unbiased operation, the value of which was relatively low due to a high density of 2DEG enabling low resistivity values. Moreover, we observed that the responsivity of BT diode scales with its resistance, revealing that tapering of the diode apex below a few microns could be ineffective in applications which require low NEP values.

Selective Growth of Type‐II Weyl‐Semimetal and Van der Waals Stacking for Sensitive Terahertz Photodetection

AbstractThe emergence of novel topological semimetal materials, accompanied by exotic non‐equilibrium properties, not only provides a fertile playground for a fundamental level of interest but also opens exciting opportunities for inventing new applications by making use of different light‐induced effects such as nonlinear optics, optoelectronics, especially for the highly pursued terahertz (THz) technology due to the gapless electronic structures. Exploring type‐II Weyl semimetal endowed with the richness of quantum wavefunction and peculiar band structure, underlie strong nonlinear coupling with THz waves. Here, the selective growth of type‐II Weyl semimetal NbIrTe4 by means of a self‐flux approach is reported, which hosts strongly tilted Weyl cones and exotic Fermi arcs. The oscillating THz field induced by the antenna is engineered in terms of planar metal‐topological semimetal‐metal structure, along with van der Waals stacking, which allows for self‐powered photodetection at room temperature. The results elucidate the superior performance of NbIrTe4‐graphene heterostructure‐based photodetectors with responsivity up to 264.6 V W−1 at 0.30 THz, fast response of 1 µs as well as low noise equivalent power ˂0.28 nW Hz−0.5 is achieved, already exhibiting high‐quality imaging at THz frequency. The results promise superb impacts in exploring topological Weyl semimetals for efficient low‐energy photon harvesting.

Enhancement of terahertz response in a microstructure-integrated-type-II Dirac semimetal

Terahertz detection technology has been confronted with formidable impediments, notably the paucity of sensitivity and operating temperature for photodetectors based on traditional bulk materials. In an attempt to surmount the difficulties, we propose an innovative terahertz detector based on a PtSe2 (type-II Dirac semimetallic material) integrated asymmetric antenna structure that can enhance the terahertz photoresponse by capitalizing on meticulous fabrication procedures. Experimental outcomes demonstrate the remarkable characteristics of the photodetector in the terahertz band, encompassing fast response time (7 µs), large responsivity (3.267 A/W), and low noise equivalent power (3.96 pW/Hz0.5). These accomplishments can be ascribed to the incorporation of the asymmetric metal contact of the four-leaf clover antenna structure and the excellent thermoelectric characteristics of PtSe2. This pioneering investigation consequently unveils a novel methodology for the creation of proficient PtSe2-based terahertz detectors and serves as a catalyst for the promotion of applications and further research within the terahertz sphere.

Self-driven high-performance broadband photodetector based on WSe2 nano-speckles

Long-term exposure to visible or infrared light may have harmful biological consequences, such as erythema, that can damage the cornea and retina. Additionally, trapped infrared light contributes to climate change on a global scale. Self-driven broadband photodetectors, which do not need an auxiliary battery and function in a multiband region of the electromagnetic spectrum, can be the solution to monitor such radiation. Though two-dimensional (2D) materials offer excellent optoelectronic characteristics, these materials still need to be fully explored to fabricate high-performance self-driven broadband photodetector. The study proposes nano-speckles like WSe2-based self-driven photodetection that operate in a broad spectral range from vis to NIR. The developed device exhibits 2.1 mAW−1 high responsivity at 860 nm illumination at zero bias (self-driven mode). Also, at zero bias a responsivity of 1.09 mAW−1 for 532 nm light illumination and 1.05 mAW−1 for 625 nm light illumination was obtained. Further, the device shows ultra-high responsivity of 1.2 × 104 mAW−1 and a very high external quantum efficiency of 2.84 × 103% with low noise equivalent power 3.27 × 10−13 WHz−1/2 at 860 nm light illumination under photoconductive mode. This report provides a promising simple synthesis method for fabricating a self-driven photodetection device that covers vis to NIR range with high sensitivity for future optoelectronic applications.

Deep ultraviolet–visible highly responsivity self-powered photodetector based on β-Ga2O3/GaN heterostructure

We have reported unique β-Ga2O3 nanoscale-strips (β-Ga2O3-NSS) morphology on epitaxial Gallium nitride film by thermal oxidation and fabricated heterostructure based self-powered photodetector (PD) operable from 230 nm to 800 nm (UVC to Vis) broad spectral range. The device demonstrates an ultrahigh responsivity of 5.8 × 103 mAW−1 under 266 nm illuminations at zero bias. The developed broadband photodetector at zero applied bias exhibits excellent responsivity of 2600, 56, and 450 mAW−1 under light illuminations of 355 nm, 455 nm, and 532 nm, respectively. In addition, the device also shows very high responsivity (1.6 × 105 mAW−1) with low noise equivalent power (10−13 WHz−1/2) and excellent external quantum efficiency (104%) under the bias of 5 V at 266 nm. The outstanding performance of the developed device is attributed to the light-trapping geometry of the β-Ga2O3-nanoscale-strips. The simple architecture of the device opens up new avenues for the fabrication of the next generation of Ga2O3-based broadband photodetection devices.

High‐Sensitive and Fast Speed UV Photodetector Based on HfSe2/InSe Heterostructure

AbstractThe type‐II band‐aligned van der Waals (vdW) heterostructures are favorable for photocarrier separation and are often used for designing high‐performance photodetectors. Inspired by this, a metal‐mirror electrode enhanced HfSe2‐InSe vdW heterostructure photodetector is designed and demonstrated excitement performance in UV light detection. It is demonstrated the moderate bandgap heterostructure can be configured as a high‐performance UV photodetector with excellent light on/off ratio of 106, high photoresponsivity of 47.3 AW−1, competitive high specific detectivity of 3.2 × 1012 cmHz1/2W−1 and very low noise equivalent power of 2.8 × 10−16 WHz−1/2. Notably, the photoresponse speed of the device is very fast, with a rise time of 4.1 µs and a decay time of 5.4 µs. The results indicate that 2D HfSe2‐InSe vdW heterostructure possesses great potential applications in UV photodetection.