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Switchable Schottky contacts: Simultaneously enhanced output current and reduced leakage current
摘要： Metal-semiconductor contacts are key components of nanoelectronics and atomic-scale integrated circuits. In these components Schottky diodes provide a low forward voltage and a very fast switching rate but suffer the drawback of a high reverse leakage current. Improvement of the reverse bias characteristics without degrading performance of the diode at positive voltages is deemed physically impossible for conventional silicon-based Schottky diodes. However, in this work we propose that this design challenge can be overcome in the organic-based diodes by utilizing reversible transitions between distinct adsorption states of organic molecules on metal surfaces. Motivated by previous experimental observations of controllable adsorption conformations of anthradithiophene on Cu(111), herein we use density functional theory simulations to demonstrate the distinct Schottky barrier heights of the two adsorption states. The higher Schottky barrier of the reverse bias induced by chemisorbed state results in low leakage current; while the lower barrier of the forward bias induced by physisorbed state yields a larger output current. The rectifying behaviors are further supported by nonequilibrium Green's function transport calculations.
关键词： van der Waals forces,Schottky contacts,Schottky barrier height,reverse leakage current,bistable state
更新于2025-09-23 15:23:52
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Temperature-Dependent Electrical Characteristics of β-Ga <sub/>2</sub> O <sub/>3</sub> Diodes with W Schottky Contacts up to 500°C
摘要： The development of thermally stable contacts capable of high temperature operation are necessary for Ga2O3 high power rectifiers. We have measured the electrical characteristics of sputter-deposited W Schottky contacts with Au overlayers for reducing sheet resistance on n-type Ga2O3 before and after device operation up to 500°C. Assuming thermionic emission is dominant, the extracted barrier height decreases with measurement temperature from 0.97 eV (25°C) to 0.39 eV (500°C) while showing little change from its initial value of 0.97 eV after cooling down from each respective operation temperature. The room temperature value is comparable to that obtained by determining the energy difference between binding energy of the Ga 3d core level and the valence band of the Ga2O3 when W is present, 0.80 ± 0.2 eV in this case. The Richardson constant was 54.05 A.cm?2.K?2 for W and the effective Schottky barrier height at zero bias (eφb0) was 0.92 eV from temperature-dependent current-voltage characteristics. The temperature coefficient for reverse breakdown voltage was 0.16 V/K for W/Au and 0.12 V/K for Ni/Au. The W-based contacts are more thermally stable than conventional Ni-based Schottkies on Ga2O3 but do show evidence of Ga migration through the contact after 500°C device operation.
关键词： electrical characteristics,thermal stability,high temperature operation,Ga2O3,Schottky contacts
更新于2025-09-23 15:23:52
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Schottky Contacts on Polarity-Controlled Vertical ZnO Nanorods
摘要： Polarity-controlled growth of ZnO by chemical bath deposition provides a method for controlling the crystal orientation of vertical arrays of nanorods. The ability to define the morphology and structure of the nanorods is essential to maximising the performance of optical and electrical devices such as piezoelectric nanogenerators; however, well-defined Schottky contacts to the polar facets of the structures have yet to be explored. In this work, we demonstrate a process to fabricate metal-semiconductor-metal device structures from vertical arrays with Au contacts on the uppermost polar facets of the nanorods and show the O-polar nanorods (~0.44 eV) have a greater effective barrier height than the Zn-polar nanorods (~0.37 eV). Oxygen plasma treatment is shown by Cathodoluminescence (CL) spectroscopy to reduce mid-gap defects associated with radiative emissions that improves the Schottky contacts from weakly-rectifying to strongly-rectifying. Interestingly, the plasma treatment was shown to have a much greater effect in reducing the number of carriers in O-polar nanorods through quenching of the donor-type substitutional hydrogen on oxygen sites (HO) when compared to the zinc vacancy related hydrogen defect complexes (VZn, Hn) in Zn-polar nanorods that evolve to lower coordinated complexes. The effect on HO in the O-polar nanorods coincided with a large reduction in the visible range defects producing a lower conductivity and creating the larger effective barrier heights. This combination can allow radiative losses and charge leakage to be controlled enhancing devices such as dynamic photodetectors, strain sensors, and LEDs while showing the O-polar nanorods can outperform Zn-polar nanorods in such applications.
关键词： ZnO,Cathodoluminescence,Electrical Transport,Polarity,Schottky Contacts,Nanorods,Defects
更新于2025-09-23 15:21:01
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Industrial Applications of Nanomaterials || Nanomaterials-based UV photodetectors
摘要： Photodetectors are essential elements applied in video imaging, optical communications, biomedical imaging, security, night-vision, gas sensing, and motion detection, which possess the ability to transform light into electrical signals precisely. As the scale and diversity of application areas are growing, the need for innovative photodetection platform technologies with higher performance in terms of speed, efficiency or wavelength range, as well as material flexibility, transparency, and complementary metal-oxide-semiconductor (CMOS) integrability, is becoming more critical. In the past decades, extensive efforts have been devoted to explore the next generation of photodetector materials, such as In2Te3, ZnO, and GaN, with low noise, high photosensitivity, and good stability. However, many of these novel photodetector materials still suffer from limited photocurrent and photoresponse speed.
关键词： Nanomaterials,Schottky contacts,photoconductive gain,photodetection mechanism,photoresistors,linear dynamic range,responsivity,external quantum efficiency,photodiodes,specific detectivity,UV photodetectors
更新于2025-09-19 17:13:59
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Beyond Gold: Spin‐Coated Ti <sub/>3</sub> C <sub/>2</sub> ‐Based MXene Photodetectors
摘要： 2D transition metal carbides, known as MXenes, are transparent when the samples are thin enough. They are also excellent electrical conductors with metal-like carrier concentrations. Herein, these characteristics are exploited to replace gold (Au) in GaAs photodetectors. By simply spin-coating transparent Ti3C2-based MXene electrodes from aqueous suspensions onto GaAs patterned with a photoresist and lifted off with acetone, photodetectors that outperform more standard Au electrodes are fabricated. Both the Au- and MXene-based devices show rectifying contacts with comparable Schottky barrier heights and internal electric fields. The latter, however, exhibit significantly higher responsivities and quantum efficiencies, with similar dark currents, hence showing better dynamic range and detectivity, and similar sub-nanosecond response speeds compared to the Au-based devices. The simple fabrication process is readily integratable into microelectronic, photonic-integrated circuits and silicon photonics processes, with a wide range of applications from optical sensing to light detection and ranging and telecommunications.
关键词： work-function,MXene,semiconductors,Schottky contacts,photodetectors
更新于2025-09-11 14:15:04
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High-Temperature β-Ga$_2$O$_3$ Schottky Diodes and UVC Photodetectors using RuOx Contacts
摘要： High-temperature β-Ga2O3 Schottky diodes with very low leakage currents, capable of sensitive UVC detection at 350 oC, were fabricated on 201 β-Ga2O3 single crystal substrates using intentionally-oxidized ruthenium (RuOx) Schottky contacts (SCs), with x = ~2.1. These RuOx:β-Ga2O3 SCs were characterized by rectification ratios of more than 1010 at ± 3 V and very low reverse leakage current densities of less than 1 nAcm-2 (~1 pA) at ?3.0 V, that were unchanged from 24 to 350 oC. These very low high-temperature leakage currents were due to their extremely high Schottky barriers of 2.2 eV at 350 oC, that were stable against repeated operation at this temperature. Although not optimized for photodetection, these SCs could detect UVC (λ = 248 nm) radiation at a temperature of 350 oC with a UVC/dark current ratio of ~103. The very high and thermally stable rectifying barriers of these RuOx:β-Ga2O3 SCs makes them strong candidates for use in high temperature β-Ga2O3 rectifying diodes and UVC photodetectors.
关键词： High Temperature Devices,Schottky Contacts,RuO2,Ga2O3,Ruthenium Dioxide,UV Photodetectors
更新于2025-09-11 14:15:04
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Gaussian distribution in current-conduction mechanism of (Ni/Pt) Schottky contacts on wide bandgap AlInGaN quaternary alloy
摘要： The current-conduction mechanisms of the as-deposited and annealed at 450 °C (Ni/Pt) Schottky contacts on AlInGaN quaternary alloy have been investigated in the temperature range of 80–320 K. The zero-bias barrier height (BH) (ΦB0) and ideality factor (n) of them were evaluated using thermionic emission (TE) theory. The ΦB0 and n values calculated from the I-V characteristics show a strong temperature dependence. Such behavior of ΦB0 and n is attributed to Schottky barrier inhomogeneities. Therefore, both the ΦB0 vs n and ΦB0 vs q/2kT plots were drawn to obtain evidence on the Gaussian distribution (GD) of the barrier height at the metal/semiconductor interface. These plots show two different linear parts at low and intermediate temperatures for as-deposited and annealed Schottky contacts. Thus, the mean value of ΦB0 and standard deviation (σ0) was calculated from the linear parts of the ΦB0 vs q/kT plots for both samples. The values of the effective Richardson constant (A*) and mean BH were obtained from the modified Richardson plots which included the effect of barrier inhomogeneity. These values of Richardson constant and barrier height for as-deposited contacts were found to be 19.9 A cm?2 K?2 and 0.59 eV, respectively, at low temperature, but 43.3 A cm?2 K?2 and 1.32 eV, respectively, at intermediate temperatures. These values of Richardson constant and barrier height for annealed contacts were found to be 19.6 A cm?2 K?2 and 0.37 eV, respectively, at low temperature, but 42.9 A cm?2 K?2 and 1.54 eV, respectively, at intermediate temperatures. It is clear that the value of the Richardson constant obtained for as-deposited and annealed samples by using double-GD for intermediate temperatures is close to the theoretical value of AlInGaN (=44.7 A cm?2 K?2). Therefore, I-V-T characteristics for the as-deposited and annealed Schottky contacts in the temperature range of 80–320 K can be successfully explained based on TE theory with double-GD of the BHs.
关键词： AlInGaN,barrier height,Schottky contacts,Gaussian distribution,thermionic emission
更新于2025-09-11 14:15:04
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Temperature dependent electrical characteristics of rectifying graphitic contacts to p-type silicon
摘要： Graphitic contacts to semiconductors have been shown to provide highly rectifying current-voltage characteristics coupled with high thermal/chemical stability. Energetically deposited graphitic contacts to p-type Si have exhibited rectification ratios (at ± 1.0 V) up to 106:1 and ideality factors approaching unity. Here, we report temperature dependent current-voltage (I-V-T) measurements performed on such devices. The measurements and subsequent analysis show that during energetic carbon deposition, deleterious oxide/contaminants are removed from the Si substrate surface. The Richardson constant of the p-type Si extracted from the I-V-T measurements agrees with the theoretical value, indicating that the surface contaminants are removed without significant damage to the underlying Si. Therefore, by energetic deposition of C on Si, C-Si junctions can be formed with low lateral inhomogeneity and low interface defect density. These attributes of the junctions enable the observed near-ideal Schottky diode characteristics.
关键词： graphenic carbon,electronic materials,graphitic carbon,Schottky contacts
更新于2025-09-10 09:29:36
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Gallium Oxide || Schottky contacts to β-Ga2O3
摘要： The success of β-Ga2O3 as the wide-bandgap semiconductor platform for ultrahigh efficiency electronic and optoelectronic devices relies on the ability to control the properties of ohmic and rectifying, or Schottky, contacts on this material. This chapter focuses on the current status of research and development of Schottky contacts on β-Ga2O3: the materials and structures used and their corresponding electrical properties.
关键词： Schottky contacts,β-Ga2O3,electronic devices,optoelectronic devices,wide-bandgap semiconductor
更新于2025-09-10 09:29:36
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Indium-Gallium-Zinc-Oxide Schottky Synaptic Transistors for Silent Synapse Conversion Emulation
摘要： Silent synapses play an important role in synaptic plasticity and the nervous system development. In this letter, indium-gallium-zinc-oxide (IGZO) Schottky electric-double-layer transistors were proposed for silent synapse conversion emulation. Silent to active conversion of such neuromorphic devices was realized by applying voltage pulses on the gate electrode of the synaptic transistor. In addition, some important synaptic behaviors such as paired-pulse facilitation and dynamic high-pass filtering were also emulated in the IGZO-based Schottky synaptic transistor after electric pulse activation.
关键词： Electric-double-layer transistors,IGZO,Neuromorphic devices,Schottky contacts
更新于2025-09-09 09:28:46