Metal-semiconductor Structures Research Articles

Electrical and dielectric behaviors of Al/SiO2-surfactant/n-Si schottky structure in wide range of voltage and frequency

SiO2 surfactant insulator into Al/n-Si metal-semiconductor (MS) structure was fabricated into Al/SiO2-surfactant/n-Si metal–insulator–semiconductor (MIS) structure and its effect on the electrical properties of the final structure was investigated. The SiO2-surfactant layer is coated on the n-Si wafer by the spin coating technique. The I-V data is used to calculate the fundamental electrical parameters of this MIS structure. The density distribution of the surface states (Nss) is computed depending on the energy at forward potential. The current conduction mechanisms (CCMs) in the MIS structure are examined at the reverse and forward biases applied. To get more accurate and reliable results, the profiles of I-V and C/(G/ω)-V are measured at a wide range of bias voltage (0.25V-4V) and frequency (1kHz-1MHz), respectively. The performance of the MIS is significant due to the basic values of electrical parameters (n, I0, Rs, Rsh, Nss, ΦB0, and Rectifying Ration (RR)) and dielectric parameters (ε′, ε″, tan δ, M′, M″, Rs, and σ) compared with the MS structure. The other electrical parameters (ND, WD, Em, ΦΒ) are extracted from the slope and intercept of the reverse bias C−2-V plot as a function of frequency. Furthermore, the profile of voltage-dependent Rs and Nss was determined using different methods from I-V and C/G-V data and examined comparatively with each other. The changes in impedance properties with frequency and voltage of the MIS are discussed in detail.

Self-Powered InGaZnO Ozone Gas Sensors Based on a Metal–Semiconductor–Metal Structure with Asymmetric Interdigitated Electrodes

Self-Powered InGaZnO Ozone Gas Sensors Based on a Metal–Semiconductor–Metal Structure with Asymmetric Interdigitated Electrodes

Enhanced sensitivity of MoS2:Er-based flexible near-infrared photodetectors via tellurium-induced interfacial charge transfer

The persistent photoconductive behavior caused by traps in the active materials usually weakens the sensitivity and stability of photodetectors. Herein, tellurium (Te) microwire and polyvinyl alcohol (PVA) composites were developed as functional flexible substrates to improve the near-infrared (NIR) photoresponse performance of MoS2:Er-based devices with the metal–semiconductor–metal structure. The flexible photodetector exhibits a rise/fall time of ∼2.9–3.1 ms, a responsivity of ∼0.28 mA W−1, and a detectivity of ∼1.41 × 1010 Jones under 808 nm irradiation. The enhanced mechanism can be attributed to the charge transfer between Te microwires and MoS2:Er films, which suppresses the dark current of the device and optimizes the generation process of electron–hole pairs under light illumination. Meanwhile, the flexibility of the device allows it to be employed in human heart rate monitoring. This work offers a simple and essential strategy for constructing integrated flexible NIR photodetectors with high performance.

Efficient and stable self-powered PbSe photodetectors via doping-induced asymmetric Cr electrodes modulation of surface work function

Conventional PbSe infrared photodetectors typically demands a substantial external electric field, posing challenges in energy-constrained environments. Self-powered photodetectors present a promising avenue for addressing such electricity-related challenges. Nevertheless, the inherent limitations of symmetric Schottky contacts in metal-semiconductor-metal (MSM) photodetectors constrain their self-powered performance, resulting in opposing photocurrents. Constructing asymmetric MSM structures usually requires intricate design or sustained external fields. In this study, we propose a novel contact engineering strategy based on iodine doping to modulate surface work functions of PbSe film. Utilizing Cr electrodes, we achieve Ohmic contact on the iodine-doped top surface of PbSe film and Schottky contact on the as-grown bottom surface. This approach establishes a self-powered PbSe infrared photodetector with an asymmetric top-bottom MSM structure. We comprehensively investigate contact engineering by investigating surface chemical states, elemental variations, and surface work functions variation. Remarkably, the photodetector demonstrates an exceptional zero-bias detectivity of 1.13 × 109 Jones, with an extremely low dark current of 3.67 pA, high Ilight/Idark ratio exceeding 104, and extremely short response times of less than 1 ms, respectively. Our work introduces a new strategy for modifying the band structure, contributing to the fabrication of high-performance self-powered photodetectors.

Electrical properties of PVC:BN nanocomposite as interfacial layer in metal-semiconductor structure

In this study, a comprehensive examination is assumed to investigate the influence of interfacial layers composed of polyvinyl chloride (PVC) and polyvinyl chloride-boron nitride (PVC: BN) on the electrical characteristics of the Au/n-Si structure. Two distinct structures, namely Au/PVC/n-Si (MPS1) and Au/PVC: BN/n-Si (MPS2), are fabricated for this purpose. The provided boron nitride (BN) nanostructures are analyzed using X-ray diffraction (XRD) patterns to determine their average crystalline size and surface morphology. Following the structural analysis, current-voltage (I–V) measurements are conducted over an extensive voltage range (± 3 V). Subsequently, the fundamental electrical properties of the developed Schottky structures are determined using various methods and compared. Experimental results indicate that the PVC: BN nanocomposite leads to an increase in the potential barrier height (BH), shunt resistance (Rsh), and rectifying rate (RR = IF/IR), while simultaneously decreasing the ideality factor (n), series resistance (Rs), and surface states density (Nss). It was discovered that the MS structure’s RR was 7 times lower than that of the MPS2 structure. Moreover, the energy-dependent Nss density is also derived using n(V) and ΦB0(V) functions. Based on the ln(IR)−VR0.5 profile at the reverse bias region, the Schottky-emission (SE) type conduction mechanism is effective for MS structures, whereas Poole-Frenkel-emission (PFE) is effective for MPS structures.

Development of Cu2O-Cu-ZnO ternary nanocomposites for high-performance photoelectrochemical non-enzymatic glucose sensor

The construction of ternary nanocomposites has shown promising prospects in photoelectrochemical (PEC) glucose sensing. In this work, cubic Cu2O-Cu-ZnO (CCZ) ternary nanocomposite was synthesized through a straightforward method. The CCZ/Nafion/GCE (glassy carbon electrode) electrode possessed excellent photo-response and was used for PEC glucose sensing. As the light intensity increased, the CCZ/Nafion/GCE electrode exhibited higher sensitivity (1.213 mA mM−1 cm−2), wider linear range (0–5 mM), shorter response time (3 s) and lower detection limit (2.10 μM). The anti-interference and stability tests proved the high stability of the CCZ-based glucose sensor. Further results confirmed that the glucose concentration detected by the CCZ-based glucose sensor was close to the results detected by a commercial sensor, indicating the application prospect of the CCZ-based PEC glucose sensor. This work provided a novel perspective for the development of ternary semiconductor-metal structure in PEC glucose sensing.

Investigation of electrical, dielectric and interface state densities of Al/p-Si structures with PTCDA interlayer under different light intensities

In our study; we investigated illumination intensity-dependent electrical and dielectric properties of the Al/p-type Si metal-semiconductor (MS) structures with perylenetetracarboxylic dianhydride (PTCDA) interface using current-voltage (I–V) and capacitance-conductance-voltage (C-G/ω--V) measurements. Thin film layer with PTCDA interface was coated on p-type Si by Spin Coating method. The structure of PTCDA organic semiconductor powder examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrical parameters such as ideality factors (n), barrier heights (Φbo), rectification ratios (RR), saturation currents (I0) and series resistances (RS) were obtained from both thermionic emission (TE) theory and Cheng theory and compared with each other. Dielectric properties such as dielectric constant (ε′), dielectric loss (ε''), loss tangent (tanδ), electrical conductivity (σac), and interface state densities (NSS) were obtained from C–V and G/ω-V measurements. It was seen that the values of ε′, ε'', tanδ, and NSS decreases with increasing illumination while σac increase with increasing illumination intensity. Experimental results show that Al/PTCDA/p-type Si semiconductor structure can improve efficiency in electronic devices.

Room temperature growth of CsPbBr3 single crystal for asymmetric MSM structure photodetector

UV–visible broadband light harvesting ability is critical for photodetectors, and all inorganic perovskite CsPbBr3 is regarded as a promising candidate as the response active material. Herein, a saturated-solution crystallization method is employed to synthesize CsPbBr3 single crystal. Temperature-dependent photoluminescence spectra with one-photon and two-photon excitation are systematically investigated, determining a large exciton binding energy of 39.8 meV. This allows the stable excitonic emission of CsPbBr3 single crystal at room temperature. Subsequently, an asymmetric structure CsPbBr3 photodetector is fabricated by using InGa alloy as the Ohmic electrode and Au as the Schottky electrode. At -8 V, the device exhibits a prominent response to the irradiation from UV to green band with a maximum responsivity of 2.56 A/W, an external quantum efficiency of 580 %, and a detectivity of 1.24 × 1013 Hz1/2 W−1. In addition, the CsPbBr3 photodetector also presents rapid response speeds at both reverse and forward bias voltages and self-powered characteristics owing to the Schottky depletion layer underneath the Au electrode. The demonstration of asymmetric metal-semiconductor-metal (MSM) structure photodetector presents a promising pathway toward next-generation CsPbBr3 optoelectronic devices.

Optoelectric response of Schottky photodiode with a PVP: ZnTiO3 nanocomposite as an interfacial layer

This work aims to study the photo-response of the fabricated silicon-based Al/PVP:ZnTiO3/p-Si photodiode (PD) in a wide range of illumination intensities. To make a metal-polymer/nanocomposite-semiconductor (MPS) PD, a thin film of PVP:ZnTiO3 nanocomposite is deposited at the interface of the metal-semiconductor (MS) structure. Information regarding the preparation and manufacturing procedures is provided. Through the examination of the current-voltage (I–V) behavior, essential electrical properties such as leakage current (I0), barrier height (ΦB0), ideality factor (n), series and shunt resistances (Rs, Rsh), energy-dependent interface states density (Nss), photocurrent (Iph), and photosensitivity (S) are acquired. The thermionic emission (TE) theory, along with the Norde and Cheung methods, is employed to calculate the parameters ΦB0, n, and Rs. The values of ΦB0 and Rs are decreased by raising the illumination intensity while the n value is increased. In addition, the illumination coefficient (α) and the value of ΦB0 in the ideal case are determined from the ΦB0-P and ΦB0-n plots. The efficiency (η) of the sample is calculated at each illumination intensity whose maximum value is 2.30 % at the intensity of 450 mW/cm2. The illumination-dependent photocurrent is investigated at the negative bias region that shows a good linear behavior in the ln(Iph)-ln(P) profile. The photosensitivity (S) of the fabricated PD is obtained as ⁓500 which is, compared with previous PDs. These findings demonstrate that the developed silicon-based MPS-type PD with a structure of Al/PVP:ZnTiO3/p-Si exhibits a good photo-response and can successfully replace traditional MS PDs in optoelectronic and photovoltaic applications.

High performance metal-semiconductor-metal ultraviolet photodetector based on mixed-dimensional TiO2/CsPbBr3 heterostructures

Zero-dimensional (0D) and one-dimensional (1D) mixed heterostructure semiconductors can bring superior electrical and optoelectronic performances due to the synergistic advantages of different dimensionalities. Here, a metal-semiconductor–metal (MSM) ultraviolet (UV) photodetector based on 1D-0D TiO2/CsPbBr3 heterostructure semiconductor is constructed, which exhibits excellent photodetection performance. A back-to-back Schottky contact is formed in the MSM (Au/TiO2/Au) structure due to the large band-energy bending resulted from the abundant surface-states at 1D-TiO2 surface. Under an applied voltage, a small saturation current flows through the device. Benefiting from the decoration of CsPbBr3 QDs, the dark current of MSM photodetectors can be further suppressed, and producing the improved on/off ratio (I light/I dark), photoresponsivity (R λ ), and detectivity (D*). PL properties study suggested that an energy transfer is occurred between the 0D-CsPbBr3 and 1D-TiO2. The TiO2/CsPbBr3 heterojunctions are beneficial for photo-induced charge transfer in hetero-interface because of the type-II energy-band alignment, but not non-radiative energy transfer from 0D-CsPbBr3 to 1D-TiO2. On the whole, this study depicts a fascinating coupling architecture of mixed-dimensional materials toward implementing low-cost and high-performance optoelectronic devices.

Experimental and theoretical analysis of a Visible-Light photodetector based on cadmium sulfide fabricated on interdigitated electrodes

The wide range of applications for photodetectors, such as in space, industry, medical, and military, has garnered significant research attention in recent years. In this study, an n-type single-layer photodetector based on a Cu/CdS/Cu metal–semiconductor-metal structure with a micro interdigitated electrode array (IDE) was fabricated. The surface morphology and absorption properties of the CdS thin films were characterized using atomic force microscopy, scanning electron microscopy, and UV–Vis spectrometry. The photo response characteristics of the photodetector were recorded across wavelengths of 400–780 nm. The optoelectronic analyses of the structure revealed a maximum responsivity value of approximately 98.73 % at 405 nm incident light, with a high response time of about 0.12 s. Furthermore, the structure was theoretically studied and simulated, with the simulation results demonstrating good agreement with the measured experimental evidence. The above results indicate that the present CdS photodetector holds excellent potential for use in high-sensitivity optoelectronic integrated circuits.

Exploration of a wide bandgap semiconducting supramolecular Mg(II)-metallohydrogel derived from an aliphatic amine: a robust resistive switching framework for brain-inspired computing

A rapid metallohydrogelation strategy has been developed of magnesium(II)-ion using trimethylamine as a low molecular weight gelator in water medium at room temperature. The mechanical property of the synthesized metallohydrogel material is established through the rheological analysis. The nano-rose like morphological patterns of Mg(II)-metallohydrogel are characterized through field emission scanning electron microscopic study. The energy dispersive X-ray elemental mapping analysis confirms the primary gel forming elements of Mg(II)-metallohydrogel. The possible metallohydrogel formation strategy has been analyzed through FT-IR spectroscopic study. In this work, magnesium(II) metallohydrogel (Mg@TMA) based metal–semiconductor-metal structures have been developed and charge transport behaviour is studied. Here, it is confirmed that the magnesium(II) metallohydrogel (Mg@TMA) based resistive random access memory (RRAM) device is showing bipolar resistive switching behaviour at room temperature. We have also explored the mechanism of resistive switching behaviour using the formation (rupture) of conductive filaments between the metal electrodes. This RRAM devices exhibit excellent switching endurance over 10,000 switching cycles with a large ON/OFF ratio (~ 100). The easy fabrication techniques, robust resistive switching behaviour and stability of the present system makes these structures preferred candidate for applications in non-volatile memory design, neuromorphic computing, flexible electronics and optoelectronics etc.

Self-powered AlGaN-based MSM solar-blind ultraviolet photodetectors with high Al-content AlxGa1−xN/AlyGa1−yN asymmetrical heterostructure

An Al0.4Ga0.6N-based metal–semiconductor–metal (MSM) ultraviolet (UV) photodetector (PD) based on intentionally asymmetrical polarized Al0.55Ga0.45N/Al0.4Ga0.6N/Al0.65Ga0.35N heterostructure has been fabricated and investigated, which achieves the self-powered capabilities. Operated at zero bias, the device presents an ultralow dark current of 7.8 × 10−13 A, a high peak responsivity of 0.04 A/W at ∼275 nm, a cut-off wavelength at ∼285 nm, and a corresponding detectivity of 3.1 × 1012 Jones. In comparison, the device with symmetrical heterostructure has no response at 0 V, confirming the effect of the proposed asymmetrical MSM structure. Furthermore, it is expressly demonstrated that the structure provides an asymmetrical energy band due to different barrier heights at the metal/Al0.4Ga0.6N and metal/Al0.55Ga0.45N/Al0.4Ga0.6N Schottky contacts and enhances the built-in electric field in the Al0.4Ga0.6N active layer owing to its polarization effect through simulations theoretically. Therefore, the improvement of photogenerated carrier transport can be obtained at 0 V, contributing to the high-performance self-powered UV PD.

Low resistance large area terahertz detector based on antimony telluride thin film

Terahertz technology has great potential for various applications in fields like biomedicine, astronomy, communications, and security inspection. Therefore, terahertz detectors that can operate at room temperature with fast response times, high sensitivity, wide detection bandwidth, and can be seamlessly integrated. To achieve this, a metal–semiconductor-metal structure with a subwavelength gap is used, which creates an electromagnetic induced potential well within the semiconductor by utilizing the antisymmetric electric field of terahertz radiation. This structure allows for the injection and retention of electrons from the metal, enhancing electrical conductivity. Experimental results have shown that reducing the spacing between the forked finger electrodes improves the detection performance of the device. At room temperature, with a bias voltage of 1 V and 0.28 THz radiation, the device achieves an equivalent noise power of 9.76 × 10−13 W/Hz/2 and a detection rate of 2.41 × 1011cm Hz1/2W−1. Additionally, the device's simple structure and large effective detection area make it suitable for producing low-resistance and large-area terahertz detectors.

Construction of organic/GaN heterostructures for DUV-to-NIR broadband photodetection.

Herein, a broadband photodetector (BPD) is constructed with consistent and stable detection abilities for deep ultraviolet to near-infrared spectral range. The BPD integrates the GaN template with a hybrid organic semiconductor, PM6:Y6, via the spin-coating process, and is fabricated in the form of asymmetric metal-semiconductor-metal structure. Under an optimal voltage, the device shows consistent photoresponse within 254 to 850 nm, featuring high responsivity (10 to 60 A/W), photo-to-dark-current ratio over 103, and fast response time. These results show the potential of such organic/GaN heterojunctions as a simple and effective strategy to build BPDs for a reliable photo-sensing application in the future.

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.

Fine-tuning biexcitons-plasmon coherent states in a single nanocavity

Abstract A tunable plexcitonic material that sustains multimode hybridization is highly desirable, which is vital for advanced quantum devices. However, the research about regulations of biexcitons-plasmon coherent states has rarely been reported. Here we apply single-nanoparticle scattering spectroscopy correlative with SEM imaging to identify biexcitons-plasmon interaction in a metal-semiconductor hybrid structure composed of a single Au@Ag nanoparticle, J-aggregates molecules and tungsten disulfide (WS2) monolayer. The mode competition within the localized plasmonic hotspots (∼240 nm3) is revealed by continuously regulating the J-aggregates spacer. Two distinct anticrossings are observed at both excitons resonances, and large double Rabi splittings (137 meV and 124 meV) are obtained successfully. We establish experimentally that J-aggregates and WS2 monolayer are responsible for the middle polariton states, while plasmon rarely contributes. Further calculations show that plasmonic nanocavity enables coherent energy exchange with different excitons by providing a highly enhanced localized E-field. In addition, we find that the multimode coupling strengths can be efficiently tuned by changing the cavity morphology and environment temperature, where the tuning spectral accuracy can reach up to 1 nm. Our findings uncover the distinctive properties of biexcitons-plasmon polaritons, suggest an easily obtainable multiqubit states platform, and open up a new way to construct nanoscale photonic devices.

On frequency and voltage dependent physical characteristics and interface states characterization of the metal semiconductor (MS) structures with (Ti:DLC) interlayer

In this present study, the electrical parameters of Al/p-Si (MS) structures with (Ti-doped DLC) interfacial layer were investigated between 1 kHz and 4 MHz utilizing impedance-spectroscopy method. The (Ti:DLC) interlayer grown by electrochemical deposition method and its structural characterization was performed by SEM, EDX, and XPS methods. The XPS results show that the chemical-structure of the interlayer has 15.53% Ti, 50.18% O, 18.15% C, 4.14% Si, 10.24% N after annealing. The concentration of acceptor-atoms (NA), Fermi-energy (EF), depletion-layer thickness (Wd), maximum electric-field (Em), and barrier-height (ΦB(C–V)) values were calculated from the C−2-V plots as 4.78 × 1015cm−3, 0.20eV, 3.28x10−5cm, 2.40 × 104 V/cm, 0.594eV at 20 kHz and 4.96 × 1015cm−3, 0.199eV, 4.14x10−5cm, 3.14 × 104 V/cm, 0.849eV at 4 MHz, respectively. The surface-states (Nss) and their life-time (τ) were obtained from conductance-method as 0.77 × 1013/(eVcm2) and 1.40x10−3s at 0.05V and 1.57 × 1013/(eVcm2) and 1.74x10−5s at 1.00 V, respectively.

Alpha-phase gallium oxide-based UVC photodetector with high sensitivity and visible blindness

This paper describes the heteroepitaxial growth of high-quality alpha-phase gallium oxide (α-Ga2O3) on a sapphire substrate without a buffer layer via the hydride vapor phase epitaxy method. Here, compressive strain arising from the difference in lattice constants between the substrate and α-Ga2O3 is relieved near the interface, resulting in a high crystal quality of 32.72 arcsec (full width at half maximum value) in the high-resolution x-ray diffraction 2θ scan spectrum. Subsequently, the fabricated hetero α-Ga2O3-based photodetector with a metal–semiconductor–metal structure operating under ultraviolet radiation in the C-band (UVC) demonstrates a high UVC responsivity of 5 × 102 A W−1 and a high visible blindness of 8.14 × 104 at 235 nm. The photodetector utilizes photogenerated holes trapped near the interface of the metal electrode, inducing amplified electron current flow. The developed hetero α-Ga2O3-based UVC photodetector can be used to detect early signs of fire, flames, or corona discharge in visible light environments for social and industrial safety applications.

High performance solar-blind deep ultraviolet photodetectors via β-phase (In0.09Ga0.91)2O3 single crystalline film

We successfully fabricate a high performance β-phase (In0.09Ga0.91)2O3 single-crystalline film deep ultraviolet (DUV) solar-blind photodetector. The 2-inches high crystalline quality film is hetero-grown on the sapphire substrates using the plasma-assisted molecular beam epitaxy (PA-MBE). The smooth InGaO single crystalline film is used to construct the solar-blind DUV detector, which utilized an interdigitated Ti/Au electrode with a metal–semiconductor–metal structure. The device exhibits a low dark current of 40 pA (0 V), while its UV photon responsivity exceeds 450 A/W (50 V) at the peak wavelength of 232 nm with illumination intensity of 0.21 mW/cm2 and the UV/VIS rejection ratio (R 232 nm/R 380 nm) exceeds 4 × 104. Furthermore, the devices demonstrate ultrafast transient characteristics for DUV signals, with fast-rising and fast-falling times of 80 ns and 420 ns, respectively. This excellent temporal dynamic behavior can be attributed to indium doping can adjust the electronic structure of Ga2O3 alloys to enhance the performance of InGaO solar-blind detectors. Additionally, a two-dimensional DUV scanning image is captured using the InGaO photodetector as a sensor in an imaging system. Our results pave the way for future applications of two-dimensional array DUV photodetectors based on the large-scale InGaO heteroepitaxially grown alloy wide bandgap semiconductor films.