Heterostructure Photodetector Research Articles

Transparent and Reusable Nanostencil Lithography for Organic–Inorganic Hybrid Perovskite Nanodevices

AbstractOrganic—inorganic hybrid perovskites have attracted considerable attention for developing novel optoelectronic devices owing to their excellent photoresponses. However, conventional nanolithography of hybrid perovskites remains a challenge because they undergo severe damage in standard lithographic solvents, which prohibits device miniaturization and integration. In this study, a novel transparent stencil nanolithography (t‐SL) technique is developed based on focused ion beam (FIB)‐assisted polyethylene terephthalate (PET) direct patterning. The proposed t‐SL enables ultrahigh lithography resolution down to 100 nm and accurate stencil mask alignment. Moreover, the stencil mask can be reused more than ten times, which is cost‐effective for device fabrication. By applying this lithographic technique to hybrid perovskites, a high‐performance 2D hybrid perovskite heterostructure photodetector is fabricated. The responsivity and detectivity of the proposed heterostructure photodetector can reach up to 28.3 A W−1 and 1.5 × 1013 Jones, respectively. This t‐SL nanolithography technique based on FIB‐assisted PET direct patterning can effectively support the miniaturization and integration of hybrid‐perovskite‐based electronic devices.

Ultraviolet Photoresponse Enhancement of Graphene/Al x O y -NPs/MoS2 Heterostructure Photodetectors

Molybdenum disulfide (MoS2) has been widely used to fabricate the photodetectors in recent years due to its excellent optical properties. However, the narrow detection bandwidth of MoS2 films limits their applications. Here, a thin Al film was deposited on the surface of MoS2 and naturally oxidized to form the AlxOy nanoparticles (AlxOy-NPs) for the enhanced performance of graphene/AlxOy-NPs/MoS2 heterostructure photodetectors. The material analyses were performed to confirm the formation of AlxOy-NPs on MoS2 and its influence on light absorption. Additionally, the photoresponse of graphene/AlxOy-NPs/MoS2 heterostructure photodetectors was investigated, and found that the localized surface plasmon resonance (LSPR) was induced in the ultraviolet-A (UV-A) band (365 nm), increasing the photocurrent owing to the p-type nature of graphene channel with the recombination of excited electrons from AlxOy-NPs/MoS2 to enhance the photoresponse. The photodetectors with an AlxOy film of 0.5 nm presented a UV-A light detection capability with the photoresponsivity, quantum efficiency, and detectivity of 6.24 A/W, 2120%, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.79\times 10^{{10}}$ </tex-math></inline-formula> Jones, respectively, at the optical power of 10 mW/cm2. Thus, the proposed one-step growth method of AlxOy-NPs on MoS2 films to fabricate the graphene/AlxOy-NPs/MoS2 heterostructure photodetectors with excellent photoresponse can facilitate the development of novel 2-D material photodetectors in future.

Hydrothermally grown SnS2/Si nanowire core-shell heterostructure photodetector with excellent optoelectronic performances

Core-shell nanowire heterostructure is a new architecture for photodetector application with enlarged active surface area enhancing light absorption and photodetector performance. As an emanating coating material, SnS2 has a growing interest in next-generation optoelectronic materials. Here, we reported the enhanced optoelectronic performance of the hydrothermally grown SnS2 and Si nanowire (SiNWs) core–shell heterostructure. Hydrothermally grown SnS2 on Si nanowire creates a uniform coating over the entire surface of nanowires which enhances the heterostructure’s effective junction area and improves optoelectronic performance over the broad spectral range (300 – 1100 nm). Specially, under 340 nm illumination, the core–shell photodetector exhibits large responsivity (∼383 A/W) and extremely high external quantum efficiency (∼2 × 105 %) at very low optical power (∼20 nW/mm2). This SnS2/SiNWs core–shell heterostructure with significantly improved optoelectronic performance will be favourable for the development of photodetector with an ability to work with extremely high efficiency.

Enhanced photoresponse of a dielectric-free suspended WSe2–ReS2 heterostructure photodetector

Optoelectronic devices based on layered two-dimensional (2D) van der Waals (vdW) semiconductors and their heterostructures suffer from carrier scattering, trapping, and trap-assisted recombination-generation at the vdW channel/dielectric interface. In this work, we demonstrate improved photoresponse of a dielectric-free, suspended WSe2 (p)-ReS2 (n) heterostructure photodetector in comparison to an hBN dielectric-supported structure fabricated over a common local Au back gate. The dielectric-free suspension helps in eliminating optical losses at the 2D channel–dielectric interface and optical absorption loss in the dielectric itself as the metal (gold) gate aids in reflecting the incident light to enhance absorption in the 2D heterostructure. The increase in photocurrent increases with incident illumination power and is consistent over a wide range of wavelengths. Suspension of 2D layered materials, thus, paves the route for harnessing their intrinsic properties for next generation photodetection applications.

Monolayer Graphene-MoSSe van der Waals Heterostructure for Highly Responsive Gate-Tunable Near-Infrared-Sensitive Broadband Fast Photodetector.

Transition metal dichalcogenides (TMDCs) are potential two-dimentional materials as natural partners of graphene for highly responsive van der Waals (vdW) heterostructure photodetectors. However, the spectral detection range of the detectors is limited by the optical bandgap of the TMDC, which acts as a light-absorbing medium. Bandgap engineering by making alloy TMDC has evolved as a suitable approach for the development of wide-band photodetectors. Here, broadband (visible to near-infrared) photodetection with high sensitivity in the near-infrared region is demonstrated in a MoSSe/graphene heterostructure. In the ambient environment, the photodetector exhibits high responsivity of 0.6 × 102 A/W and detectivity of 7.9 × 1011 Jones at 800 nm excitation with a power density of 17 fW/μm2 and 10 mV source-drain bias. The photodetector shows appreciable responsivity in self-bias mode due to nonuniform distribution of MoSSe flakes on the graphene layer between the source and drain end and the asymmetry between the two electrodes. Time-dependent photocurrent measurements show fast rise/decay times of ∼38 ms/∼48 ms. A significant gate tunability on the efficiency of the detector has been demonstrated. The device is capable of low power detection and exhibits high operational frequency, gain, and bandwidth. Thus, the MoSSe/graphene heterostructure can be a promising candidate as a high-speed and highly sensitive near-infrared photodetector capable of operating at ambient conditions with low energy consumption.

Highly Responsive Mid-Infrared Metamaterial Enhanced Heterostructure Photodetector Formed out of Sintered PbSe/PbS Colloidal Quantum Dots.

Efficient and simple-to-fabricate light detectors in the mid infrared (MIR) spectral range are of great importance for various applications in existing and emerging technologies. Here, we demonstrate compact and efficient photodetectors operating at room temperature in a wavelength range of 2710-4250 nm with responsivities as high as 375 and 4 A/W. Key to the high performance is the combination of a sintered colloidal quantum dot (CQD) lead selenide (PbSe) and lead sulfide (PbS) heterojunction photoconductor with a metallic metasurface perfect absorber. The combination of this photoconductor stack with the metallic metasurface perfect absorber provides an overall ∼20-fold increase of the responsivity compared against reference sintered PbSe photoconductors. More precisely, the introduction of a PbSe/PbS heterojunction increases the responsivity by a factor of ∼2 and the metallic metasurface enhances the responsivity by an order of magnitude. The metasurface not only enhances the light-matter interaction but also acts as an electrode to the detector. Furthermore, fabrication of our devices relies on simple and inexpensive methods. This is in contrast to most of the currently available (state-of-the-art) MIR photodetectors that rely on rather expensive as well as nontrivial fabrication technologies that often require cooling for efficient operation.

Low‐Temperature Crystallized and Flexible 1D/3D Perovskite Heterostructure with Robust Flexibility and High EQE‐Bandwidth Product

AbstractAll‐inorganic perovskite cesium lead triiodide (CsPbI3) has attracted much attention among the perovskite family due to its excellent optoelectronic properties and chemical stability. However, the high‐temperature crystallization process makes CsPbI3 less compatible with commercially flexible substrates, limiting its application into flexible optoelectronics. Here, a cation of 1‐(3‐aminopropyl)‐2pyrrolidinone (APP) is reported that can form 1D (APP)PbI3 perovskite as templates, and significantly reduce the CsPbI3 black‐phase transition energy with a low annealing temperature of 75 °C, which further enables a flexible (APP)PbI3/γ‐CsPbI3 (1D/3D) heterostructure photodetector on ITO/PET substrate. A high external quantum efficiency (EQE) greater than 2377% is observed along the orientated 1D/3D heterostructure. The high gain and low noise result in a high specific detectivity (D*) over 1012 Jones under −0.6 V low bias. The optimized device structure brings a high EQE × bandwidth product of 119 kHz under a low driving bias. Due to the high toughness of orientated APP+ ions and the face‐connected [PbI3]− chains structure as a strong energy absorber, the flexible photodetector also shows excellent phase stability and impressive flexibility, remaining &gt;90% initial responsivity after over 20 000 times bending with potential flexible imaging application in harsh environments.

Two-dimensional Bi2S3/MoS2 van der Waals heterostructure for self-powered photodetectors

Two-dimensional (2D) semiconductor materials have been widely applied for optoelectronic devices, but fast charge recombination severely affects device performance. The construction of a 2D heterostructure is a proven strategy for effectively reducing carrier recombination. 2D Bi2S3/MoS2 heterostructure is prepared by a sequential vapor deposition method. This heterostructure displays a fast response/recovery time of 4/15 ms and a high responsivity of 218.3 μA W−1. The improved photodetection performance is mainly ascribed to the internal electric field-induced efficient charge transfer in the type-II Bi2S3/MoS2 heterostructure. This study provides a guideline to extend other heterostructure photodetectors and improve the photodetection performance.

A waveguide-integrated self-powered van der Waals heterostructure photodetector with high performance at the telecom wavelength.

Two-dimensional (2D) materials are attractive candidates for high-performance photodetectors due to their wide operating wavelength and potential to integrate with silicon photonics. However, due to their limited atomic thickness and short carrier lifetime, they suffer from high driving source-drain voltages, weak light-matter interactions and low carrier collection efficiency. Here, we present a high-performance van der Waals (vdWs) heterostructure-based photodetector integrated on a silicon nitride photonic platform combining p-type black phosphorus (BP) and n-type molybdenum disulfide (MoS2). Owing to the efficient carrier separation process and dark current suppression at the junction interface of the vdWs heterostructure, high photodetectivity and a fast response speed can be achieved. A fast response time (∼2.08/3.54 μs), high responsivity (11.26 mA W-1), and a high light on/off ratio (104) operating in the near-infrared telecom band are obtained at zero bias. Our research highlights the great potential of the high-efficiency waveguide-integrated vdWs heterojunction photodetector for integrated optoelectronic systems, such as high-data-rate interconnects operated at standardized telecom wavelengths.

A two-dimensional Te/ReS2 van der Waals heterostructure photodetector with high photoresponsivity and fast photoresponse.

Two-dimensional (2D) semiconductors are the building blocks for high-performance optoelectronic devices. However, the performance of photoconductive photodetectors based on 2D semiconductors is hampered by low photoresponsivity and large dark current. Herein, a van der Waals heterostructure (vdWH) composed of rhenium disulfide (ReS2) and tellurium (Te) is fabricated. The Te/ReS2 vdWH photodetector exhibits a sensitive and broadband photoresponse and has high photoresponse on/off ratios under ultraviolet and visible light illumination, especially over 102 in visible light. The Te/ReS2 vdWH photodetector achieves the responsivity of 7.9 A W-1 at 365 nm, 3.02 A W-1 at 450 nm, 2.37 A W-1 at 532 nm, and 2.45 A W-1 at 660 nm. In addition, the device achieves a high specific detectivity of 1011 Jones and a fast photoresponse speed of 11.9 μs. Such high responsivity could be attributed to the efficient absorption of phonons by the Te/ReS2 vdWH and the high-quality heterostructure interfaces with a small amount of trap states. The highly crystalline structure of Te/ReS2 with a low density of defects reduces the grain boundary scattering, leading to the rapid diffusion of charge carriers. Moreover, the Te/ReS2 vdWH device exhibits a photovoltaic effect and can be employed as a self-powered photodetector (SPPD), which is sensitive to visible light of 450 nm, 532 nm, and 660 nm. Our findings demonstrate that the Te/ReS2 vdWH photodetector is an ideal building block for the next-generation electronic and optoelectronic devices in practical applications.

Ultrahigh responsive negative photoconductivity photodetector based on multilayer graphene/InSe van der Waals heterostructure

Negative photoconductivity (NPC) exhibits great potential in the field of photodetection due to low power consumption and high response. Herein, the photodetectors based on InSe and multilayer graphene (MLG)/InSe van der Waals heterostructure are fabricated. The InSe photodetector shows positive photoconductivity (PPC) behavior, while the MLG/InSe photodetector exhibits NPC behavior. The ultrahigh responsivity (1.88×10 5 A/W) is achieved for the NPC MLG/InSe photodetector, which is five orders of magnitude higher than that of the sole InSe photodetector based on PPC (6.97 A/W). The MLG/InSe photodetector also shows a high external quantum efficiency (6.41×10 7 %) and a fast response time (22 ms). The proposed high-performance MLG/InSe heterostructure photodetector based on NPC for low-dimensional materials may extend applications in future optoelectronic devices.

Interfacial Assembly of Ti3 C2 Tx /ZnIn2 S4 Heterojunction for High-Performance Photodetectors.

Two-dimensional (2D) materials have emerged as prospective candidates for electronics and optoelectronics applications as they can be easily fabricated through liquid exfoliation and used to fabricate various structures by further subsequent processing methods in addition to their extraordinary and unique optoelectronic properties. Herein, the Ti3 C2 Tx /ZIS heterostructure with nanometer-thick Ti3 C2 Tx -MXene and ZnIn2 S4 (ZIS) films is fabricated by successive interfacial assembly of liquid exfoliated 2D MXene and ZnIn2 S4 nanoflakes. Benefiting from the superior light-harvesting capability and low dark current of ZnIn2 S4 , the limited absorbance, large scattering coefficient, and high dark current disadvantages of MXene are ameliorated. Meanwhile, the separation and transport of photogenerated carriers in ZnIn2 S4 are improved due to the excellent electrical conductivity of Ti3 C2 Tx nanoflakes. As a result, the as-prepared Ti3 C2 Tx /ZIS heterostructure photodetector has excellent optoelectronic characteristics in terms of a high responsivity of 1.04mAW-1 , a large specific detectivity up to 1×1011 Jones, a huge on/off ratio at around 105 , and an ultralow dark current at ≈10-12 A. This work demonstrates a convenient method to construct heterostructured photodetectors by liquid exfoliated 2D nanoflakes, the as-fabricated Ti3 C2 Tx /ZIS heterostructured photodetectors show promising application potential for low-cost, reliable, and high-performance photodetectors.

3C-SiC/Si heterostructure for self-powered multiband (UV-VIS) photodetection applications

This study reports a self-powered 3C-SiC/Si heterostructure photodetector in both metal-semiconductor-metal (MSM) and heterojunction (HET) configurations and capable of operating under ultraviolet and visible light (UV–vis). The single crystalline 3C-SiC thin film was grown epitaxially on a Si (111) substrate by employing a two-step growth process. MSM configuration exhibited a peak responsivity of 0.334 A W−1 and a specific detectivity of 5.4 × 1011 cm.Hz1/2.W−1 (Jones) under white light illumination. However, in the UV region, photocurrent showed an increasing behavior with a decrease in the UV wavelength from 365 nm to 254 nm. The peak responsivity and specific detectivity values of the HET configuration were also determined under white light illumination with 0.167 A W−1 and 4.4 × 1011 Jones, respectively. Furthermore, both devices exhibited very fast rise and decay times as 3.8 ms and 3.6 ms for the MSM, and 6 ms and 8 ms for the HET configuration (fastest reported on 3C-SiC). In brief, our self-powered 3C-SiC/Si heterostructure with multiband (UV–vis) photodetection sensitivity and fast speed could offer new solutions for the eco-friendly and sustainable optoelectronic applications.

A high-performance and broadband two-dimensional perovskite-based photodetector via van der Waals integration

Van der Waals (vdW) integration of two-dimensional (2D) nanosheets provides the possibility to design optoelectronic devices with extended functionality in a controllable manner. Here, by leveraging the appropriate energy band alignment and the high-efficiency charge transfer at the junction, we construct the MoS2/graphene/2D-perovskite vdW heterostructure, which realizes the highly sensitive and broadband photodetection. Particularly, at the near-infrared (NIR) wavelength (λ = 1550 nm), the heterostructure photodetector shows a balanced trade-off between the high responsivity (&amp;gt;3000 A/W) and fast response time (&amp;lt;1 ms), outperforming the previously reported NIR photodetectors based on all-inorganic vdW heterostructures. Our work not only extends the response wavelength of the 2D hybrid perovskite-based photodetector to the NIR range, but also offers additional insight into optoelectronic devices via vdW integration engineering.

Graphene/Quantum Dot Heterostructure Photodetectors: From Material to Performance

AbstractOwing to its high carrier mobility, electrical conductivity, and thermal/chemical stability, graphene is an ideal candidate material for photodetection. However, the weak light absorption of graphene significantly limits its practical applications in photodetectors. Quantum dots, with strong light‐absorption capacity and well‐adjustable band gap, are widely hybridized with graphene to realize wide‐range and intense light absorption for effective photodetection. A detailed literature review on graphene/quantum dot heterostructure photodetectors is in urgent need to clearly point out the fundamentals, material synthesis methods, and performance engineering strategies. Here, first, the significance of graphene/quantum dot heterostructure photodetectors, from the mechanism to performance indicators, is systematically discussed. Second, different synthesis methodologies for the graphene/quantum dot heterostructure are overviewed. Additionally, the engineering strategies, including surface treatment, chemical doping, and size modification, to tune the photoelectric performance are critically commented. Finally, challenges and outlook for the development of graphene/quantum dot heterostructure photodetectors are pointed out.

Lateral Heterostructured Vis-NIR Photodetectors with Multimodal Detection for Rapid and Precise Classification of Glioma.

Precise diagnosis of the boundary and grade of tumors is especially important for surgical dissection. Recently, visible and near-infrared (Vis-NIR) absorption differences of tumors are demonstrated for a precise tumor diagnosis. Here, a template-assisted sequential printing strategy is investigated to construct lateral heterostructured Vis-NIR photodetectors, relying on the up-conversion nanoparticles (UCNPs)/perovskite arrays. Under the sequential printing process, the synergistic effect and co-confinement are demonstrated to induce the UCNPs to cover both sides of the perovskite microwire. The side-wrapped lateral heterogeneous UCNPs/perovskite structure exhibits more satisfactory responsiveness to Vis-NIR light than the common fully wrapped structure, due to sufficient visible-light-harvesting ability. The Vis-NIR photodetectors with R reaching 150 mA W-1 at 980 nm and 1084 A W-1 at 450 nm are employed for the rapid classification of glioma. The detection accuracy rate of 99.3% is achieved through a multimodal analysis covering the Vis-NIR light, which provides a reliable basis for glioma grade diagnosis. This work provides a concrete example for the application of photodetectors in tumor detection and surgical diagnosis.

High detectivity graphene/si heterostructure photodetector with a single hydrogenated graphene atomic interlayer for passivation and carrier tunneling

Hydrogenated graphene is easy to prepare and chemically stable. Besides, hydrogenation of graphene can open the band gap, which is vital for electronic and optoelectronic applications. Graphene/Si photodetector (PD) has been widely studied in imaging, telecommunications, and other fields. The direct contact between graphene and Si can form a Schottky junction. However, it suffers from poor interface state, where the carrier recombination at the interface causes serious leakage current, which in turn leads to a decrease in the detectivity. Hence, in this study, hydrogenated graphene is used as an interfacial layer, which passivates the interface of graphene/Si (Gr/Si) heterostructure. Besides, the single atomic layer thickness of hydrogenated graphene is also crucial for the tunneling transport of charge carriers and its suitable energy band position reduces the recombination of carrier. The fabricated graphene/hydrogenated-graphene/Si (Gr/H–Gr/Si) heterostructure PD showed an extremely low dark current about 10−7 A. As a result, it had low noise current and exhibited a high specific detectivity of ∼2.3 × 1011 Jones at 0 V bias with 532 nm laser illumination. Moreover, the responsivity of the fabricated PD was found to be 0.245 A W−1 at 532 nm illumination with 10 μW power. These promising results show a great potential of hydrogenated graphene to be used as an interface passivation and carrier tunneling layer for the fabrication of high-performance Gr/Si heterostructure PDs.

Vertical Barrier Heterostructures for Reliable, Robust, and High-Performance Ultraviolet Detection.

Photodetectors based on low-dimensional materials usually suffer from serious optical power-dependent photoresponse and low reliability, particularly in the ultraviolet regime. The barrier photodetector is an effective and reliable strategy where the barrier layer can block the low-energy charge carriers while allowing for a flow of the high-energy photocarriers. Here, vertical barrier heterostructure photodetectors (VBHPs), consisting of a graphene bottom electrode, a MoS2 light absorber, and an h-BN energy barrier, for reliable, robust, and high-performance ultraviolet detection are reported. The asymmetric barrier distribution in the conduction/valence band at the MoS2 /h-BN interface results in an ultralow noise current of 1.69 × 10-15 A Hz-1/2 at room temperature, stable photo on/off states exceeding 104 cycles at 300 K and 400 K, a light power-independent high responsivity of 416.2 mA W-1 at 360 nm, a high photo on-off ratio of 1.2 × 105 at 360 nm, high measured detectivities (3.2 × 1010 Jones at 266 nm and 9.9 × 1010 Jones at 360nm), and wide linear dynamic ranges. The VBHPs show a high potential for new-type reliable ultraviolet detection.

Spin-Coating and Aerosol Spray Pyrolysis Processed Zn1-xMgxO Films for UV Detector Applications.

A series of Zn1−xMgxO thin films with x ranging from 0 to 0.8 were prepared by spin coating and aerosol spray pyrolysis deposition on Si and quartz substrates. The morphology, composition, nano-crystalline structure, and optical and vibration properties of the prepared films were studied using scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD), and optical and Raman scattering spectroscopy. The optimum conditions of the thermal treatment of samples prepared by spin coating were determined from the point of view of film crystallinity. The content of crystalline phases in films and values of the optical band gap of these phases were determined as a function of the chemical composition. We developed heterostructure photodetectors based on the prepared films and demonstrated their operation in the injection photodiode mode at forward biases. A device design based on two Zn1−xMgxO thin films with different x values was proposed for extending the operational forward bias range and improving its responsivity, detectivity, and selectivity to UV radiation.

MXene‐Germanium Schottky Heterostructures for Ultrafast Broadband Self‐Driven Photodetectors

AbstractA novel 2D layered material Ti3C2Tx (MXene) is favored by researchers in the application field of optoelectronics due to its tunable work function, great light transmittance, and excellent electrical conductivity. In this work, Ti3C2Tx/n‐germanium (MXene/n‐Ge) Schottky heterostructures are fabricated and investigated. Schottky contacts of MXene with n‐Ge are identified by ultraviolet photoelectron spectroscopy (UPS). Based on the MXene/n‐Ge Schottky junctions, an ultrafast, broadband, and self‐powered photodetector is demonstrated and studied. The MXene/n‐Ge device exhibits excellent photoresponse from ultraviolet to near‐infrared light illumination. In particular, it shows an excellent on/off ratio (≈104), a high responsivity (3.14 A/W), a larger specific detectivity (2.14 × 1011 Jones), and an ultrafast response speed (trise of 1.4 µs and tdecay of 4.1 µs). Moreover, the MXene/n‐Ge Schottky heterostructure photodetector also shows excellent low‐temperature work characteristics of 73 K. It is believed that this work will attract more researchers’ attention to MXene in the field of optoelectronic devices.