Heterojunction Photodiodes Research Articles

Robust Light Detection from Ultraviolet to Near‐Infrared with ZnGa2O4/p‐Si Heterojunction Photodiode and Its Application for Optoelectronic Physically Unclonable Functions

AbstractThe Si‐based self‐powered broadband photodiode (SSBP) is prized for its ability to swiftly detect light across a wide spectrum without requiring an external voltage. However, boosting its efficiency remains challenging due to its high refractive index and limited UV light penetration. A combination of Si with ZnGa2O4, an ultra‐wide‐bandgap spinel material, can bring new opportunities to address these shortcomings of SSBP. In this study, a ZnGa2O4/p‐Si heterojunction photodiode is presented, which is capable of detecting UV to near‐infrared light autonomously. Operating without bias, this device exhibits excellent rectification and detects wavelengths from 265 to 1000 nm, achieving impressive performance metrics such as a photo‐to‐dark current ratio of 5.8 × 104, response speed of less than 3 ms, responsivity of 117 mA W−1, and specific detectivity of 5.5 × 1012 Jones while the photodiode demonstrates exceptional stability and durability under harsh conditions. The versatility of this device is demonstrated by applying it to the optical imaging sensors and physically unclonable security devices. This study provides new inspirations for the development of the energy‐efficient and emerging optical sensing technologies.

Optimizing optoelectronics performance: theoretical and experimental study on ZnO thin film for Al/ZnO/p-Si photodiode

Abstract In this paper, a ZnO photodiode in a p-n heterojunction configuration is fabricated on a p-type Si substrate focusing specifically on ZnO/p-Si heterojunction photosensitive devices and photodiodes (PDs) using Al contacts. Through an experimental and theoretical analysis approach aims to evaluate the effects of important parameters, including ZnO layer thickness, defect density, and contact materials, on PD’s efficiency. Numerical analysis simulations comparatively examine the experimentally fabricated device performance at a 5 nm ZnO layer thickness by balancing photon absorption and carrier formation while minimizing carrier transport limitations. Experimentally process, an Atomic Layer Deposition (ALD) system was used to grow ZnO interlayers on one side of the polished Si wafer. Then, Al metallic contacts were created on the ZnO layers using a hole array mask. The PDs were then subjected to electrical characterization using I-V and I-t measurements under various illumination densities. Al/ZnO/p-Si PD’s device with active performance has been produced and analyzed with electrical parameters such as barrier height, photocurrent, spectral response, ideality factor and EQE were derived, analyzed and studied. In conclusion, this work provides a comprehensive understanding of the performance of Al/ZnO/p-Si PD at varying illumination intensities and offering a detailed analysis of key parameters influencing device efficiency for future optoelectronics applications.

TexSe1-x Shortwave Infrared Photodiode Arrays with Monolithic Integration.

TexSe1-x shortwave infrared (SWIR) photodetectors show promise for monolithic integration with readout integrated circuits (ROIC), making it a potential alternative to conventional expensive SWIR photodetectors. However, challenges such as a high dark current density and insufficient detection performance hinder their application in large-scale monolithic integration. Herein, we develop a ZnO/TexSe1-x heterojunction photodiode and synergistically address the interfacial elemental diffusion and dangling bonds via inserting a well-selected 0.3 nm amorphous TeO2 interfacial layer. The optimized device achieves a reduced dark current density of -3.5 × 10-5 A cm-2 at -10 mV, a broad response from 300 to 1700 nm, a room-temperature detectivity exceeding 2.03 × 1011 Jones, and a 3 dB bandwidth of 173 kHz. Furthermore, for the first time, we monolithically integrate the TexSe1-x photodiodes on ROIC (64 × 64 pixels) with the largest-scale array among all TexSe1-x-based detectors. Finally, we demonstrate its applications in transmission imaging and substance identification.

The n-MoO3/p-Si heterojunction photodiode: Influence of the MoO3 film thickness on the ultraviolet and infrared photodetector performance

Here, we studied the effect of the MoO3 thin film thickness on the ultraviolet (UV) and infrared (IR) photodiode properties of the n-MoO3/p-Si heterojunction structure. Initially, the metal molybdenum (Mo) thin films with different thicknesses (50,150, and 250 nm) were created via DC magnetron sputtering on a p-type Si substrate. Then, the MoO3 thin films were synthesized using a thermal oxidation method with an optimal oxygen flow rate of 60sccm. XRD and Raman analysis showed that the structure of prepared thin films has converted from an amorphous to an orthorhombic (α-MoO3) crystalline phase with increasing thickness. The optical transmittance of the layers was tuned by controlling the thickness, and the maximum transmittance for the 50 nm-thick film was achieved in the broad wavelength range of 300–1100 nm. The current density–voltage (J–V) characteristics indicate the prepared samples' rectifying behavior under dark conditions. The heterojunction photodiode with a 50 nm-thick MoO3 layer shows the best performance. This sample had a maximum amount of transmittance in the UV–visible and IR regions, compared to other samples, which leads to efficient electron-hole separation and transportation. This sample demonstrates a significant photoresponse ratio (ILight/IDark) of about 55 and 52.5 in the ultraviolet (UV) and infrared (IR) regions, respectively.

2D Gr/WSe2/MoTe2 vertical heterojunction for self-powered photodiode with ultrafast response and high sensitivity

Two-dimensional materials without lattice constraints can be combined into form heterojunctions via van der Waals forces, providing opportunities for the future development of novel high-performance photodetectors. In non-vertical heterojunction devices with long carrier transport channels, SRH recombination due to defect and interface states in the heterojunction and Langevin recombination due to Coulomb interactions induce large amounts of photogenerated carrier recombination, leading to low quantum efficiencies of the heterojunction. At the same time, defect and interface trap states, as well as the long channel of the non-vertical heterojunction device, lead to a slow response speed of the device. In this work, a 2D WSe2/MoTe2 vertical heterojunction photodiode with a transparent graphene top electrode has been designed to simultaneously achieve high sensitivity and fast response speed of photodetectors. Benefiting from the vertical device structure, high-quality interface and low contact resistance, the photogenerated electron-hole pairs can be efficiently separated and transported. The photodiode exhibits remarkable rectification characteristics with a rectification ratio as high as 1.4 × 104, and provides a broadband and self-powered photodetection from the visible to NIR bands (405–1064 nm) with a maximum responsivity of 0.33 A/W at 785 nm. In particular, the photodiode achieves an ultra-fast rise/fall time of 6.49/6.22 μs at 0 V and a further reduction of the response time to 1.68/1.2 μs at a reverse bias of −1 V. This ultra-fast response allows the photodiode to detect switching signals with a cutoff frequency of more than 70 kHz and 200 kHz at 0 V and −1 V, respectively. This work opens up new opportunities for the development of integrated 2D photodetectors with low power consumption, high sensitivity, and high speed.

Tin Lodide Thin Films Growth via Plasma Enhanced Chemical Vapor Deposition and its Optimization Using V–I Probe Impedance Analyser for Optoelectronic Applications

AbstractTin(ii) iodide (SnI2) faces significant challenges in photodetector applications, primarily due to its sensitivity to moisture and degradation over time. Achieving uniform, high‐quality films with low impurity and defect levels is also a challenge. Potential solutions include advanced deposition techniques to improve film quality and stability, surface passivation and encapsulation, doping and alloying. In this study, SnI2 thin films have been deposited for the first time using plasma enhanced chemical vapour deposition (PECVD) technique to the best of our knowledge. Process parameters like deposition pressure and RF‐power have been optimised via non‐intrusive in‐situ V−I probe impedance analyser. SnI2 thin films have been deposited on glass & transparent conducting oxide (TCO) and p‐Si wafer at various RF‐power to make SnI2/p‐Si heterojunction followed by metallization to make Ag/SnI2/p‐Si/Ag heterojunction photodetector. Characterization techniques like thin film thickness measurement, UV‐Vis‐NIR spectroscopy, Photoluminescence spectroscopy, glancing incidence x‐ray diffraction (GIXRD), SEM and I−V measurements were carried out to study its optical, structural and electronic properties. Fabricated devices, Ag/SnI2/p‐Si/Ag heterojunction photodiode exhibits best critical performance for the film deposited at 150 W having rectifying ratio of 6.9×104 at 1.0 V and photo‐sensitivity of 1.6×104 at 100 mW/cm2 light intensity.

Ultrahigh-performance heterojunction bipolar phototransistor enabled by bilateral piezoelectric charge modulation effect

Heterojunction photodiodes based on p-n junction with enhanced piezo-phototronic effect have been extensively studied. However, the photoresponsivity of conventional photodiodes is small due to the natural zero current gain. Heterojunction phototransistor usually has greater photoresponsivity due to the non-zero current gain. More importantly, heterojunction phototransistor owns two interfaces, offering the opportunity to introduce the bilateral piezoelectric charge modulation effect for further performance enhancement compared to the conventional single-interface piezo-phototronic effect in photodiode. In this work, a base-floating heterojunction bipolar phototransistor (FHPT) based on n-ZnO/p-Si/n-ZnO structure with a spectral detection range from ultraviolet (UV)–visible is demonstrated. The positive piezoelectric charge generated at the two interfaces of the collector junction and the emitter junction, combined with the optimal base width and low resistance base doping concentration of the FHPT, leads to an excellent photoresponsivity (18046 A/W, 365 nm), high detectivity (5.7×1012 Jones), and a wider modulation (7120 %). The physical mechanism leading to the ultrahigh performance is attributed to the cooperative positive piezoelectric charge at the two interfaces, simultaneously reducing the effective base width and lowering the emitter junction barrier. This work illustrates the regulation of heterojunction phototransistor performance by the bilateral piezoelectric charge modulation effect, providing insightful guidance to high-performance phototransistor design.

Enhanced SWIR Light Detection in Organic Semiconductor Photodetectors through Up-Conversion of Mid-Gap Trap States.

Shortwave-infrared (SWIR) photodetectors are vital for many scientific and industrial applications including surveillance, quality control and inspection. In recent decades, photodetectors based on organic semiconductors have emerged, demonstrating potential to add real value to broadband and narrowband imaging and sensing scenarios, where factors such as thermal budget sensitivity, large area aperture necessity, cost considerations, and lightweight and conformal flexibility demands are prioritized. It is now recognized that the performance of organic photodetectors (OPDs), notably their specific detectivity, is ultimately limited by trap states, universally present in disordered semiconductors. This work adopts an approach of utilizing these mid-gap states to specifically create a SWIR photo-response. To this end, this work introduces a somewhat counter-intuitive approach of "trap-doping" in bulk heterojunction (BHJs) photodiodes, where small quantities of a guest organic molecule are intentionally incorporated into a semiconducting donor:acceptor host system. Following this approach, this work demonstrates a proof-of-concept for a visible-to-SWIR broadband OPD, approaching (and, to some extent, even exceeding) state-of-the-art performance across critical photodetector metrics. The trap-doping approach is, even though only a proof-of-concept currently, broadly applicable to various spectral windows. It represents a new modality for engineering photodetection using the unconventional strategy of turning a limitation into a feature.

Non-volatile 2D MoS2/black phosphorus heterojunction photodiodes in the near- to mid-infrared region

Cutting-edge mid-wavelength infrared (MWIR) sensing technologies leverage infrared photodetectors, memory units, and computing units to enhance machine vision. Real-time processing and decision-making challenges emerge with the increasing number of intelligent pixels. However, current operations are limited to in-sensor computing capabilities for near-infrared technology, and high-performance MWIR detectors for multi-state switching functions are lacking. Here, we demonstrate a non-volatile MoS2/black phosphorus (BP) heterojunction MWIR photovoltaic detector featuring a semi-floating gate structure design, integrating near- to mid-infrared photodetection, memory and computing (PMC) functionalities. The PMC device exhibits the property of being able to store a stable responsivity, which varies linearly with the stored conductance state. Significantly, device weights (stable responsivity) can be programmed with power consumption as low as 1.8 fJ, and the blackbody peak responsivity can reach 1.68 A/W for the MWIR band. In the simulation of Faster Region with convolution neural network (CNN) based on the FLIR dataset, the PMC hardware responsivity weights can reach 89% mean Average Precision index of the feature extraction network software weights. This MWIR photovoltaic detector, with its versatile functionalities, holds significant promise for applications in advanced infrared object detection and recognition systems.

Lead-free methyl ammonium tin iodide perovskite thin film growth in single step via plasma enhanced chemical vapour deposition technique and its optoelectronic properties

In the present work, lead free methyl ammonium tin iodide (CH3NH3SnI3 or MASnI3) perovskite thin films have been deposited via single step plasma enhanced chemical vapour deposition (PECVD) technique. In our earlier work, we reported lead based methyl ammonium lead iodide (CH3NH3PbI3 or MAPbI3) perovskite thin film deposition in 2-step, using sputtering technique for the PbI2 thin films and PECVD technique for CH3NH3I (MAI) thin films. Similarly, CH3NH3SnI3 perovskite thin films are deposited in this work using PECVD technique in single step. Lead is substituted with tin due to its toxic behaviour, environmental and health related issues. CH3NH3SnI3 perovskite is doped n-type via changing the molar ratio of SnI2 and CH3NH3I. SnI2/CH3NH3I ratio is changed from 0.33 to 2 to study the n-type doping of CH3NH3SnI3 perovskite. Deposited CH3NH3SnI3 perovskite thin films are deposited over p-type silicon wafer to make n-type doped n-CH3NH3SnI3/p-Si heterojunction photodiode.

On the piezo-phototronic effect in heterojunction photodiode with type-II energy band: Simulation on complex incident light illumination

A photodiode, a semiconductor device, is designed to convert light into an electric current. The piezo-phototronic effect, arising from the interplay of semiconductor properties, piezoelectric polarizations, and photo-excitations, presents a promising avenue for enhancing photodiode performance. This research is dedicated to analyzing the impact of the piezo-phototronic effects on p-Si/n-ZnO heterojunction photodiodes when subjected to 365 nm illumination, a situation more intricate than the commonly studied 648 nm illumination. Employing numerical simulation methods, we systematically investigated the influence of varying ZnO and Si lengths on the piezo-phototronic effect, with a focus on the depletion region and neutral region current perspectives. Our findings reveal that adjusting these lengths can heighten sensitivity at low currents or lead to increased base currents. Additionally, the study delves into the effects of doping concentration, minority carrier lifetime, and mobility on device characteristics. This investigation contributes essential insights for a comprehensive understanding of piezo-phototronic effects and establishes a foundational framework for the design of industrial devices.

A High‐Speed Image Sensor Based on Large‐Area MoTe2/Si Photodiode Arrays

AbstractThe market demand for optoelectronic devices is increasing, leading to a need for low‐cost, high‐performance image sensors that can operate effectively in challenging environments such as darkness and fog. The emerging 2D transition metal dichalcogenides (TMDs) have garnered significant interest due to their exceptional optoelectronic properties and compatibility with silicon (Si) complementary metal oxide semiconductor (CMOS) technology. However, the large‐scale synthesis of TMD films and uniform preparation of photodiode arrays remain challenging. This paper reports a synthesis method for heteroepitaxial growth of 2H‐ molybdeum diyelluride (MoTe2) semiconducting films on 3D wafer‐level Si substrates. Using this method, arrays of 2H‐MoTe2/Si heterojunction photodiodes are prepared that demonstrate excellent uniformity and 100% device yield. The photodiodes exhibit satisfactory optoelectronic properties, including a small dark current maintained within a range of 1–3 nA and a maximum responsivity of 521.1 mAW−1 under near‐infrared light at 800 nm, with rise and fall times of less than 4 ms. To demonstrate the image‐sensing capabilities of the photodiode array under visible and near‐infrared (NIR) light illumination, a complete imaging system is designed.The MoTe2/Si photodiode arrays examined in this study offer a practical solution for integrating Si‐based readout circuits and photodetector arrays on a single chip.

Organic Visible‐Blind Ultraviolet Photodiodes and Pixel‐Array Imagers Based on [1]Benzothieno[3,2‐b]Benzothiophene (BTBT) Derivatives

AbstractVisible‐blind ultraviolet (VBUV) photodetectors are designed for UV detection without responding to visible light, thus having many applications in communications, flame detection, environment monitoring, and astronomy. Herein, an organic device concept based on the bulk heterojunction (BHJ) photodiode is presented for high‐performance VBUV photodetection and imaging. The BHJ, comprised of an organic electron donor, 2,7‐dioctyl[1]benzothieno[3,2‐b][1]benzothiophene (C8‐BTBT), and an electron acceptor, indene‐C60 bisadduct (ICBA), shows efficient generation and transport of free charges upon UV irradiation. The organic photodiode (OPD) delivers exceptional VBUV photodetection performance. At a low voltage of −0.5 V, the device exhibits a wide linear dynamic range of 98.15 dB. Furthermore, the OPD can detect ultra‐low light intensities down to 0.58 µW cm−2 with a high photoresponsivity of 0.12 A W−1 and specific detectivity of 2.75 × 1012 Jones. More importantly, by integrating the OPD with a readout integrated circuit, the pixel‐array organic VBUV imager is demonstrated to have high‐quality imaging capability. The results reveal a novel strategy to design VBUV photodetectors and imagers with balanced performance, cost, area, flexibility, and power consumption.

High gain NiO/ZnO heterojunction photodiodes operated in Deep-ultraviolet region

Epitaxially matched (0001) Al2O3 single substrates are utilized to design p-n heterojunctions (p-NiO/n-ZnO) as they offer low defect density for device fabrication due to small lattice mismatches. Using the radio frequency sputtering technique, the NiO/ZnO thin film-based heterojunction has been fabricated by varying the n-type film's (ZnO) thickness for ultra-violet (UV) photodiode application. It has been investigated how different ZnO film thicknesses affect junction parameters and photoresponse properties. The high photosensitivity (∼ 104), enhanced current gain (∼ 105) and fast response obtained at very low UV intensity (0.62μW/cm2) at 300 nm wavelength are attributed to the internal gain mechanism (recombination tunnelling and space-charge limited current conduction with the remarkable effect of the presence of excess free oxygen) in these devices. The prepared heterojunction photodiode with high speed and deep-UV sensitivity can be a potential solution for visible blind UV detection.

Narrow-band n-GaN/n-Si isotype heterojunction photodiode: A simplified approach for photodiode development

An innovative approach has been explored to fabricate a high-performance photodiode in semiconductor device production, utilizing the thermal evaporation technique to grow GaN thin films. Structural analyzes were conducted on both as-deposited and annealed samples, and their properties were determined using various characterization techniques, including FESEM, XRD, XPS, Hall effect, photoluminescence, and UV-Vis spectrophotometer measurements. Valuable information has been gained about the potential of this alternative approach for fabricating GaN-based electronic devices. In this study, Al/n+-GaN/n-Si/Ag (as-deposited GaN) and Al/n-GaN/n-Si/Ag (annealed GaN) structures have been fabricated. It was found that the device produced from the as-deposited GaN thin film exhibited better performance than the annealed one. The isotype heterojunction n+-GaN/n-Si photodiode exhibited exceptional performance in detecting NIR light at a wavelength of 1050 nm under a 0 V bias. It has a full-width at half-maximum (FWHM) value of 120 nm and achieved a photoresponsivity value of 355 mA/W at a light output of 10 mW/cm². It is further supported by its external quantum efficiency of 42% and detectivity value of 6.93×1011 Jones at the peak wavelength and very fast response speed with ∼33 µs rise/fall times. These findings highlight the potential of photodiode as an efficient narrow-band in the NIR region.

Analysis of photodiode and barrier properties of CoPc/n-Ge heterojunction under various illumination wavelengths

The present investigation reports the analysis of barrier parameters of the CoPc/n-Ge heterojunction photodiode under varied illumination wavelengths from 500 nm to 1200 nm in steps of 25 nm. The efficiency of this photodiode was also summarized using responsivity, detectivity and quantum efficiency for different illumination wavelengths. The photocurrent seems to be maximum for 850 nm and 1175 nm and shows higher responsivity of 1.72 A/W and 2.38 A/W at 775 nm and 1125 nm wavelength respectively. The quantum efficiency of the photodiode was found to be 275 % at illumination wavelength of 775 nm and 263 % at 1125 nm. For the selective illumination wavelengths (775 nm, 850 nm, 1125 nm and 1175 nm), the electrical properties of the CoPc/n-Ge photodiode were studied. Noticeable variation in the barrier parameters of the photodiode is observed with illumination than compared to dark. Significantly, the series resistance was found to be decreased and shunt resistance is increased with illumination wavelength than compared to dark. Current conduction mechanisms were also investigated in both the forward and reverse bias of the photodiode. The forward current transport processes show that at moderately high bias the current conduction might be associated with TCLC. It is also evidenced from the reverse conduction mechanism that at low reverse voltages PFE is found to be dominant whereas SE is dominant at high reverse voltages. The reduced interface state densities at the CoPc/n-Ge interface were observed under illumination than compared to dark.

Investigation of In2SexOy/In2Se3/Si dual-junction photodiode for self-powered broadband photodetection

We report a dual-junction strategy for fabricating a high-performance In2SexOy/In2Se3/Si heterojunction photodiode by oxidizing the epitaxial In2Se3 thin films. The device exhibits a suppressed dark current (4.2 × 10−11 A) and enhanced photocurrent at zero bias, benefiting from the double built-in electric fields. Consequently, it demonstrates excellent and uniform self-powered broadband (255–1050 nm) photodetection performance with the typical responsivity of several hundred mA/W, and detectivity of over 5 × 1011 Jones. Moreover, a fast response speed with a response time of 0.20 ms is achieved. Our investigation offers a potential route to construct full-spectrum photodetectors.

Transparent and conducting p-type (CuS)x:(ZnS)1-x thin films produced by thermal evaporation: An efficient broadband Si heterojunction photodiode

This study demonstrates the viability of the thermal evaporation method to produce transparent and highly conductive p-type (CuS)x:(ZnS)1-x thin films by achieving the highest conductivity value (1.4 × 103 S/cm) reported in this field to date. This places it in direct comparison with n-type transparent conductors. Analysis through X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) unveils nanocomposite structures comprising sphalerite ZnS, chalcocite Cu2S, and covellite CuS nanocrystals in the thin films. The study reveals that transmittance values at a wavelength of 550 nm vary from 84 % to 65 % based on the increasing CuS ratio, establishing thermal-evaporated (CuS)x:(ZnS)1-x thin films as promising candidates for p-type transparent electrodes.Moreover, p+-(CuS)0.49:(ZnS)0.54/n-Si heterojunction photodiodes were also produced.The heterojunction diode exhibited excellent photo-response characteristics in a wide range of wavelengths between 325 and 1170 nm at zero-bias.The responsivity value of the photodiode was as high as 1.44 A/W at the peak wavelength of 912 nm (9.45 mW/cm2) with a high Ion/Ioffratio of 1.45 × 104. Besides, it was shown to have excellent detectivity,response time, and external quantum efficiency (EQE) values corresponding to 2.62 × 1012Jones,8.45 µs, and 244 %, respectively. Most of these values are superior to those even in commercial-grade photodiodes.

Self-powered dual-mode UV detector based on GaN/(BA)<sub>2</sub>PbI<sub>4</sub> heterojunction

As an important part of an intelligent photoelectric system, ultraviolet detector has been widely used in many fields in recent years. The research on self-powered heterojunction photodiode is particularly important. In this work, a dual-mode self-powered GaN/(BA)<sub>2</sub>PbI<sub>4</sub> heterojunction ultraviolet photodiode is prepared and discussed. The GaN film is deposited on sapphire by metal-organic chemical vapor deposition, and then the (BA)<sub>2</sub>PbI<sub>4</sub> film is spin-coated onto the surface of the GaN film to construct a planar heterojunction detector. The X-ray diffraction, energy-dispersive X-ray spectroscopy mapping and scanning electron microscope measurements are used to determine the quality of GaN and (BA)<sub>2</sub>PbI<sub>4</sub> thin films. When the film is illuminated by 365 nm light with a power density of 421 μW/cm<sup>2</sup> at 5 V bias, the responsiveness (<i>R</i>) and external quantum efficiency (EQE) are 60 mA/W and 20%, respectively. In self-powered mode, the rise time (<i>τ</i><sub>r</sub>) and decay time (<i>τ</i><sub>d</sub>) are 0.12 s and 0.13 s, respectively, illustrating the fast photogeneration process and recombination process for photo-excited electron-hole pairs. And, the <i>R</i> is 1.96×10<sup>–4</sup> mA/W, owing to the development of space charge region across the interface of GaN thin film and (BA)<sub>2</sub>PbI<sub>4</sub> thin film. The outcomes of this study unequivocally demonstrate the extensive potential and wide-ranging applicability of self-powered UV photodiodes based on the GaN/(BA)<sub>2</sub>PbI<sub>4</sub> heterojunction configuration. Moreover, this research presents a new concept that provides a novel avenue to the ongoing development of intelligent optoelectronic systems.

Black Phosphorus Molybdenum Disulfide Midwave Infrared Photodiodes with Broadband Absorption-Increasing Metasurfaces.

Black phosphorus (BP) has been established as a promising material for room temperature midwave infrared (MWIR) photodetectors. However, many of its attractive optoelectronic properties are often observable only at smaller film thicknesses, which inhibits photodetector absorption and performance. In this work, we show that metasurface gratings increase the absorption of BP-MoS2 heterojunction photodiodes over a broad range of wavelengths in the MWIR. We designed, fabricated, and characterized metasurface gratings that increase absorption at selected wavelengths or broad spectral ranges. We evaluated the broadband metasurfaces by measuring the room temperature responsivity and specific detectivity of BP-MoS2 photodiodes at multiple MWIR wavelengths. Our results show that broadband metasurface gratings are a scalable approach for boosting the performance of BP photodiodes over large spectral ranges.