Fabrication Of Photodetectors Research Articles

Enhanced Visible-Light Photodetection with Undoped and Doped ZnO Thin-Film Self-Powered Photodetectors.

Photodetection plays an essential role in the visible-light zone and is important in modern science and technology owing to its potential applications in various fields. Fabrication of a stable photodetector remains a challenge for researchers. We demonstrated a high-response/recovery and self-powered undoped ZnO (UZO) and Cu-doped ZnO (CZO) thin film-based visible-light photodetector fabricated on a cost-effective Si substrate using reactive cosputtering. The structural, morphological, and optical properties of CZO and UZO thin films have been examined using X-ray diffraction, field emission scanning electron microscopy, X-ray photoelectron spectroscopy, atomic force microscopy, and photoluminescence spectroscopy. The results of the CZO/n-Si photodetector compared with those of the undoped ZnO (UZO)/n-Si photodetector show that the CZO/n-Si exhibits a higher on/off ratio, responsivity, and detectivity than UZO/n-Si. Also, the CZO/n-Si photodetector shows high stability and reproducibility over 20 cycles after 180 days. A relative study of CZO/n-Si- and UZO/n-Si-based photodetectors reveals the enhanced performance of the CZO/n-Si photodetector, which has a high on/off ratio of ∼300 with a high specific detectivity of 2.8 × 1010 Jones for 75 mW visible light. The prepared self-powered CZO/n-Si/Ag thin film-based visible-light photodetector paves the way for the development of high-performance photodetector designs.

Study of I-V and photoelectronic properties of self-biased p-GeSe/n-Hf0.05Sn0.95Se2 heterostructure

Two-dimensional/two-dimensional (2D/2D) heterojunctions are one of the most adaptable technological methods for the fabrication of photodetectors due to their novel properties. In this paper, we present the fabrication of a p-GeSe/n-Hf0.05Sn0.95Se2 heterostructure by depositing GeSe via the thermal evaporation technique on Hf0.05Sn0.95Se2 crystal. The surface morphology is investigated by scanning electron microscopy. The structural characteristic is studied by X-ray diffraction technique. The heterostructure is characterized by studying the I-V characteristics recorded with the aid of a Keithley 4200 SCU under dark and illuminated conditions. The illumination was varied w.r.t. incident intensity and wavelength, and the lowest ideality factor (3.15) was achieved under blue light illumination with an intensity of 120 mW/cm2. The photoresponse characteristics of this heterojunction are also studied under different illuminations at zero bias voltage and at room temperature. The highest photocurrent of 113.09 μA is obtained under blue light with 120 mW/cm2 intensity.

Laminated Polymer‐Encapsulated Halide Perovskite Photoconductors

AbstractHerein, a simple, solvent‐free method to fabricate polymer‐encapsulated halide perovskite photoconductors is described. Dry mechanochemical synthesis is used to prepare CsPbBr3 in the presence of poly(butyl methacrylate) (PBMA). The resulting composite powder is then heated and pressed into a free‐standing disk with a thickness controlled by a metallic spacer ring. The disk can be laminated on a glass substrate patterned with interdigitated electrodes, resulting in a planar photoconductor device. The best photoconductive performance is obtained for disks that consist of 75 wt.% CsPbBr3 in PBMA, reaching a detectivity of ≈2 × 1011 Jones. Moreover, by adjusting the thickness of the disk, narrowband detectors can be obtained due to charge collection narrowing. Depending on the thickness of the pressed disk, the position and width of the detectivity peak can be tuned. At last, the disks are tested as possible absorber materials for X‐ray detectors, where ow detection limit, and fast and linear response are measured for perovskite‐polymer disks with 50 wt.% perovskite content. This work shows a simple and versatile approach toward the fabrication of halide perovskite photodetectors, which can be carried out in air and without the use of solvents.

Asymmetric Schottky contacts induced via localized ultrafast laser irradiation for ultrasensitive, self-powered, 2D photodetectors

Self-powered photodetectors hold great promise for addressing power-related challenges in the “Internet of Things (IoT)” era. However, the self-powered performances of a metal-semiconductor-metal (MSM) structure photodetector are inherently limited due to the presence of the symmetric Schottky contacts, leading to canceling photocurrents in opposite directions, while constructing an asymmetric MSM structure demands complicated design or sustained external fields. Herein, we propose a novel contact engineering strategy based on localized femtosecond (fs) laser irradiation, achieving an asymmetric band structure in an MSM-structure photodetector with pristine symmetric Schottky contacts. As a result, a MoS2 photodetector that exhibits exceptional photoresponse and self-powered performances is successfully fabricated. The device type transitions from a photoconductor to a photodiode, exhibiting a significant improvement in the rectification ratio from 1 to > 104. A comprehensive study on fs laser-based contact engineering is conducted by investigating atom diffusion, element variation, and Schottky barrier height variation. Notably, the photodetector demonstrates an exceptional zero-bias responsivity of 1.72 A/W, with a short circuit current of 37.2 nA and maximum output electric power of 1.67 nW. Our work provides a new strategy for modifying the energy band structure and facilitates the fabrication of high-performance self-powered photodetectors.

Photoswitching effect of graphene photogated diodes with interfacial layers

Graphene/semiconductor heterojunction-based photodetectors are expected to achieve high performance in various wavelength regions. Graphene photogated diodes (GPDs) based on such heterojunctions are promising for the fabrication of high-performance photodetectors, which cannot be achieved using conventional technologies. However, their action mechanism has not yet been theoretically demonstrated. In this study, we investigated the mechanism of GPDs with and without an interfacial layer. We demonstrated that the thin interfacial native oxide layer is responsible for the reduction in the Fermi level induced by photogating, which is similar to “photoswitching.” This effect induces an extraordinarily large output current in GPDs with a barrier layer.

Impact of controlling the barrier height on fabrication of high performance β-Ga2O3 solar-blind photodetectors

Impact of controlling the barrier height on fabrication of high performance β-Ga2O3 solar-blind photodetectors

High-Performance Self-Driven SnSe/Si Heterojunction Photovoltaic Photodetector

Tin monoselenide (SnSe), which belongs to group IV–VI monochalcogenides, has obtained significant attention in the field of photodetection owing to its ultrahigh carrier mobilities. However, the great challenges of preparing high-quality films and high-performance devices still need to be conquered. Herein, high-density continuous SnSe films were deposited on a Si substrate using magnetron sputtering technology, and a self-driven photovoltaic-type broadband photodetector from the visible light range (VIS) to the near-infrared (NIR) range based on SnSe/Si heterojunction was constructed. Owing to its high carrier mobility, narrow band gap structure, and strong internal electric field, the SnSe/Si heterojunction device exhibits an ultrafast response and high responsivity (R), which achieves a wide spectral response of 405–980 nm. Under zero bias voltage, the greatest R and detectivity (D*) of the heterojunction were 704.6 mA/W and 3.36 × 1011 Jones at 405 nm. Furthermore, the device had a fast response time (rise time) of 20.4 μs at 980 nm of illumination. This work provides a new strategy for the fabrication of high-performance, low-cost, and self-driven photodetectors.

Improved performance and stability in CH3NH3PbI3/Si heterojunction photodetectors realized by ZIF-67 additive assisted Co ion doping

Lead halide perovskites have been regarded as promising materials for fabrication of high-performance photodetectors (PDs). However, spin-coated perovskite thin films generally have suffered from high-density grain boundaries and defect states, which severely deteriorated the performance and stability of resulting PDs. Fortunately, the above issues can be effectively solved via additive assisted metal ions doping. In this work, Co-based zeolite imidazole framework (ZIF-67) additive assisted Co ion doping has been proposed to prepare high-quality perovskite CH3NH3PbI3 (MAPbI3) thin films. Morphological, structural, optical, and electrical studies have shown that Co ion doping decreased grain boundaries as well as suppressed defect states, which greatly enhanced the performance and stability of MAPbI3/Si heterojunction PDs, including reducing dark current, increasing photocurrent, and increasing response speed. Finally, the mechanisms of suppression of defect states benefiting from Co ion doping were discussed based on density functional theory calculations. The results provided in this work will pave the way for development of high-performance and stable MAPbI3 PDs in the future.

Fabrication of UV-C photodetector with ultimate stability in extreme space environments (radiation, low temperature) using aerosol-deposited Ga2O3

We report on the fabrication and characterization of a Ga2O3-based UV-C photodetector using the aerosol deposition (AD) method. By optimizing the size and crystallinity of the Ga2O3 powder, we were able to obtain a uniform thin film with high transmittance (70–80%) without the need for additional heat treatment or high vacuum environments. The resulting Ga2O3 film exhibited a high and selective response to 254 nm wavelength light, even without any treatment, and remained stable when exposed to γ-radiation. The photodetector also performed well in extreme temperatures (−196 °C–150 °C), making it suitable for use in harsh environments, such as the space industry. Our findings demonstrate the potential of the AD method for the fabrication of high-quality Ga2O3 thin films for photodetector applications.

Improved Perovskite CH3NH3PbI3 Thin Films by ZIF‐67 Additive Assisted Co Ion Doping toward High‐Performance and Stable Photodetectors

AbstractLead halide perovskites are considered important materials for the fabrication of high‐performance optoelectronic devices. However, the poor quality of thin films with abundant grain boundaries and defect states greatly lower the performance and stability of as‐fabricated devices. In the present work, the growth of improved perovskite CH3NH3PbI3 thin films through Co‐based zeolite imidazole framework (ZIF‐67) additive assisted Co ion doping is reported. Investigation of the morphological, structural, optical, and electrical properties shows that the Co ion doped CH3NH3PbI3 (CH3NH3Pb0.98Co0.02I3) thin films exhibit low grain boundaries, low defect states, and improved structural stabilities. The positive roles of suppression of defect states are further demonstrated by improved performance and stability of photodetectors based on CH3NH3Pb0.98Co0.02I3 thin films. Finally, density functional theory calculations are performed to reveal the mechanisms of passivation of undercoordinate Pb2+ vacancy defect states by Co ion doping. The results provided in this work will pave the way toward the fabrication of high performance and stable perovskite photodetectors in the future.

Self-powered broadband photodetector based on Bi2Se3/GaN pn mixed-dimensional heterojunction with boosted responsivity

Self-powered broadband photodetectors (SPBDs) have received considerable attention because of their significance in optoelectronic applications. However, limited by problems inherent to the material, such as high dislocation density, complex heteroepitaxy processing of bulk materials, and the small photoabsorption cross section in atomically thin layers of two-dimensional materials, SPBD photodetectors with both a wide detection range and attractive response characteristics are difficult to fabricate. To address this difficulty, herein the synthesis of n-Bi2Se3/p-GaN mixed-dimensional heterojunctions by the transfer method and their assembly into SPBD photodetectors are described. This photodetector offers both a wide spectral response range (ultraviolet to mid-infrared) and excellent response characteristics. The high responsivity (24554 A/W, 3V), remarkable Ion/Ioff (223.8), and rapid rise and decay times (τr = 0.063 s and τd = 0.043 s) benefit from both the built-in electric field of the pn junction and the fast electron transport on the surface of topological insulator Bi2Se3. The results of this research should facilitate the use of this emerging material for the design and fabrication of high-performance SPBD photodetectors.

High-Throughput Mechanical Exfoliation for Low-Cost Production of van der Waals Nanosheets.

A method is presented for scaling up the production of flakes of van der Waals materials via mechanical exfoliation. Using a roll-to-roll setup and an automatized, massive parallel exfoliation process, adhesive tapes with a high density of nanosheets of van der Waals materials are produced. The technique allows for obtaining a good trade-off between large lateral size and excellent area scalability, while also maintaining low cost. The potential of the method is demonstrated through the successful fabrication of field effect transistors and flexible photodetectors in large batches. This low-cost method to produce large area films out of mechanically exfoliated flakes is very general, and it can be applied to a variety of substrates and van der Waals materials and, moreover, it can be used to combine different van der Waals materials on top of each other. Therefore, it is believed that this production method opens an interesting avenue for fabrication of low-cost devices while maintaining a good scalability and performance.

Fabrication and Enhancement of Organic Photodetectors Based on Iron Phthalocyanine Films

Iron–phthalocyanine (FePc) organic photoconductive detector was fabricated using pulsed laser deposition (PLD) technique to work in ultraviolet (UV) and visible regions. The organic semiconductor material (iron phthalocyanine) was deposited on n-type silicon wafer (Si) substrates at different thicknesses (100, 200 and 300) nm. FePc organic photoconductive detector has been improved by two methods: the first is to manufacture the detector on PSi substrates, and the second is by coating the detector with polyamide–nylon polymer to enhance the photoconductivity of the FePc detector. The current–voltage (I–V) characteristics, responsivity, photocurrent gain, response time and the quantum efficiency of the fabricated photoconductive detector were measured. The performance of the fabricated detector was taken under dark and illumination using two types of light sources: UV LED with wavelength (365[Formula: see text]nm), power of (10[Formula: see text]W) and Tungsten lamp with wavelength range between (500–800) nm and the optical power of (250[Formula: see text]W). The photoresponse enhancement was improved by coating the FePc films with 200[Formula: see text]nm of polyamide nylon polymer. This type of coating, which can be considered as a surface treatment, highly increased the photoresponse of the fabricated FePc UV detector. The results show that the responsivity increased four orders of magnitudes more than the responsivity of the uncoated FePc film. The effects of the coated polymers on the responsivity and the response time of the detector were investigated.

Al2O3 barrier layer for enhancing UV to visible rejection ratio in p-Si/n-MgZnO heterojunction visible blind UV photodetectors

The fabrication of visible blind ultraviolet photodetectors based on p-Si/n-MgxZn1-xO heterojunction is challenging due to the generation of visible photoresponse caused by the drift of visible light generated electrons from p-silicon to n-MgxZn1-xO across the interface. Here, it is shown that by incorporating a thin ∼30 nm Al2O3 interlayer at the heterojunction, the UV-to-visible rejection ratio in p-Si/n-Mg0.25Zn0·75O photodetectors can be significantly enhanced. The Al2O3 interlayer inserted between n-Mg0.25Zn0·75O and p-Si serves as an effective blocking layer against the transport of visible light-generated electrons from p-Si to n-Mg0.25Zn0·75O, thereby suppressing the visible photoresponse. As a result, the UV-to-visible rejection ratio was improved by approximately three orders of magnitude, with a peak responsivity of 0.17 mA/W at 270 nm and a reverse bias of 0.5 V. This high degree of visible blindness of p-Si/n-Mg0.25Zn0·75O heterojunction photodetectors with an Al2O3 barrier layer holds promise for next-generation visible-blind UV photodetection applications.

A flexible self-powered UV–Vis photodetector based on Successive Ionic Layer Adsorption and Reaction (SILAR) deposited CdS on asymmetric contacts

Self-powered photodetectors exhibiting broadband spectral responses have drawn significant attention owing to their zero-power consumption, high sensitivity, and enhanced light-matter interaction. However, considering the existing complex fabrication processes for self-powered devices, facile fabrication schemes that can be performed at room temperature and are scalable are highly desirable. This work demonstrates a metal-semiconductor-metal (MSM) based flexible, self-powered photodetector employing Successive Ionic Layer Adsorption and Reaction (SILAR) deposition of CdS directly on a paper substrate with interdigitated Asymmetric contacts, namely of pencil-drawn graphite and silver paste. Upon light illumination, a built-in field is generated due to the asymmetry in the fermi levels of the metal contacts, supporting efficient carrier separation. The as-fabricated device extends its absorbance from Ultraviolet (UV) to Visible (Vis) spectra, with the highest peak absorption around 520 nm. Further, the device exhibits a responsivity of 6.56 mA/W and 1500 mA/W and detectivity of 2.3 × 108 Jones and 5.66 × 1010 Jones when illuminated with Visible (intensity-0.0125 mW/cm2) and UV (intensity-2.50 mW/cm2) lights respectively. Without any external power, the device showed response times of 0.11 s and 1.42 s when subjected to UV and Vis irradiations. This detector also exhibited superior resistance to bending stress and retained its performance even after multiple bending cycles (∼1000). Hence, the facile, low-cost, and room-temperature SILAR deposition technique-assisted photodetector fabrication paves the way for developing other high-performance and flexible photodetectors for various optoelectronic applications.

Fully depleted vdW heterojunction based high performance photovoltaic photodetector

Van der Waals (vdW) heterojunctions, with their unique electronic and optoelectronic properties, have become promising candidates for photodetector applications. Amplifying the contribution of the depletion region in vdW heterojunction, which would enhance both of the collection efficiency and speed of the photogenerated carriers, presents an effective strategy for achieving high performance vdW heterojunction photodetectors. Herein, a fully depleted vdW heterojunction photodetector is built on two-dimensional (2D) semiconductor materials (GaTe and InSe) layered on a pattered bottom electrode in vertical structure, in which the generation and motion of carriers are exclusively achieved in the depletion region. Attributed to the intrinsic built-in electric field, the elimination of series resistance and the depletion region confinement of carriers, the as-fabricated photodetector exhibits prominent photovoltaic properties with a high open-circuit voltage of 0.465 V, as well as photoresponse characteristics with outstanding responsivity, detectivity and photoresponse speed of 63.7 A/W, 3.88 × 1013 Jones, and 32.7 μs respectively. The overall performance of this fully depleted GaTe/InSe vdW heterojunctions photodetectors are ranking high among the top level of 2D materials based photodetectors. It indicates the device architecture can provide new opportunities for the fabrication of high-performance photodetectors.

Fabrication of UV Photodetectors Based on Photoelectrochemically Etched Nanoporous Silicon: Effect of Etchants Ratio

Despite several attempts to enhance the electrical and charge carrier transport characteristics of porous silicon (PSi), the requisite conditions for optimally synthesizing n-PSi with appealing optoelectronic properties are yet to be achieved. Therefore, this research explores the effect of the chemical ratio of precursor materials (HF:C2H6O:H2O2) on the surface morphology, crystalline structure, and optical and electric properties of PSi. The PSi was produced by photoelectrochemical etching followed by anodization of the n-type Si under light illumination. The properties of the as-prepared PSi were studied by means of microscopic and spectroscopic techniques. The HF:C2H6O:H2O2 chemical ratio was optimized at 2 : 1 : 1. A metal–semiconductor–metal (MSM) ultraviolet photodetector (Pt/n-PSi/Pt) was fabricated, which exhibited high performances under UV light (365 nm) illumination. The photodetector was shown to be highly stable and reliable with a rapid rise time of 0.56 s at a bias voltage of +5 V. The MSM photodetector displayed responsivity (Rp) of 9.17 A/m at 365 nm, which significantly exceeds the values reported for TiC/porous Si/Si in some contemporary research. The photodetector fabricated from n-PSi, synthesized at an optimum chemical ratio (2 : 1 : 1) exhibited the best photodetection performance, possibly due to the high porosity and defect-free state of the n-PSi thin films.

Non-ultrawide bandgap CsPbBr3 nanosheet for sensitive deep ultraviolet photodetection

In this study, we report the fabrication of a sensitive deep ultraviolet (DUV) photodetector by using CsPbBr3 nanosheets synthesized through confined-space growth at room temperature. The peak photoresponse of the device upon illumination blueshifts with decreasing thickness and a 68 nm CsPbBr3 nanosheet based device displays a peak response to 265 nm illumination, showing responsivity and specific detectivity of 85 mA/W and 4.05 × 1011 Jones at 3 V bias, respectively. Theoretical simulation reveals that the blueshift is associated with the wavelength-dependent absorption coefficient of CsPbBr3 nanosheet: incident light with shorter wavelengths can be absorbed on the superficial surface, while long-wavelength light has a larger penetration depth, leading to dominant DUV absorption in thinner CsPbBr3 nanosheet. This work will shed light on the facile and cost-effective fabrication of DUV photodetectors from non-ultrawide bandgap (UWBG) all-inorganic perovskite materials.

Self-powered ultraviolet/visible photodetector based on CuBi2O4/PbZr0.52Ti0.48O3 heterostructure

Ferroelectric materials with significant remnant electric polarization have recently gained research focus for the fabrication of self-power photodetectors due to their photovoltaic effect. However, the photodetectors based on ferroelectric materials display poor performance owing to their weak photovoltaic effect of the ferroelectric depolarization field (Ed) on photo-generated charge carrier separation. In this work, we fabricate self-powered photodetectors based on CuBi2O4/PZT heterostructure. The heterojunction reveals a photoresponsivity of 0.24 mA/W and a detectivity of 2.40 × 1010 Jones under 0 V bias with a maximum 7.51 μW/cm2 illumination intensity at 425 nm, which is substantially improved compared to PZT-only device. The observed rise and fall time of the composite CuBi2O4/PZT thin film is around 24 and 46 ms, respectively, which is faster than that of PZT photodetector (67 and 106 ms). Moreover, the photocurrent CuBi2O4/PZT of device is observed to be 12.7 × 10−10 A in the downpoling state and 6.28 × 10−10 A in upward poling state, revealing that the direction of polarization field can modulate the photocurrent. This work provides a promising strategy for fabricating ferroelectric heterojunction photodetectors with enhanced performance.

Noticeable effect of coating temperature on Co3O4 thin films developed through low-cost nebulizer spray pyrolysis for photo-sensing applications

Cobalt oxide thin films are synthesized at various temperatures from 275 to 375 °C using a nebulizer spray pyrolysis technique. Different characterization approaches are used to investigate the effects of coating temperature on the characteristics of coated thin films. The deposited films have a cubic structure with a preferred orientation along the (111) direction. Field Emission Scanning Electron Microscope (FESEM) reveals the grain size of the samples as the coating temperature rises. The energy dispersive x-ray analysis (EDS) spectra confirm that the growing film is primarily made up of Co and O. The optical absorption spectra show an increase in absorption with increasing coating temperature. The band-gap energy values are lowered by 2.12, 2.10, 2.09, 2.01, and 2.05 eV with respect to the coating temperatures of 275, 300, 325, 350, and 375 °C, respectively. The observed photoluminescence(PL) spectra exhibit the band edge and defect-based emissions for all the films. Studies of current (vs) voltage revealed ohmic nature up to 350 °C coating temperature. At coating temperature 375 °C hysteretic behavior of film is observed because of the increasing number of vacancies and defective sites, which act as trap of charge carriers. The photo-detection capabilities of these coated Co3O4 thin films were investigated using optoelectronic characteristics. The optical and electrical properties have also been controlled by the fusing temperature. The Co3O4 (350 °C) produce high photocurrent (8.84 × 10−7A), external quantum efficiency (11.6%), detectivity (3.5 × 109 Jones), responsivity (4.99 × 10−2 AW−1) and has the shortest rise/decay time among the constructed photo-detectors. These findings show the tuning of the properties of Co3O4 by optimizing the coating temperature for the fabrication of effective photo-detectors.