Photodetector Structure Research Articles

A vertical structure photodetector based on all‐inorganic perovskite quantum dots

AbstractIn this work, the vertical structure photodetector based on CsPbBr3 quantum dots (QDs) with a structure of indium tin oxide (ITO)/zinc oxide (ZnO)/CsPbBr3 QDs/Au is reported. In this device, CsPbBr3 QDs film works as the light‐harvesting layer, and ZnO QDs film acts as the electron transport channel, which can extract the electron efficiently and improve the quality of CsPbBr3 QDs film. As a result, the on/off ratio, detectivity and rise time (decay time) of CsPbBr3/ZnO hybrid photodetector are measured to be 2.4 × 106, 2.25 × 1011, and 62 milliseconds (82 ms) under 0‐V bias. This work inspires the development of vertical structure photodetectors based on the all‐inorganic perovskite QDs.

Enhanced Photoresponsivity of a GaAs Nanowire Metal-Semiconductor-Metal Photodetector by Adjusting the Fermi Level.

Metal-semiconductor-metal (MSM)-structured GaAs-based nanowire photodetectors have been widely reported because they are promising as an alternative for high-performance devices. Owing to the Schottky built-in electric fields in the MSM structure photodetectors, enhancements in photoresponsivity can be realized. Thus, strengthening the built-in electric field is an efficacious way to make the detection capability better. In this study, we fabricate a single GaAs nanowire MSM photodetector with superior performance by doping-adjusting the Fermi level to strengthen the built-in electric field. An outstanding responsivity of 1175 A/W is obtained. This is two orders of magnitude better than the responsivity of the undoped sample. Scanning photocurrent mappings and simulations are performed to confirm that the enhancement in responsivity is because of the increase in the hole Schottky built-in electric field, which can separate and collect the photogenerated carriers more effectively. The eloquent evidence clearly proves that doping-adjusting the Fermi level has great potential applications in high-performance GaAs nanowire photodetectors and other functional photodetectors.

Ultrahighly Photosensitive and Highly Stretchable Rippled Structure Photodetectors Based on Perovskite Nanocrystals and Graphene

Stretchable optoelectronic devices are the need of the hour when it comes to making present day technologies user-friendly. These devices when placed conformably on the human skin or any other artificial intelligence products must function in all their capacities to get a durable and highly sensitive device performance. Stretchable photodetectors are the core fundamental constituents that fall under the umbrella of flexible optoelectronic devices. Although a significant amount of research has been reported on stretchable photodetectors, good performance still remains a challenge. Nanometer-sized methylammonium lead bromide ((MA)PbBr3) perovskite nanocrystals can significantly emit and absorb light in the visible spectrum. With high quantum yield and stable optical and electronic properties, when they are subjected to mechanically tunable two-dimensional (2D) composites, we obtain better performance from stretchable optoelectronic devices. Here, a hybrid photodetector composed of perovskite nanocrystals and graphene of rippled geometry is demonstrated, where a thin film of photon-absorbing perovskite nanocrystals is placed on rippled graphene that contributes to a photoresponsivity on the order of ∼6 × 105 A W–1. The large photoresponsivity value places this hybrid stretchable device in the highest position among devices with similar functionality. It is found that the photoresponsivity of the perovskite nanocrystals and graphene hybrid rippled structure photodetector is strain tunable with a stretchability up to 100%. In addition, the hybrid rippled structure photodetector has wearability and durability. All of these superior functionalities lead the way toward fabricating stretchable optoelectronic devices suitable for applications in the fields of biomedicine, defense systems, fire detection, and flexible display panels.

Upmost efficiency, few-micron-sized midwave infrared HgCdTe photodetectors.

Resonant cavity-assisted enhancement of optical absorption was a photodetector designing concept emerging about two and half decades ago that responded to the challenge of thinning the photoactive layer while outperforming the efficiency of the monolithic photodetector. However, for many relevant materials, meeting that challenge with such a design unrealistically requires many layer deposition steps, so that the efficiency at goal hardly becomes attainable because of inevitable fabrication faults. Under this circumstance, we suggest a new approach for designing photodetectors with an absorber layer as thin as those in respective resonant cavity-enhanced ones, but concurrently, the overall detector thickness would be much thinner and top-performing. The proposed structures also contain the cavity-absorber arrangement but enclose the cavity by two dielectric one-dimensional grating-on-layer structures with the same grating pitch, instead of the distributed Bragg reflectors typical of the resonant cavity enhancement approach. By a design based on in-house software, the theoretical feasibility of such ∼7.0-8.5 μm thick structures with ∼100% efficiency for a linearly polarized (TE or TM) mid-infrared range radiation is demonstrated. Moreover, the tolerances of the designed structures' performance against the gratings' fabrication errors are tested, and fair manufacturing tolerance while still maintaining high peak efficiency along with a small deviation of its spectral position off initially predefined central-design wavelength is proved. In addition, the electromagnetic fields amplitudes and Poynting vector over the cavity-absorber area are visualized. As a result, it is inferred that the electromagnetic fields' confinement in the designed structure, which is a key to their upmost efficiency, is two-dimensional, combining in-depth vertical resonant-cavity-like confinement with the lateral microcavity like one set by the presence of gratings.

Direct MBE growth of metamorphic nBn infrared photodetectors on 150 mm Ge-Si substrates for heterogeneous integration

GaSb-based infrared (IR) photodetector structures were grown on large diameter, 150 mm, Si substrates using a multistep metamorphic buffer architecture process. A standard bulk InAsSb/AlAsSb barrier detector design with a cutoff wavelength of ∼4 μm was used as a test vehicle for this growth process. First, a Ge layer was deposited by chemical vapor deposition, creating a Ge-Si substrate for the subsequent molecular beam epitaxy growth of the remaining III–V buffer and device layers. X-ray diffraction and photoluminescence measurements demonstrated high crystal quality and excellent cross-wafer uniformity of the device epiwafer characteristics. Microscopy evaluation revealed a moundlike surface morphology with a low root-mean-square roughness value below 2 nm, suitable for focal plane array (FPA) fabrication. Large-area mesa diode test devices measured dark currents of 5 × 10−5 A/cm2 and a quantum efficiency of 60% for the Sb-detector grown on Ge–Si. The same structure was fully fabricated into a standard FPA and produced good imagery resolution with high operability. These excellent results for this first FPA manufactured from an Sb-photodetector grown on Si using this Ge-Si architecture demonstrate a promising path in the progression of Sb-IR technology as it transitions from development to next-generation, large-format IR manufacturing with an eye toward potential heterogeneous integration with silicon.

Defect Characterization of InAs/InGaAs Quantum Dot p-i-n Photodetector Grown on GaAs-on-V-Grooved-Si Substrate

The performance of semiconductor devices on silicon can be severely degraded by the presence of dislocations incurred during heteroepitaxial growth. Here, the physics of the defect mechanisms, characterization of epitaxial structures, and device properties of waveguide photodetectors (PDs) epitaxially grown on (001) Si are presented. A special GaAs-on-V-grooved-Si template was prepared by combining the aspect ratio trapping effects, superlattice cyclic, and strain-balancing layer stacks. A high quality of buffer structure was characterized by atomic force microscopy (AFM) and electron channeling contrast imaging (ECCI) results. An ultralow dark current density of 3.5 × 10–7A/cm2 at 300 K was measured under −1 V. That is 40× smaller than the best reported value of epitaxially grown InAs/GaAs quantum dot photodetector structure on GaP/Si substrate. Low frequency noise spectroscopy was used to characterize the generation and recombination related deep levels. A trap with an activation energy of 0.4 eV was id...

Monolithically grown 2.5 μm InGaAs photodetector structures on GaP and GaP/Si (001) substrates

This work reports on the demonstration and investigation of short-wave infrared In0.83Ga0.17As photodetectors with cutoff wavelength of 2.5 μm monolithically grown on GaP and GaP/Si (001) substrates. The lattice mismatch of the photodetector structure is about +10% to the substrates and the photodetector layers are fully relaxed from x-ray diffraction measurement. Distinct photoluminescence spectra are observed even at room temperature. The resistance area product is 10.4 and 9.3 Ωcm2, and 2.0 μm responsivity is 0.49 and 0.41 A W−1 at 300 K for the devices on GaP and GaP/Si substrates, respectively. The 300 K peak detectivity at 2.0 μm of about 1.2 × 1010 and 1.0 × 1010 cmHz1/2 W−1 have been achieved for the two photodetectors.

Studies on coupling of optical power to graphene based nano waveguide at 1550 nm for application in photonic integrated circuit

Present research deals with lucid analysis on waveguide and photodetector structure for realising efficient photonics integrated circuit at wavelength of 1550 nm. The proposed structure comprises of Raman laser as optical source, waveguide as channel and p-i-n photodiode as photodetector, where Raman lasing source is designed using silicon semiconductor material and the waveguide as well as intrinsic region of p-i-n photodetector is envisaged by using graphene. Further, plane wave expansion (PWE) method is employed to obtain reflectance and absorbance of the proposed graphene based waveguide. Again, the principle of numerical investigation of coupling efficiency between laser to waveguide as well as waveguide to photodetector is based on overlap integral method which is carried out by overlapping of their mode field profiles. Moreover, 3 dB misalignment effect is analysed which is found to be 1.2 μm, 2.2 μm and 1.6 μm for vertical offset, horizontal offset and angular offset respectively in laser to waveguide coupling process. Further, coupling efficiency between waveguide and photodetector is investigated where, computational mechanisms infers that graphene based photodetector delivers a responsivity of 1.1 Amp/watt and negligible dark current of 72 pA, which is apt for realising high coupling efficiency. Eventually, the outcome of present research asserted that overall transmitted efficiency of 94.86% can be accomplished for the proposed structure at the aforesaid wavelength which came up as a good candidate for future photonics integrated circuits.

Organolead halide perovskite-based metal-oxide-semiconductor structure photodetectors achieving ultrahigh detectivity

Organolead halide perovskite with excellent optoelectronic properties, which endows its potential applications in versatile optoelectronic device including solar cells and photodetectors. In spite of great efforts made on the perovskite photodetectors, novel device configurations based on perovskite films have to be explored to further improve the performance. Here, we present perovskite photodetectors enabled by a novel metal (Al)–oxide–semiconductor (perovskite) (MOS) structure. The unique photodetector can work on a wide voltage range and exhibits extreme characteristics with a pA-scale dark current, and a high detectivity (>1014 Jones). Both ultralow dark and light currents enable the small power consumption output ∼nW under 2 mW cm−2 at 2 V. The C–V data analysis proves that the charge carriers are accumulated at the oxide/perovskite interface, which leads to the reduction of the conduct band offset. At a low voltage the current transport behaviors for the MOS structure photodetectors are dominated by the Ohm’s Law, while at a high voltage, the main mechanism is Schottky emission which is demonstrated by temperature-dependence I–V measurements. Our results strongly propose the use of perovskite based photodetectors with a unique MOS structure in the application of optoelectronic devices.

Nano-scale planar photodetector based on ring form MQWs for FIR regime

In this paper, we proposed a new design of infrared photodetector structure based on ring-shaped multiple quantum wells for long-infrared and far-infrared (FIR) regimes. The absorption coefficient of the proposed photodetector that consists of GaAs/Al0.25Ga0.75As quantum wells with a thickness of 4 nm and a barrier of 40 nm has been calculated, from which a dominant peak of 50 um locates in the FIR regime. The proposed device has a planar structure with small thickness compared with ordinary rectangular multiple quantum well photodetectors. Also, there is 100% enhancement in typical IR absorption versus these ordinary photodetectors. Electronic states and wave functions calculated through solving the Schrodinger equation and then the effect of quantum well number on important parameters of photodetectors, such as gain mode and dark current, are investigated. According to the results, dark current decreases 1 order of magnitude when the number of quantum wells increases from 3 to 4. Also, absorption has redshift and simultaneously increases.

Narrow-Band 4.3<italic>μ</italic>m Plasmonic Schottky-Barrier Photodetector for CO2 Sensing

Using an embedded platinum silicide (PtSi) grating, a Schottky-barrier photodetector structure for narrow-band detection of mid-infrared (mid-IR) radiation is proposed and designed. Schottky-barrier photodetectors designed for the infrared wavelengths suffer from poor efficiency and photoresponse. We propose a photodetector based on PtSi-Si Schottky junction with increased interface area where hot carriers are more likely to cross the junction in favor of a higher photoresponse. Furthermore, a guided-mode resonance of the presented periodic structure is coupled to its Fabry–Perot resonance to achieve narrow-band absorption. The proposed photodetector absorbs 84% of incident power at a wavelength of 4.3 μm with a full-width half-maximum bandwidth of 94 nm. High photoresponsivity and compatibility with complementary metal oxide semiconductor process render the proposed structure a low-cost photodetector in the mid-IR range for CO2 sensing.

Influence of twin boundaries on the photocurrent decay of nanobranch and dense-forest structured SnO2 UV photodetectors

The nanobranch (Nb) and dense-forest (DF) structured tin dioxide thin films were prepared by hot wall nebulizer spray pyrolysis technique for different precursor concentrations. The structural, optical and morphological properties were studied by X-Ray diffraction, UV–visible spectrophotometer, Photoluminescence spectrophotometer and Field emission scanning electron microscopy. The growth mechanism of Nb and DF structure formation were discussed. The performance of UV Photodetector is studied under UV light of 365 nm wavelength and low bias voltage of 0.4 mV. The parameters of PDs such as responsivity, external quantum efficiency, linear dynamic response, detectivity and photosensitivity were calculated. The SnO2 Nbs and DF structure PDs show significant performance at low light intensity (0.2 mW/cm2) and low bias voltage (0.4 mV). Influence of twin boundary on the slow decay of photocurrent is studied with exponential fitting. The relationship between depletion layer, dark current and photosensitivity is studied with surface adsorbing oxygen ions (O2−).

In Situ Fabrication of 2D WS2/Si Type-II Heterojunction for Self-Powered Broadband Photodetector with Response up to Mid-Infrared

The high-performance broadband photodetectors have attracted intensive scientific interests due to their potential applications in optoelectronic systems. Despite great achievements in two-dimensional (2D) materials based photodetectors such as graphene and black phosphorus, obvious disadvantages such as low optical absorbance and instability preclude their usage for the broadband photodetectors with the desired performance. An alternative approach is to find promising 2D materials and fabricate heterojunction structures for multifunctional hybrid photodetectors. In this work, 2D WS2/Si heterojunction with a type-II band alignment is formed in situ. This heterojunction device produced a high Ion/Ioff ratio over 10,6 responsivity of 224 mA/W, specific detectivity of 1.5 × 1012 Jones, high polarization sensitivity, and broadband response up to 3043 nm. Furthermore, a 4 × 4 device array of WS2/Si heterojunction device is demonstrated with high stability and reproducibility. These results suggest that the WS2...

Amorphous MgInO Ultraviolet Solar-Blind Photodetectors

The magnesium oxide is one of the promising candidate's materials that can act as solar blind photodetectors. However, the intrinsically low thermal conductivity of MgO, which is restrict the application in electric device. The magnesium oxide exhibits the poor conductivity which could improved by doing method. This paper fabricated magnesium indium oxide (MgInO) solar-blind photodetectors by doping indium oxide with magnesium oxide through co-sputtering deposition method. The photodetector comprises a bottom glass substrate, an MgInO thin film, and an interdigitated gold electrode to complete the metal-semiconductor-metal structure of the solar-blind photodetector. The experimental results indicate that the photo-to-dark-current ratio is 1.4 × 10 4 , and the responsivity is 1.47 A/W when a reverse bias voltage of 2 V is applied. Furthermore, the noise equivalent power and detectivity are 7.77×10 -11 W and 1.75×10 11 cm H 0.5 W -1 with a 2 V bias voltage, respectively.

Optimization of in-device depleted passivation layer for InGaAs photodetectors

Lattice matched InGaAs/InP photodetector structure with an InP layer for in-device passivation purposes has been analyzed numerically, an optimized design for mesa type devices has been proposed and experimental verification has been shown. Structural and electrical parameters such as thickness and doping concentration of InP layer have been studied in order to avoid any hole barrier possible in the valence band and to achieve a high photo-current with pixel isolation while reducing the surface leakage dark current component substantially. The passivation effect has been quantified for a variety of surface instability levels in comparison with the traditional InGaAs/InP hetero-junction structure and fully depleted InP layer has shown to be able to isolate pixels successfully and provide passivation that can help reduce the total dark current more than one order of magnitude. Photo-response in the proposed structure has been observed to be enhanced as well due to the increased collection efficiency.

Three-Dimensional Topological Insulator Bi2Te3/Organic Thin Film Heterojunction Photodetector with Fast and Wideband Response from 450 to 3500 Nanometers.

In the pursuit of broadband photodetection materials from visible to mid-IR region, the fresh three-dimensional topological insulators (3D TIs) are theoretically predicted to be a promising candidate due to its Dirac-like stable surface state and high absorption rate. In this work, a self-powered inorganic/organic heterojunction photodetector based on n-type 3D TIs Bi2Te3 combined with p-type pentacene thin film was designed and fabricated. Surprisingly, it was found that the Bi2Te3/pentacene heterojunction photodetector exhibited a fast and wideband response from 450 to 3500 nm. The optimized responsivity of photodetector reached 14.89 A/W, along with the fast response time of 1.89 ms and the ultrahigh external quantum efficiency of 2840%. Moreover, at the mid-IR 3500 nm, our devices demonstrated a responsivity of 1.55 AW-1, which was several orders of magnitude higher than that of previous 3D TIs photodetector. These excellent properties indicate that the inorganic/organic heterojunction, that is, the combination of 3D TIs with organic materials, is an exciting structure for high performance photodetectors in the wideband detection region. On account of the fact that the device is constructed on mica substrate, this work also represents a potential scenario for flexible optoelectronic devices.

The Effects of Mg Contents on Mg<italic>x</italic>Zn1−xO-Based Metal-Semiconductor-Metal Ultraviolet Photodetectors by Ultrasonic Spray Pyrolysis Deposition

The Mg <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Zn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</sub> O thin films with Mg/Zn mole fraction of 0.1/0.9, 0.2/0.8, and 0.3/0.7 were deposited by the ultrasonic spray pyrolysis deposition method. The X-ray diffraction, X-ray photoelectron spectroscopy, and Raman were used to analyze the material characteristics, including crystal structures, crystal orientations, chemical qualitative, and quantitative characteristics. The photoluminescence spectrum was used to observe the near-band-edge emission and trap energy level. The refractive index and extinction coefficient of the Mg <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Zn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</sub> O thin films were measured by the ellipsometer. The metal-semiconductor-metal structure photodetectors were fabricated. The electrical characteristics, including current-voltage and Schottky barrier height characteristics were investigated. The photoresponse showed that the Mg <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.1</sub> Zn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.9</sub> O-based photodetector had the highest photoresponsivity and the Mg <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.3</sub> Zn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.7</sub> O-based photodetector had the shortest response time and the highest detectivity. Further, the contents of Mg in the Mg <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Zn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</sub> O affected the cutoff wavelength of the photodetector.

A novel dual-color total internal reflection fluorescence detecting platform using compact optical structure and silicon-based photodetector

A novel dual-color total internal reflection fluorescence detecting platform (DTP) was developed for the simultaneous detection of two fluorescence dyes. The DTP employed a simple and compact optical system and a Si-based photodetector SOP-1000 assembly to improve the optical efficiency and detection sensitivity. In the optical system, a single-multimode fiber optic coupler was applied for the transmission of two wavelength excitation lights and the collection and transmission of two wavelength fluorescence signals, and a fiber optical switch controlled two wavelength excited lights to alternatively enter into the combined tapered fiber optic probe and two wavelength fluorescence dyes were alternatively excited. The simultaneous and sensitive detection of two wavelength fluorescence signals was achieved by one photodetector SOP-1000 based on the time-resolved effect of the fiber optical switch. The DTP demonstrated its sensitivity of 50 fW light intensity, and the limit of detection of Cy5.5 and Pacific Blue dye (PB) were 0.05 nM and 2.1 nM, respectively. This miniaturized and integrated DTP with high sensitivity, simple optical structure, negligible cross-talk, and cost-effectiveness could be a potential alternative to the conventional dual-color fluorescence detecting systems. It could also be a powerful component of a μ-TAS system for highly sensitive dual-color fluorescence detection.

Au@HgxCd1-xTe core@shell nanorods by sequential aqueous cation exchange for near-infrared photodetectors

We have explored the synthesis of Au@HgxCd1-xTe core@shell nanorods by sequential aqueous cation exchange (ACE) for near-infrared photodetector application. A number of related Au@telluride core/shell nanorod structures were put forwarded, taking advantage of multi-step transformations through a binary and then a ternary phase for the telluride shells. The latter have a high degree of crystallinity thanks to the step-wise ACE method. The use of only trace amounts of Cd2+ coordinated with tri-n-butylphosphine, assisted the phase transformation from an amorphous Ag2Te shell to a highly crystalline Ag3AuTe2 shell in the first stage; this was followed by a further cation exchange (CE) step with far higher Cd2+ levels to fabricate a highly crystalline CdTe shell, and with an additional CE with Hg2+ to convert it to a HgxCd1-xTe shell. The composition of the shell components and the well-controlled thickness of the shells enabled tunable surface plasmon resonance properties of the Au@telluride nanorods in the NIR region. Utilizing the enhanced NIR absorption, a hybrid photodetector structure of Au@HgxCd1-xTe nanorods on graphene was fabricated, showing visible to NIR (vis-NIR) broadband detection with high photoresponsivity (~106 A/W).

Interface regulation and photoelectric performance of CdZnTe/AlN composite structure for UV photodetector

AlN ceramic substrates (c-AlN), with excellent thermal conductivity, were used to deposit high-quality polycrystalline CdZnTe (CZT) thick films for the first time. Meanwhile, AlN transition layers, made by magnetron sputtering method, have been introduced and annealed to modulate the interface properties of CZT/c-AlN composite structures for UV photodetectors. The relationship between the structure as well as performance of CZT films and the anneal temperature of AlN transition layers was studied by SEM, XRD, EDS, UV–vis spectra, XPS and current–voltage (I-V) characteristic. The CZT films deposited on the AlN transition layer annealed at 1200 °C have the best properties, with the full width at half maximum (FWHM) and leakage current of 0.163°and 2.15 × 10−9 A, respectively. The interface regulation can effectively promote the crystallinity of CZT films and lead to optimum UV detection performance of CZT/AlN composite structures.