Distinct Photoresponse Research Articles

Exploring the complementary potential of DVT-Grown InxMo1-xS2 (x = 0.05 & 0.1) for enhanced photoelectrochemical photodetectors and dye degradation

The platform used in this work, InxMo1-xS2 (x = 0.05 & 0.1) nanosheets, allows for exploration of two crucial areas: remediation of the environment and optoelectronic applications. The sonochemical exfoliation approach generated the MoS2 nanosheets. The exfoliated MoS2 has a 2H-hexagonal lattice structure and a P63/mmc space group. The MoS2 nanosheets' lateral shape was observed using transmission electron microscopy (TEM), and their extremely crystalline nature was verified by selected area electron diffraction (SAED). The absorption spectra of MoS₂ nanosheets show unique A and B excitonic resonances. It investigates pulse photo-response characteristics associated with dye degradation methods, emphasizing InxMo1-xS2 (x = 0.05 & 0.1) efficiency in destroying dyes and enabling photocatalytic degradation, particularly with methylene blue (MB) solutions. After 120 min of exposure to light, these nanosheets are effective, breaking down organic pigments. The work also indicates a distinct pulse photoresponse in InxMo1-xS2 (x = 0.05 & 0.1) Nanosheets, increasing their potential as ultrafast photodetectors for optoelectronics. Built-in electrodes produce noticeable photocurrents under 8 mV bias and polychromatic light, demonstrating a strong photovoltaic effect. The In0.05Mo0.95S2 nanosheet-based working electrodes are significantly photovoltaic, with a photocurrent of 3.427 mA under an 8 mV bias and 100 mW/cm2 of polychromatic light. These electrodes have a remarkable peak photoresponsivity of 2.715 A/W under optimum conditions. In the end, this work demonstrates the potential of InxMo1-xS2 (x = 0.05 & 0.1) nanosheets in improving optoelectronic devices and environmentally friendly solutions by revealing when dye degradation and pulse photo-response interact with one another.

P-Type Schottky Contacts for Graphene Adjustable-Barrier Phototransistors.

The graphene adjustable-barriers phototransistor is an attractive novel device for potential high speed and high responsivity dual-band photodetection. In this device, graphene is embedded between the semiconductors silicon and germanium. Both n-type and p-type Schottky contacts between graphene and the semiconductors are required for this device. While n-type Schottky contacts are widely investigated, reports about p-type Schottky contacts between graphene and the two involved semiconductors are scarce. In this study, we demonstrate a p-type Schottky contact between graphene and p-germanium. A clear rectification with on-off ratios of close to 103 (±5 V) and a distinct photoresponse at telecommunication wavelengths in the infrared are achieved. Further, p-type silicon is transferred to or deposited on graphene, and we also observe rectification and photoresponse in the visible range for some of these p-type Schottky junctions. These results are an important step toward the realization of functional graphene adjustable-barrier phototransistors.

Pressure-induced photo-responsiveness enhancement and positive–negative switch in Bi2S3

Bi2S3 has attracted significant interest due to its unique optical, electrical, and photosensitive properties. The utilization of pressure has been substantiated as a proficient technique in modulating the optoelectronic characteristics of functional materials and has garnered increasing attention. In this work, the photoresponse of Bi2S3 upon compression was systematically investigated in combination with in situ photocurrent measurements, Raman spectroscopy, absorption spectroscopy, and density functional theory calculations. Under pressure, Bi2S3 exhibits two distinct photoresponses. Bi2S3 exhibits an obvious positive photoresponse in the pressure range from 0.5 to 9.7 GPa. The photocurrent shows a rapid increase with increasing pressure and reaches the maximum value at 4.0 GPa, which is 5.6 times of the initial value. Interestingly, above 30.3 GPa, Bi2S3 shows a negative photocurrent response, which can be attributed to the photothermal effect caused by pressure-induced metallization phase transition. Our findings provide insight into the modulation of the optoelectronic properties of Bi2S3 and offer more possibilities in the further optimizing design optoelectronic devices based on Bi2S3.

Spray-Coating Thick Films of All-Inorganic Halide Perovskites for Filterless Narrowband Photodetectors.

A significant challenge facing perovskite narrowband photodetectors is making high-quality and thick enough films. Here, we report a facile one-step spray-coating approach to deposit cesium lead halide perovskite thick films for filterless narrowband photodetectors, which exhibited a specific detectivity of 2.43 × 1010 Jones at 655 nm with an fwhm of 25 nm. We demonstrated that both substrate temperature and deposition time during the spray-coating process are key factors that govern the thickness and morphology of perovskite films. The photodetection behavior was dependent on the film thickness, and the narrowband photoresponse was recorded at a 3.9 μm thickness. We discovered that the internal electric field also plays a critical role in determining the narrowband photoresponse behavior. A distinct photoresponse behavior was observed when respectively applying a reverse bias and a forward bias, which is ascribed to the trade-off between the charge-trapping effect and charge extraction under the internal built-in electric field in different biased conditions. Through changing the halogen composition of perovskites from CsPbCl2Br to CsPbI2Br, the peak position of the narrowband spectral photoresponse was observed to shift from 460 to 660 nm. This study not only offers a controllable spray-coating approach to develop thick perovskite films but also provides an important guidance for the rational design of filterless narrowband photodetectors for practical applications in industrial control, visual imaging, and biological sensing.

Water-splitting photoelectrodes consisting of heterojunctions of carbon nitride with a p-type low bandgap double perovskite oxide

Quinary and senary non-stoichiometric double perovskites such as Ba2Ca0.66Nb1.34−x Fe x O6−δ (BCNF) have been utilized for gas sensing, solid oxide fuel cells and thermochemical CO2 reduction. Herein, we examined their potential as narrow bandgap semiconductors for use in solar energy harvesting. A cobalt co-doped BCNF, Ba2Ca0.66Nb0.68Fe0.33Co0.33O6−δ (BCNFCo), exhibited an optical absorption edge at ∼800 nm, p-type conduction and a distinct photoresponse up to 640 nm while demonstrating high thermochemical stability. A nanocomposite of BCNFCo and g-C3N4 (CN) was prepared via a facile solvent-assisted exfoliation/blending approach using dichlorobenzene and glycerol at a moderate temperature. The exfoliation of g-C3N4 followed by wrapping on perovskite established an effective heterojunction between the materials for charge separation. The conjugated 2D sheets of CN enabled better charge migration resulting in increased photoelectrochemical performance. A blend composed of 40 wt% perovskites and CN performed optimally, whilst achieving a photocurrent density as high as 1.5 mA cm−2 for sunlight-driven water-splitting with a Faradaic efficiency as high as ∼88%.

Wide-spectrum photodetector constructed on a centimeter-scale flexible SnSe2 film using a new one-step strategy

Two-dimensional (2D) materials attached with flexible substrates enable possibilities to apply their superior properties to the rapidly increasing demand for foldable displays and wearable biosensors in the internet-of-things technology. However, previous two-step strategy to construct the flexible devices, namely first obtaining 2D materials elsewhere and then transferring them onto flexible substrates, can cause huge problems, including irreversibly undermining the device performance and limiting the material size. Here we propose a new one-step strategy (other than the liquid phase processing and low temperature synthesis methods), namely directly depositing appropriate 2D materials onto flexible substrates, which involves no transferring and can maintain the crystal quality and properties to the greatest extent. More importantly, this strategy in principle has no limit in the film size, hence removing a main obstacle for the practical use of flexible films, such as complex logic operations and large-area optoelectronic applications. Using this strategy, a centimeter-scale SnSe2 film is directly grown on polydimethylsiloxane, which is characterized as a uniform, out-of-plane oriented and semiconducting film that is robust to deformations. Based on the film, a flexible photodetector is fabricated and distinct photoresponse to a broad spectrum of light (405–830 nm) is observed, with remarkable technical parameters.

Vertically Stacked High Mobility GeSi nGAAFETs

Si FinFET architecture has been used in mass production in the industry for advanced technology nodes. Thin and tall fin for high drive current is needed for further scaling by FinFETs. However, fin aspect ratio and lithography limitation may be problematic issues. Recently, vertically stacked channel GAAFETs become good candidates to achieve better power-performance properties than FinFETs for the given footprint. The evolution to the stacked GAAFETs mitigates the patterning challenges by well-controlled epitaxy and high etching selectivity to achieve high performance and good electrostatics. The state-of-the-art stacked Si channel n/pGAAFETs and stacked Ge channel pGAAFETs have been reported. In this study, we demonstrate vertically stacked tensily strained GeSi nGAAFETs. The stacked GeSi nGAAFETs provide a possible solution to achieve high performance and to improve the electrostatics for Ge-based channel GAAFETs.The Ge/Ge0.85Si0.15 and Ge/Ge0.98Si0.02 multilayers are epitaxially grown on SOI substrates by CVD epitaxy. Ge buffer layers and sacrificial layers are not only used to achieve etching selectivity over GeSi layers to form the vertically stacked GeSi channels, but also used to provide tensile strain for GeSi n channels. Undoped channels and heavily doped sacrificial layers are used to reduce the impurity scattering and S/D resistance, respectively. The following PMA, laser annealing, and NiGe contacts formation for nFETs can further reduce the parasitic resistance to reveal the intrinsic merit of the high mobility GeSi channels.For GeSi nFETs, [Ge] larger than 85% in GeSi can ensure L valley conduction for small conductive effective mass to achieve high mobility. The △Ec between GeSi and Si is nearly zero and can be negligible. As a result, electron can flow through stacked GeSi channels and Si channel underneath for the nFETs. An engineering solution is provided to improve the electrostatic behaviors of Ge-based channels GAAFETs. We demonstrate the vertically stacked Ge0.85Si0.15 channels above a Si channel, which has good subthreshold behaviors. The VT difference between Ge0.85Si0.15 and Si can be tuned by the channel size optimizing. By narrowing the Ge0.85Si0.15 channel size to 5nm, the bandgap can be increased by quantum confinement and the short channel effect can be suppressed. As a result, more positive VT for Ge0.85Si0.15 than Si is observed. Therefore, the underneath Si channel with good electrostatic turn on first and dominate the subthreshold region. Good SS=76mV/dec and low DIBL=36mV/V are obtained due to low Dit and good short channel control. IOFF is also dramatically reduced and the ION/IOFF is improved to be 1.2E7 thanks to the increase of the bandgap and the improved short channel control for the narrow Ge0.85Si0.15 channels. The improved flicker noise of optimized channel size also indicates the enhanced reliability.To increase [Ge] in channel layers for mobility enhancement, Si incorporation as small as 2% into Ge can achieve sufficient etching selectivity of heavily phosphorus-doped Ge sacrificial layers over undoped Ge0.98Si0.02 to form two stacked Ge0.98Si0.02 nanowire channels, and introduce 0.27% uniaxial tensile strain for the electron mobility enhancement. The alloy scattering is still minimal for 2% Si. An additional 800oC anneal after the Ge buffer growth further improves the epi quality by confining misfit dislocations near the Ge buffer/Si interface. However, the Dit at Si underneath channel/dielectrics interface may be poor due to misfit dislocations confinement. As a result, the parasitic Ge/Si channel underneath the Ge0.98Si0.02 channels is completely removed by optimized etching. The distinct photoresponse of the floating channels and the parasitic channels can be a signature and provide a non-destructive method to check the existence of the parasitic channels. The photoresponse of the sole parasitic channel mainly shows the photocurrent (Iph), while the photoresponse of the sole floating channels without parasitic channel yields the negative threshold voltage shift (ΔVT) for nFETs. The device with both floating channels and the parasitic channel shows both photocurrent and negative threshold voltage shift under exposure. ION can be enhanced by scaled LG and large channel cross section. Record ION of 48μA per stack at VOV=VDS=0.5V and record Q (Gm,max/SSSAT) of 8.3 at VDS=0.5V with LG=40 nm are achieved among Ge nFETs.CVD grown Ge nGAAFET is compatible with Si technology. Excellent electrical characteristics are achieved and the results are comparable to mature Si nFETs. Indicating vertically stacked high mobility channel is promising candidate for CMOS applications in the future technology nodes to further extend the Moore’s law.Acknowledgements: This work is supported by MOST (MOST 109-2218-E-002-031- and 108-2622-8-002-016-) and MOE (NTU-CC-109L891601), Taiwan. The support from Taiwan Semiconductor Research Institute is also highly appreciated.

Optical Detection of Parasitic Channels of Vertically Stacked Ge0.98Si0.02 nGAAFETs

The distinct photoresponse of the floating channels and the parasitic channels can be a signature to check the existence of the parasitic channel. The photoresponse of the sole parasitic channel mainly shows the photocurrent ( ${I}_{\text {ph}}$ ), while the photoresponse of the sole floating channels without parasitic channel shows the negative threshold voltage shift ( $\Delta {V}_{\text {T}}$ ) for nFET. The device with both the floating channels and the parasitic channel shows both photocurrent and negative threshold voltage shift under exposure.

Nano-to-Microporous Networks via Inkjet Printing of ZnO Nanoparticles/Graphene Hybrid for Ultraviolet Photodetectors

Inkjet-printed photodetectors have gained enormous attention over the past decade. However, device performance is limited without postprocessing, such as annealing and UV exposure. In addition, it is difficult to manipulate the surface morphology of the printed film using an inkjet printer because of the limited options of low viscosity ink solutions. Here, we employ a concept involving the control of the inkjet-printed film morphology via modulation of cosolvent vapor pressure and surface tension for the creation of a high-performance ZnO-based photodetector on a flexible substrate. The solvent boiling point across different cosolvent systems is found to affect the film morphology, which results in not only distinct photoresponse time but also photodetectivity. ZnO-based photodetectors were printed using different solvents, which display a fast photoresponse in low-boiling point solvents because of the low carbon residue and larger photodetectivity in high-boiling point solvent systems due to the porous structure. The porous structure is obtained using both gas–liquid surface tension differences and solid–liquid surface differences, and the size of porosity is modulated from nanosize to microsize depending on the ratio between two solvents or two nanomaterials. Moreover, the conductive nature of graphene enhances the transport behavior of the photocarrier, which enables a high-performance photodetector with high photoresponsivity (7.5 × 102AW–1) and fast photoresponse (0.18 s) to be achieved without the use of high-boiling point solvents.

Epitaxial synthesis of ultrathin β-In2Se3/MoS2 heterostructures with high visible/near-infrared photoresponse.

van der Waals (vdWs) heterostructures, combining different two-dimensional (2D) layered materials with diverse properties, have been demonstrated to be a very promising platform to explore a new physical phenomenon and realize various potential applications in atomically thin electronic and optoelectronic devices. Here, we report the controlled growth of vertically stacked β-In2Se3/MoS2 vdWs heterostructures (despite the existence of large lattice mismatching ∼29%) through a typical two-step chemical vapor deposition (CVD) method. The crystal structure of the achieved heterostructures is characterized by transmission electron microscopy, where evident Moiré patterns are observed, indicating well-aligned lattice orientation. Strong photoluminescence quenching is obeserved in the heterostructure, revealing effective interlayer charge transfer at the interface. Electrical devices are further constructed based on the achieved heterostructures, which have a high on/off ratio and a typical rectifying behavior. Upon laser irradiation, the devices show excellent photosensing properties. A high responsivity of 4.47 A W-1 and a detectivity of 1.07 × 109 Jones are obtained under 450 nm laser illumination with a bias voltage of 1 V, which are much better than those of heterostructures grown via CVD. Most significantly, the detection range can be extended to near-infrared due to the relatively small bandgap nature of β-In2Se3. With 830 nm laser illumination, the devices also show distinct photoresponses with fast response speed even when operating at room temperature. The high-quality β-In2Se3/MoS2 heterostructures broaden the family of the 2D layered heterostructure system and should have significant potential applications in high-performance broadband photodetectors.

Different Infrared Responses From the Stacked Channels and Parasitic Channel of Stacked GeSn Channel Transistors

An optical non-destructive method to check the existence of the parasitic Ge0.94Si0.06 channel underneath vertically stacked Ge0.91 Sn0.09 channels by infrared illumination is investigated. The 1310-nm and 1550-nm infrared light excite the electron-hole pairs in both the stacked floating channels and parasitic channel. On the other hand, the 2000-nm infrared light generates photo-excited carriers in the floating GeSn channels, but not in the parasitic GeSi channel since the photon energy is lower than the bandgap of Ge0.94 Si0.06. The main infrared responses of the floating channels and parasitic channel are the threshold voltage shift and the photocurrent, respectively. In addition, the distinct photoresponses of the stacked channels and parasitic channel are further confirmed by transistors without floating channels. The mechanisms behind the infrared responses are proposed. The existence of the parasitic channel can be detected by the infrared response for the advanced technology nodes, where the presence of the parasitic channel is not desired for performance enhancement and power reduction.

A chain-type diamine strategy towards strongly anisotropic triiodide of DMEDA·I6

Linearly bonded triiodide chains with fairly small distance between the adjacent iodine ions feature a facile electron transfer and highly anisotropic properties. Here, we demonstrate a novel strategy towards a new one-dimensional linear triiodide DMEDA·I6, using chain-type N,N′-dimethyl-ethanediamine (DMEDA) cation to coordinate triiodine ions. This triiodide has the shortest distance between adjacent I3 and good linearity. An estimated electronic band gap of 1.36 eV indicates its semiconducting properties. 100 fold differences both in polarization-sensitive absorption and effective mass were achieved by simulation, with directions parallel and perpendicular to the a-axis of DMEDA·I6. The DME-DA·I6 single crystal-based photodetectors show a good switching characteristic and a distinct polarization-sensitive photoresponse with linear dichroic photodetection ratio of about 1.9. Strongly anisotropic features and semiconducting properties of DMEDA·I6 make this triiodide system an interesting candidate for polarization related applications.

Unveiling the Stimulated Robust Carrier Lifetime of Surface‐Bound Excitons and Their Photoresponse in InSe

AbstractIn contrast to zero‐bandgap metallic graphene, the binary semiconducting compound, InSe, possesses a tunable bandgap. Herein, a range of particle sizes of β‐InSe from bulk to few‐layer nanosheets and quantum dots are carefully prepared. The size‐dependent bandgap variation and photon‐induced carrier dynamics of InSe are systemically investigated. In contrast to the normal size‐dependent carrier lifetime trend observed at 700 nm, anomalous size‐independent carrier decay is observed at 500 nm. Through time‐dependent density functional theory calculations, the normal carrier lifetimes at lower probe photon energies are attributed to in‐plane excitons, whereas the abnormal size‐independent carrier lifetimes at higher probe photon energies are found to be stimulated by surface‐bound excitons. In view of the robust surface exciton, this suggests that InSe may possess an outstanding optoelectronic performance in the shorter wavelength range. Through photoelectrochemical detection experiments, it is confirmed that InSe features a high photocurrent density and stability and, in particular, a more distinct photoresponse at short wavelengths than at longer ones. Comprehending and quantifying the role of the surface‐bound excitons in InSe across a broad range of semiconductor nanostructures and their fundamental properties may play an important role in understanding the physical properties of 2D III–VI compound materials.

All-inorganic perovskite Cs4PbBr6 thin films in optoelectronic resistive switching memory devices with a logic application

Perovskite-based Cs4PbBr6 has potential applications in optoelectronic devices, such as photodetectors, electroluminescence devices and color converters. All-inorganic perovskite Cs4PbBr6 thin films were successfully prepared by a simple low-temperature synthesis method and were first implemented as an insulating layer in Au/Cs4PbBr6/PEDOT:PSS/Pt devices. The memory devices possess reproducible bipolar resistive switching behavior, low operating voltages, good endurance, and long retention times. Furthermore, the novel sandwich architecture enables the application of the Cs4PbBr6 films as memristors and photoresponsive behaviors. Considering the distinct photoresponses of the resistance state as a nonvolatile memory, the devices can be used as a logical "OR" gate by applying bias voltages and light illumination as input signals. The formation and annihilation of Br- ion vacancy filaments induced by the external bias and light illumination can result in pronounced resistive switching performance. It is believed that solution-processed Cs4PbBr6-based devices have great potential for technological deployment at the forefront as a photonic nonvolatile memory as well as integrated modulating and arithmetic functions.

Electrical and Optoelectronic Properties of Chemically Prepared PbS/MnS Heterojunction

Lead sulfide (PbS)/manganese sulfide (MnS) heterojunction is synthesized by a simple two-step chemical bath deposition technique. The as-synthesized heterojunction is studied based on the optical and electrical analyses. The optical absorbance spectrum of the test structure confirms dual peaks at two different wavelengths, which has prompted consideration of the two band gaps of the structure. The origin of dual peaks in the absorbance plot is attributed to the existence of the PbS base layer and the MnS window layer. The band gaps are estimated using the conventional Tauc’s method (Eg = 1.75 eV and 2.9 eV) and also by the absorbance spectrum fitting method (Eg = 1.82 eV and 2.97 eV). In the dc analyses, the PbS/MnS heterojunction possesses low dark current and high dynamic resistance. However, under illumination (400–700 nm) a distinct photo-response is observed, showing a substantial rise in device current with the reduction of dynamic resistance. The photo-response of the heterojunction is examined at 635–699 nm, 514–538 nm and 410–452 nm wavelengths by analyzing the photo-current and photo-resistance. The device is found to be more photosensitive at lower wavelength illuminations compared to the higher wavelength exposures.

Silicon/Perovskite Core-Shell Heterojunctions with Light-Trapping Effect for Sensitive Self-Driven Near-Infrared Photodetectors.

In this article, we fabricated a sensitive near-infrared (NIR) light detector by directly coating a layer of Cs-doped FAPbI3 perovskite film onto vertical Si nanowire (SiNW) array. The as-assembled SiNW array/perovskite core-shell heterojunction exhibits a typical rectifying characteristic in darkness and distinct photoresponse characteristics under light illumination. Owning to the remarkable photovoltaic effect, the heterojunction can work as a self-driven NIR detector without an exterior energy supply. Further photoresponse investigation reveals that the photodetector is sensitive in a wide wavelength range with maximum sensitivity at ∼850 nm. The responsivity ( R) and specific detectivity ( D*) are estimated to be 14.86 mA W-1 and 2.04 × 1010 Jones at 0 Vbias, respectively, which can be improved to 844.33 mA W-1 and 3.2 × 1011 Jones at a bias voltage of -0.9 V. In addition, the present device also possesses distinct advantages of a large Ilight/ Idark ratio exceeding 104, swift response rate with rise/decay times of 4/8 μs, and relatively good ambient stability. According to our numerical simulation based on finite element method, the superior device performance is associated with strong light-trapping effect in such unique core-shell heterojunction array.

Fabrication of cerium-doped β-Ga2O3 epitaxial thin films and deep ultraviolet photodetectors.

High-quality cerium-doped β-Ga2O3 (Ga2O3:Ce) thin films could be achieved on (0001)α-Al2O3 substrates using a pulsed-laser deposition method. The impact of dopant contents concentration on crystal structure, optical absorption, photoluminescence, and photoelectric properties has been intensively studied. X-ray diffraction analysis results have shown that Ga2O3:Ce films are highly (2¯01) oriented, and the lattice spacing of the (4¯02) planes is sensitive to the Ce doping level. The prepared Ga2O3:Ce films show a sharp absorption edge at about 250nm, meaning a high transparency to deep ultraviolet (DUV) light. The photoluminescence results revealed that the emissions were in the violet-blue-green region, which are associated with the donor-acceptor transitions with the Ce3+ and oxygen vacancies related defects. A simple DUV photodetector device with a metal-semiconductor-metal structure has also been fabricated based on Ga2O3:Ce thin film. A distinct DUV photoresponse was obtained, suggesting a potential application in DUV photodetector devices.

Distinct photoresponse in graphene induced by laser irradiation

The graphene-based photodetector with tunable p-p+-p junctions was fabricated through a simple laser irradiation process. Distinct photoresponse was observed at the graphene (G)-laser irradiated graphene (LIG) junction by scanning photocurrent measurements, and its magnitude can be modulated as a result of a positive correlation between the photocurrent and doping concentration in LIG region. Detailed investigation suggests that the photo-thermoelectric effect, instead of the photovoltaic effect, dominates the photocurrent generation at the G-LIG junctions. Such a simple and low-cost technique offers an alternative way for the fabrication of graphene-based optoelectronic devices.

Improved photovoltaic performance of multiple carbon-doped ZnO nanostructures under UV and visible light irradiation.

We report synthesis of multiple carbon-doped ZnO nanostructures by using carbon cloth as substrates to obtain multiple hollow ZnO microtube-nanowire structures. X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy analysis clearly show that carbon is doped into ZnO through substitution of carbon for oxygen in the growth and annealing processes. Upon exposure to 633-nm red laser, a distinct photoresponse can be observed, which indicates that carbon doping in ZnO can well extend its light harvesting to visible light region. Furthermore, a prototype of photovoltaic cell was fabricated to demonstrate the photovoltaic performance of multiple carbon-doped ZnO nanostructures under UV and visible light irradiation. This result shows that carbon-doped ZnO can act as effective photoactive materials for photoelectric components.

Quantum dot quantum cascade infrared photodetector

We demonstrate an InAs quantum dot quantum cascade infrared photodetector operating at room temperature with a peak detection wavelength of 4.3 μm. The detector shows sensitive photoresponse for normal-incidence light, which is attributed to an intraband transition of the quantum dots and the following transfer of excited electrons on a cascade of quantum levels. The InAs quantum dots for the infrared absorption were formed by making use of self-assembled quantum dots in the Stranski–Krastanov growth mode and two-step strain-compensation design based on InAs/GaAs/InGaAs/InAlAs heterostructure, while the following extraction quantum stairs formed by LO-phonon energy are based on a strain-compensated InGaAs/InAlAs chirped superlattice. Johnson noise limited detectivities of 3.64 × 1011 and 4.83 × 106 Jones at zero bias were obtained at 80 K and room temperature, respectively. Due to the low dark current and distinct photoresponse up to room temperature, this device can form high temperature imaging.