Infrared Photodetectors Research Articles

Sensitive Filter‐Free Narrowband Infrared Photodetectors for Weak Light Detection and Ranging

AbstractLight detection and ranging (Lidar), which utilizes scattered near‐infrared (NIR) light to identify objects, has shown great potential in remote sensing, autonomous driving, robotic vision, etc. However, the intensity of the scattered NIR light is significantly reduced, placing stringent demands on the selectivity and fast response of the sensing. Even though optical filters can be used to select weak signals, the photon losses arising from additional interfaces are inevitable, thus reducing the signal‐to‐noise ratio (SNR). In this work, a series of organic narrowband photodetectors are constructed with tunable and selective responses from 700 to 950 nm with a minimum full‐width‐at‐half‐maximum (FWHM) of ≈30 nm. To enhance response sensitivity and speed, delicate and compact photodiode architecture is applied through comprehensive device engineering. As a result, the detectors possess a sensitive response to weak NIR light with a detection limit of 3 nW, and response rise time (τr) and decay time (τd) of ≈24 ns and ≈1.3 µs, respectively. Moreover, a proof‐of‐concept Lidar based on these organic photodetectors is demonstrated with a distance resolution of ≈10 cm, which further confirms the great potential in practical application.

Polarization‐Sensitive Photodetector Based on Quasi‐1D (TaSe4)2I Nanowire Response to 10.6 µm

AbstractPolarization‐sensitive infrared (IR) photodetection plays an important role in fiber optic communication, environmental monitoring, and remote sensing imaging. Semiconductors with quasi‐1D crystal structures exhibit unique optical and electrical properties due to their 1D carrier transport channels and large surface area‐to‐volume ratio, offering the possibility of high‐performance photodetectors with high photogain (G), polarization sensitivity photodetection. Herein, an ultra‐broadband photodetection (405 nm–10.6 µm) based on a quasi‐1D (TaSe4)2I single‐crystal nanowire is reported. The (TaSe4)2I photodetector exhibits excellent polarization‐sensitive photodetection, with a high dichroic ratio of Imax/Imin = 2.32 under 637 nm illumination. Notably, the (TaSe4)2I nanowire photodetector exhibits a competitive performance in uncooled mid‐wave infrared (MWIR) detection with a high photoresponsivity (R) of 110.5 AW−1 and specific detectivity (D*) of 4.8 × 1010 cmHz1/2W−1. Moreover, in the long‐wave infrared (LWIR) spectral range, an R of 67.6 mAW−1 is demonstrated at room temperature (RT). The (TaSe4)2I nanowire photodetector enables significant advancements for polarization‐sensitive and uncooled MWIR and LWIR photodetection.

Synergistic-potential engineering enables high-efficiency graphene photodetectors for near- to mid-infrared light

High quantum efficiency and wide-band detection capability are the major thrusts of infrared sensing technology. However, bulk materials with high efficiency have consistently encountered challenges in integration and operational complexity. Meanwhile, two-dimensional (2D) semimetal materials with unique zero-bandgap structures are constrained by the bottleneck of intrinsic quantum efficiency. Here, we report a near-mid infrared ultra-miniaturized graphene photodetector with configurable 2D potential well. The 2D potential well constructed by dielectric structures can spatially (laterally and vertically) produce a strong trapping force on the photogenerated carriers in graphene and inhibit their recombination, thereby improving the external quantum efficiency (EQE) and photogain of the device with wavelength-immunity, which enable a high responsivity of 0.2 A/W–38 A/W across a broad infrared detection band from 1.55 to 11 µm. Thereafter, a room-temperature detectivity approaching 1 × 109 cm Hz1/2 W−1 is obtained under blackbody radiation. Furthermore, a synergistic effect of electric and light field in the 2D potential well enables high-efficiency polarization-sensitive detection at tunable wavelengths. Our strategy opens up alternative possibilities for easy fabrication, high-performance and multifunctional infrared photodetectors.

Dicarboxylic Acid-Assisted Surface Oxide Removal and Passivation of Indium Antimonide Colloidal Quantum Dots for Short-Wave Infrared Photodetectors.

Heavy-metal-free III-V colloidal quantum dots (CQDs) are promising materials for solution-processed short-wave infrared (SWIR) photodetectors. Recent progress in the synthesis of indium antimonide (InSb) CQDs with sizes smaller than the Bohr exciton radius enables quantum-size effect tuning of the band gap. However, it has been challenging to achieve uniform InSb CQDs with band gaps below 0.9 eV, as well as to control the surface chemistry of these large-diameter CQDs. This has, to date, limited the development of InSb CQD photodetectors that are sensitive to 1400 nm light. Here we adopt solvent engineering to facilitate a diffusion-limited growth regime, leading to uniform CQDs with a band gap of 0.89 eV. We then develop a CQD surface reconstruction strategy that employs a dicarboxylic acid to selectively remove the native In/Sb oxides, and enables a carboxylate-halide co-passivation with the subsequent halide ligand exchange. We find that this strategy reduces trap density by half compared to controls, and enables electronic coupling among CQDs. Photodetectors made using the tailored CQDs achieve an external quantum efficiency of 25 % at 1400 nm, the highest among III-V CQD photodetectors in this spectral region.

Performance of LWIR to VLWIR barrier photodetectors based on M-structure superlattices.

Antimonide superlattice materials with tunable energy bands, high electron mobility, and easy attainment of good uniformity in large-area materials, are considered to be the material of choice for third-generation infrared photodetectors. Based on energy band engineering, this paper designs a series of long-wave infrared(LWIR) to very-long-wave infrared(VLWIR) photodetectors by employing M-structure superlattice(M-SL) as both absorber layer and barrier layer. The photodetectors' performances at different temperatures are simulated in this manuscript. At 77K, while minimizing the lattice mismatch, effectively suppresses the dark current of the device which can be as low as 1× 10-8A/cm2, with a quantum efficiency reaching 20.85% and normalized detectivity achieves 4.78×1011 cm·Hz1/2/W for LWIR photodetector with a cutoff wavelength of 11.1 μm. For the VLWIR photodetector with a cutoff wavelength of 16.7 μm, the corresponding figures are 1×10-6A/cm2, 16.77% and 3.09×1010 cm·Hz1/2/W, respectively.

Suppressing the Dark Current While Improving the Quantum Efficiency in Shortwave Infrared Organic Photodetectors Through Naphthalenediimide‐Based Interlayer

AbstractThe significance of shortwave infrared (SWIR) photodetectors spans across various applications. Nevertheless, the limited spectral response of silicon‐based photodetectors and the high cost associated with materials like germanium (Ge) have impeded the widespread adoption of SWIR sensors, particularly in the realm of consumer electronics. This study explores the transformative impact of incorporating a cross‐linkable naphthalenediimide (c‐NDI) as both an electron transporting layer and a hole blocking layer in organic photodetectors (OPDs). The introduction of c‐NDI as an interlayer leads to substantial enhancements in SWIR OPD performance, particularly in terms of reducing dark current and augmenting external quantum efficiency. These improvements are most notable in ultra‐narrow bandgap SWIR systems, where c‐NDI demonstrates superior hole‐blocking capabilities. Besides, OPDs with c‐NDI interlayers also exhibit exceptional stability over time when compared to OPDs based on zinc oxide interlayer, underscoring c‐NDI‘s versatility as an interlayer. Most importantly, when compared to a commercially available Ge photodetector, c‐NDI‐based OPD demonstrates competitive detectivity, achieving 2.67 × 1011 Jones at a wavelength of 1300 nm. This performance even surpasses that of the Ge photodetector, highlighting the substantial potential of OPDs for SWIR imaging applications.

Degenerately doped metal oxide nanocrystals for infrared light harvesting: insight into their plasmonic properties and future perspectives.

The tuneability of the localized surface plasmon resonance (LSPR) of degenerately doped metal oxide (MOX) nanocrystals (NCs) over a wide range of the infrared (IR) region by controlling NC size and doping content offers a unique opportunity to develop a future generation of optoelectronic and photonic devices like IR photodetectors and sensors. The central aim of this review article is to highlight the distinctive and remarkable plasmonic properties of degenerately or heavily doped MOX nanocrystals by reviewing the comprehensive literature reported so far. In particular, the literature of each MOX NC, i.e. ZnO, CdO, In2O3, and WO3 doped with different dopants, is discussed separately. In addition to discussion of the most commonly used colloidal synthesis approaches, the ultrafast dynamics of charge carriers in NCs and the extraction of LSPR-assisted hot-carriers are also discussed in detail. Finally, future prospective applications of MOX NCs in IR photodetectors and photovoltaic (PV) self-powered chemical sensors are also presented.

Origin and suppression of dark current for high-performance colloidal quantum dot short-wave infrared photodetectors.

The development of cost-effective and highly sensitive short-wave infrared (SWIR) photodetectors is crucial for the expanding applications of SWIR imaging in civilian applications such as machine vision, autonomous driving, and augmented reality. Colloidal quantum dots (CQDs) have emerged as promising candidates for this purpose, offering distinct advantages over traditional III-V binary and ternary semiconductors. These advantages include the ability to precisely tune the bandgap through size modulation of CQDs and the ease of monolithic integration with Si readout integrated circuits (ROICs) via solution processing. Achieving a minimal reverse bias dark current density (Jd) while maintaining high external quantum efficiency is essential for enhancing the light detection sensitivity of CQDs-based SWIR photodiodes to a level competitive with III-V semiconductors. This challenge has garnered increasing research attention in recent years. Herein, the latest advancements in understanding and mitigating Jd in CQDs SWIR photodiodes are summarized. Starting with a brief overview of the material fundamentals of CQDs, the origins of Jd in CQDs photodiodes, including reverse injection from electrode, diffusion/drift currents, Shockley-Read-Hall generation/recombination currents, trap-assisted tunneling, and shunt/leakage currents, are discussed together with their latest research progresses about strategies adopted to suppress Jd. Finally, a brief conclusion and outlook on future research directions aimed at minimizing Jd and retaining high photoresponse of CQDs SWIR photodiodes are provided.

Electrical Characterization of Type II Superlattice Midwave Infrared Photodetectors Irradiated by Protons

Electrical Characterization of Type II Superlattice Midwave Infrared Photodetectors Irradiated by Protons

Dark Current Mechanisms and Suppression Strategies for Infrared Photodetectors Based on Two‐Dimensional Materials

AbstractNarrow‐bandgap 2D materials and semimetals, for example, graphene, black phosphorus (BP), tellurium (Te), and some novel transition metal dichalcogenides (TMDs), have been demonstrated to be promising building blocks for constructing next‐generation state‐of‐the‐art infrared (IR) photodetectors. However, these devices suffer from a significant dark current, primarily attributed to the intrinsic thermal excitation‐induced high carrier concentration. Suppressing the dark current is an essential issue in pursuing higher specific detectivity of IR photodetectors. Here, the authors demonstrate recent advances in suppressing dark current for 2D IR photodetectors. First, a brief insight into the dark current composition and mechanisms of 2D IR photodetectors is illustrated. Then, the varied band alignment for blocking dark current by the interfacial barrier is discussed. Next, localized electric field modulation by applying a gate voltage and ferroelectric materials is discussed. This method can effectively tune the concentration and distribution of carriers in the device conductive channel. Following that, interfacial engineering is summarized, by which interfacial defects can be passivated and interlayer defect‐induced dark current can be suppressed. Finally, the challenges and an outlook are delivered for developing state‐of‐the‐art IR photodetectors.

Performance study of short-wave infrared photodetectors based on InAs/GaSb/AlSb superlattice

This study investigates the performance of infrared photodetectors through variable temperature tests, specifically examining dark current, light current, and capacitance. The reduction of dark current and the increase in carrier lifetimes are crucial for enabling the utilization of infrared photodetectors in complex environments. By conducting tests and analyses on high-performance detectors, the physical mechanisms governing carrier transport processes can be obtained. In order to elucidate the characteristics of InAs/GaSb/AlSb type-II superlattices, a short-wave infrared (SWIR) photodetector exhibiting low dark current and low saturation bias voltage is designed and fabricated.

Charge Management Enables Efficient Spontaneous Chromatic Adaptation Bipolar Photodetector.

Solution-processed photodetectors have emerged as promising candidates for next-generation of visible-near infrared (vis-NIR) photodetectors. This is attributed to their ease of processing, compatibility with flexible substrates, and the ability to tune their detection properties by integrating complementary photoresponsive semiconductors. However, the limited performance continues to hinder their further development, primarily influenced by the difference of charge transport properties between perovskite and organic semiconductors. In this work, a perovskite-organic bipolar photodetectors (PDs) is introduced with multispectral responsivity, achieved by effectively managing charges in perovskite and a ternary organic heterojunction. The ternary heterojunction, incorporating a designed NIR guest acceptor, exhibits a faster charge transfer rate and longer carrier diffusion length than the binary heterojunction. By achieving a more balanced carrier dynamic between the perovskite and organic components, the PD achieves a low dark current of 3.74nAcm-2 at -0.2V, a fast response speed of <10 µs, and a detectivity of exceeding 1012 Jones. Furthermore, a bioinspired retinotopic system for spontaneous chromatic adaptation is achieved without any optical filter. This charge management strategy opens up possibilities for surpassing the limitations of photodetection and enables the realization of high-purity, compact image sensors with exceptional spatial resolution and accurate color reproduction.

Topological insulator photodetectors in HOT infrared detector family

The past decade witnessed the emergence of a new generation of room-temperature infrared detectors based on low-dimensional solids. Among these are topological insulating materials. The present work aims to evaluate this class of photodetectors in the so-called high-temperature infrared (high operating temperature) photodetector family. Their performance, such as current responsivity and detectivity, are compared with available HgCdTe photodiodes, interband quantum cascade photodetectors, colloidal quantum dot detectors, and two-dimensional transition metal dichalcogenides.

Comprehensive characterization of InAs/GaSb LWIR superlattices with varying InAs layer thickness by molecular beam epitaxy

Type-II superlattice (T2SL) detectors represent a promising advancement in long-wavelength infrared (LWIR) photodetector with significant potential across various applications. This study aims to explore the effect of different InAs layer thicknesses on the properties of InAs/GaSb LWIR SLs, which are fabricated by molecular beam epitaxy (MBE). By employing a comprehensive multi-technique analysis, including Atomic Force Microscopy (AFM), X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Energy-Dispersive X-ray Spectroscopy (EDXS), X-ray Photoelectron Spectroscopy (XPS), and Photoluminescence (PL). We substantiate the outstanding surface morphology, high-quality strain-balanced characterization, actual growth thickness assessment, and elemental content analysis using advanced spectroscopy techniques. These results demonstrate comprehensive insights into the 14/7 ML InAs/GaSb SLs elemental composition and distribution, enhancing understanding of superlattice properties for LWIR applications.

Interfacial Engineering of Quantum Dots–Metal–Organic Framework Composite Toward Efficient Charge Transport for a Short‐Wave Infrared Photodetector

AbstractShort‐wave infrared (SWIR) quantum dot (QD)‐converted photodetectors are one of the promising devices used in artificial intelligence and automatic navigation systems. However, compared to semi‐conductor‐type photodetectors, they suffer from poor chemical stability and weak electronic conductivity. In this study, a PbS QD and conductive metal–organic framework (MOF) hybrid composite is designed with SWIR detection capability. The Fourier‐transform infrared spectroscopy confirms the surface modification of PbS QDs with MOF. X‐ray absorption near‐edge structures spectra reveal the chemical bonding between MOF and PbS QDs. Furthermore, 2D grazing‐incidence small‐ and wide‐angle X‐ray scattering is utilized to unveil the particle stacking and the preferred orientation of the PbS@MOF thin film. By integrating the PbS@MOF thin film directly on top of the graphene field effect transistor (FET) device, the chemical stability and photoelectric properties of graphene FET are enhanced, and these are investigated using a focus ion beam with a high‐resolution transmission electron microscope. This study offers a strategy to simultaneously improve the chemical stability and the photoelectronic properties of the nanomaterials as well as contribute to the advancement of a QD‐converted SWIR photodetector.

Asymmetrically Contacted Tellurium Short‐Wave Infrared Photodetector with Low Dark Current and High Sensitivity at Room Temperature

AbstractLarge dark current at room temperature has long been the major bottleneck that impedes the development of high‐performance infrared photodetectors toward miniaturization and integration. Although infrared photodetectors based on layered 2D narrow bandgap semiconductors have shown admirable advantages compared with those based on conventional compounds, which typically suffer from the expensive cryogenic operation, it is still urgent to develop a simple but effective strategy to further reduce the dark current. Herein, a tellurium (Te)‐based infrared photodetector is reported with specifically designed asymmetric electrical contact area. The deliberately introduced asymmetric electrical contact raises the electric field intensity difference in the Te channel near the drain and the source electrodes, resulting in the spontaneous asymmetric carrier diffusion under global infrared light illumination under zero bias. Specifically, the Te‐based photodetector presents promising detector performance at room temperature including a low dark current of ≈1 nA, an ultrahigh photocurrent/dark current ratio of 1.57 × 104, a high specific detectivity (D*) of 3.24 × 109 Jones, and a relatively fast response speed of ≈720 µs at zero bias. The results prove that the simple design of asymmetric electrical contact areas can provide a promising solution to high‐performance 2D semiconductor‐based infrared photodetectors working at room temperature.

Modeling of dark current in semispherical quantum dot structures for infrared photodetection

Due to its tunable heterojunction bandgap and great sensitivity to normal incident illumination, the Quantum Dot Infrared Photodetectors (QDIPs) have received a lot of attention for the purpose of infrared sensing. It could be a very promising replacement for conventional infrared photodetectors made with established technology, including mercury cadmium telluride and quantum well infrared photodetectors. In this work, a model for the dark current in semispherical QDIP has been developed, resolves the primary semiconductor Poisson's and continuity equations, where the wave function and the bound states effects are investigated. In this study, Boltzmann transport equation in the photodetector active layer with embedded QDs is solved using the finite difference time domain method to determine the photodetector carrier mobility and its degradation due the quantum dot scattering. The outcomes of the presented have been contrasted with truncated conical QDIPs showing that smaller volume QDs had less noisy dark current. Investigations have been done into how the semispherical QDIP's dark current characteristics are affected by the QD volume, density, and operating temperature.

Molecular surface programming of rectifying junctions between InAs colloidal quantum dot solids

Heavy-metal-free III-V colloidal quantum dots (CQDs) show promise in optoelectronics: Recent advancements in the synthesis of large-diameter indium arsenide (InAs) CQDs provide access to short-wave infrared (IR) wavelengths for three-dimensional ranging and imaging. In early studies, however, we were unable to achieve a rectifying photodiode using CQDs and molybdenum oxide/polymer hole transport layers, as the shallow valence bandedge (5.0 eV) was misaligned with the ionization potentials of the widely used transport layers. This occurred when increasing CQD diameter to decrease the bandgap below 1.1 eV. Here, we develop a rectifying junction among InAs CQD layers, where we use molecular surface modifiers to tune the energy levels of InAs CQDs electrostatically. Previously developed bifunctional dithiol ligands, established for II-VI and IV-VI CQDs, exhibit slow reaction kinetics with III-V surfaces, causing the exchange to fail. We study carboxylate and thiolate binding groups, united with electron-donating free end groups, that shift upward the valence bandedge of InAs CQDs, producing valence band energies as shallow as 4.8 eV. Photophysical studies combined with density functional theory show that carboxylate-based passivants participate in strong bidentate bridging with both In and As on the CQD surface. The tuned CQD layer incorporated into a photodiode structure achieves improved performance with EQE (external quantum efficiency) of 35% (>1 μm) and dark current density < 400 nA cm-2, a >25% increase in EQE and >90% reduced dark current density compared to the reference device. This work represents an advance over previous III-V CQD short-wavelength IR photodetectors (EQE < 5%, dark current > 10,000 nA cm-2).

DFT Study about the Effect of Doping on the Properties of GaSb Material and Designing of High‐Efficiency Infrared Photodetector

The gallium antimonide (GaSb) material has very attractive electronic and optoelectronic properties which are suitable for next‐generation infrared (IR) photodetector applications. In this work, properties of undoped GaSb material such as density of states, bandstructure, electron density, absorption coefficient, dielectric function, refractive index, and extinction coefficient are calculated using density‐functional theory (DFT). Moreover, the effects of doping with Ge, Sn, and Zn elements on these properties of GaSb material are investigated. It is found that undoped GaSb material exhibits a direct gap of ≈0.72 eV. Among different doping elements, Ge‐doped GaSb produces a very significant enhancement in optical properties. The Ge‐doped GaSb demonstrates a four times higher absorption coefficient in comparison to undoped GaSb in the IR region at 0.8 eV photon energy. GaSb‐based photodetector device is designed using the Solar Cell Capacitance Simulator (SCAPS) 1D tool. The efficiency of the designed photodetector with optimum thicknesses and doping of different layers is found to be improved from 21.34% to 25.91% after incorporating the absorption data set obtained from the DFT calculations. Additionally, the photodetector with optimum parameters demonstrates maximum responsivity of value ≈0.31 A W−1. In the previous findings, it is demonstrated that GaSb is a very suitable material for next‐generation IR photodetector applications.

Infrared HOT Photodetectors: Status and Outlook.

At the current stage of long-wavelength infrared (LWIR) detector technology development, the only commercially available detectors that operate at room temperature are thermal detectors. However, the efficiency of thermal detectors is modest: they exhibit a slow response time and are not very useful for multispectral detection. On the other hand, in order to reach better performance (higher detectivity, better response speed, and multispectral response), infrared (IR) photon detectors are used, requiring cryogenic cooling. This is a major obstacle to the wider use of IR technology. For this reason, significant efforts have been taken to increase the operating temperature, such as size, weight and power consumption (SWaP) reductions, resulting in lower IR system costs. Currently, efforts are aimed at developing photon-based infrared detectors, with performance being limited by background radiation noise. These requirements are formalized in the Law 19 standard for P-i-N HgCdTe photodiodes. In addition to typical semiconductor materials such as HgCdTe and type-II AIIIBV superlattices, new generations of materials (two-dimensional (2D) materials and colloidal quantum dots (CQDs)) distinguished by the physical properties required for infrared detection are being considered for future high-operating-temperature (HOT) IR devices. Based on the dark current density, responsivity and detectivity considerations, an attempt is made to determine the development of a next-gen IR photodetector in the near future.