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Showing papers on "Schottky diode published in 2019"


Journal ArticleDOI
TL;DR: The prediction based on the thermionic emission theory agrees well with experimental data and a rectification behavior observed in the experiment from 273 to 340 K.
Abstract: Schottky effect of two-dimensional materials is important for nanoscale electrics. A ReSe2 flake is transferred to be suspended between an Au sink and an Au nanofilm. This device is initially designed to measure the transport properties of the ReSe2 flake. However, a rectification behavior is observed in the experiment from 273 to 340 K. The rectification coefficient is about 10. The microstructure and elements composition are systematically analyzed. The ReSe2 flake and the Au film are found to be in contact with the Si substrate from the scanning electron microscope image in slant view of 45°. The ReSe2/Si and Si/Au contacts are p-n heterojunction and Schottky contacts. Asymmetry of both contacts results in the rectification behavior. The prediction based on the thermionic emission theory agrees well with experimental data.

228 citations


Journal ArticleDOI
TL;DR: In this paper, the authors provide a review on Ga2O3-based optoelectronics, with a detailed introduction of the phosphors and EL devices and a concise summary of solar-blind photodetectors.

199 citations


Journal ArticleDOI
TL;DR: This work employs density functional theory calculations to show that van der Waals stacking can significantly modulate Schottky barrier heights in the contact formed between multilayer InSe and 2D metals by suppressing the FLP effect.
Abstract: Incorporation of two-dimensional (2D) materials in electronic devices inevitably involves contact with metals, and the nature of this contact (Ohmic and/or Schottky) can dramatically affect the electronic properties of the assembly. Controlling these properties to reliably form low-resistance Ohmic contact remains a great challenge due to the strong Fermi level pinning (FLP) effect at the interface. Herein, we employ density functional theory calculations to show that van der Waals stacking can significantly modulate Schottky barrier heights in the contact formed between multilayer InSe and 2D metals by suppressing the FLP effect. Importantly, the increase of InSe layer number induces a transition from Schottky to Ohmic contact, which is attributed to the decrease of the conduction band minimum and rise of the valence band maximum of InSe. Based on the computed tunneling and Schottky barriers, Cd3C2 is the most compatible electrode for 2D InSe among the materials studied. This work illustrates a straightforward method for developing more effective InSe-based 2D electronic nanodevices.

146 citations


Journal ArticleDOI
TL;DR: The eloquent evidences clearly prove that doping-adjusting the Fermi level has great potential applications in high-performance GaAs nanowire photodetectors and other functional photodETectors.
Abstract: 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.

145 citations


Journal ArticleDOI
TL;DR: In this article, a cube-like CeO2 and ultrathin Ti3C2-MXene nanosheets were used as a two-dimensional platform via a simple hydrothermal route for the development of efficient photocatalysts for environmental remediation.

124 citations


Journal ArticleDOI
01 Jan 2019
TL;DR: In this paper, thermal scanning probe lithography is used to pattern metal electrodes in direct contact with monolayer MoS2, creating field effect transistors that exhibit vanishing Schottky barrier heights, high on/off ratios of 1010, no hysteresis, and subthreshold swings as low as 64
Abstract: Two-dimensional semiconductors, such as molybdenum disulfide (MoS2), exhibit a variety of properties that could be useful in the development of novel electronic devices. However, nanopatterning metal electrodes on such atomic layers, which is typically achieved using electron beam lithography, is currently problematic, leading to non-ohmic contacts and high Schottky barriers. Here, we show that thermal scanning probe lithography can be used to pattern metal electrodes with high reproducibility, sub-10-nm resolution, and high throughput (105 μm2 h−1 per single probe). The approach, which offers simultaneous in situ imaging and patterning, does not require a vacuum, high energy, or charged beams, in contrast to electron beam lithography. Using this technique, we pattern metal electrodes in direct contact with monolayer MoS2 for top-gate and back-gate field-effect transistors. These devices exhibit vanishing Schottky barrier heights (around 0 meV), on/off ratios of 1010, no hysteresis, and subthreshold swings as low as 64 mV per decade without using negative capacitors or hetero-stacks. Thermal scanning probe lithography can be used to pattern metal electrodes in direct contact with monolayer MoS2, creating field-effect transistors that exhibit vanishing Schottky barrier heights, high on/off ratios of 1010, no hysteresis, and subthreshold swings as low as 64 mV per decade.

107 citations


Journal ArticleDOI
TL;DR: Improved sensitivity of a 2D MoS2-based gas sensor is demonstrated by controlling the Schottky barrier height and the NO2 responsivity increased, and it was found to be effective for CO and CO2 gases, which had little reactivity in 2DMoS2 -based gas sensors.
Abstract: Two-dimensional (2D) transition-metal dichalcogenides have attracted significant attention as gas-sensing materials owing to their superior responsivity at room temperature and their possible application as flexible electronic devices. Especially, reliable responsivity and selectivity for various environmentally harmful gases are the main requirements for the future chemiresistive-type gas sensor applications. In this study, we demonstrate improved sensitivity of a 2D MoS2-based gas sensor by controlling the Schottky barrier height. Chemical vapor deposition process was performed at low temperature to obtain layer-controlled 2D MoS2, and the NO2 gas responsivity was confirmed by the fabricated gas sensor. Then, the number of MoS2 layers was fixed and the types of electrode materials were varied for controlling the Schottky barrier height. As the Schottky barrier height increased, the NO2 responsivity increased, and it was found to be effective for CO and CO2 gases, which had little reactivity in 2D MoS2-b...

93 citations


Journal ArticleDOI
TL;DR: In this paper, a lateral β-Ga2O3 Schottky photodiode was fabricated on a sapphire substrate via magnetron sputtering using Ti and Ni as ohmic contacts, respectively.
Abstract: UV ray detection near the earth surface has become urgent due to the serious effects of UV rays on human health, the environment and the biological evolution; therefore, the development of energy-saving UV photodetectors with high responsivity, specific detectivity, and sensitivity is urgently desired. Herein, we fabricated a lateral β-Ga2O3 Schottky photodiode on a sapphire substrate via magnetron sputtering using Ti and Ni as ohmic and Schottky contacts, respectively. The photodiode shows rectifying behaviors in the dark and under 254/365 nm UV light illuminations. As a photodetector, it exhibits the high photo-to-dark current ratio of 2.83 × 105 owing to its low dark current (1.32 × 10−11 A) and strong UV absorbance. The responsivity at 250 nm could reach up to 144.46 A W−1 at 10 V. The external quantum efficiency of 64 711% and the ideal specific detectivity of 7.29 × 1014 cm Hz1/2 W−1 (Jones) were also achieved. The rejection ratio (R250 nm/R400 nm) was as high as 4.8 × 103, suggesting high wavelength selectivity. The responsivity of 2301.78 A W−1 at 180 V proves the ability of this photodetector to operate at high voltages. In addition, it can operate with the responsivity of 0.73 mA W−1 and the specific detectivity of 3.35 × 1010 cm Hz1/2 W−1 (Jones) at zero bias. Overall, the lateral Ti/β-Ga2O3/Ni structured Schottky photodiode was verified as an excellent candidate for UV solar-blind detection with high performance and low energy consumption.

80 citations


Journal ArticleDOI
TL;DR: In this paper, a high power 220 GHz frequency tripler based on a pair of GaN planar Schottky barrier diode chain chips was proposed. But the authors only considered the power consumption of the diodes.
Abstract: This letter presents our study on a high power 220 GHz frequency tripler based on a pair of GaN planar Schottky barrier diode chain chips. In the proposed frequency tripler, the pair of diode chips was directly mounted across the metal diaphragm in parallel with the opposite polarisation inside the rectangular waveguide. The RF field is tuned to its hot-spot, coupling directly onto the diode chains, turning on a diode chain at a time in an alternative manner. Unlike the traditional ones, in order to achieve better heat dissipation, the diodes are directly connected with the metal block. Benefitting from a better heat dissipation and the power endurance capacity of GaN material, the proposed tripler can work well under a watt level input power. The simulated tripler frequency conversion performance agrees with the measurement results very well. In addition, the experiments show that the frequency tripler can endure a maximum input power of 1.1W. In addition, the output power of this frequency tripler is 17.5mW at 219.5GHz driven by 900mW input power with the best efficiency of 1.93%.

80 citations


Journal ArticleDOI
TL;DR: In this paper, the authors implemented Mg implanted edge termination (ET), a simple but very useful technique to increase the breakdown voltage (BV) of the vertical $\beta $ -Ga2O3 Schottky barrier diode (SBD).
Abstract: This work reports on implementing Mg implanted Edge Termination (ET), a simple but very useful technique to increase the breakdown voltage (BV) of the vertical $\beta $ -Ga2O3 Schottky barrier diode (SBD). With this ET, vertical $\beta $ -Ga2O3 SBD demonstrates a reverse blocking voltage of 1.55 kV and low specific on-resistance ( ${R} _{ \mathrm{\scriptscriptstyle ON},\textrm {sp}}$ ) of 5.1 $\text{m}\Omega \cdot \textrm {cm}^{\textrm {2}}$ at a lightly doped $\beta $ -Ga2O3 layer with epitaxial thickness of $10~\mu \text{m}$ , yielding a high power figure-of-merit (P-FOM) of 0.47 GW/cm2. Combined with high forward current on/off ratio of 108 ~ 109, Schottky barrier height of 1.01 eV, and ideality factor of 1.05, vertical $\beta $ -Ga2O3 Schottky Diode with implanted ET verifies its great potential for future power rectifiers.

76 citations


Journal ArticleDOI
TL;DR: The Schottky surface barrier can overcome the large leakage current at a high electrical field, enabling us to reduce the noise and increase the charge collection efficiency.
Abstract: Hybrid methylammonium lead tribromide (MAPbBr3) perovskite has attracted great attention in ionization radiation detection. However, the charge collection remains a challenge. Here, fast response and high-sensitivity X-ray detection based on MAPbBr3 single crystals with a surface barrier Schottky diode has been achieved at room temperature. The Schottky surface barrier can overcome the large leakage current at a high electrical field, enabling us to reduce the noise and increase the charge collection efficiency. This surface barrier device has been demonstrated a 3 times improvement over the photoconductor based X-ray detector, which enables usage in nuclear medicine, especially for X-ray imaging technology.

Journal ArticleDOI
01 May 2019-Carbon
TL;DR: In this paper, the van der Waals (vdW) force is dominated by the interlayer interlayer spacing of 3.413 and binding energy per C atom of approximately 50 µmV.

Journal ArticleDOI
TL;DR: In this article, a low-power ZnO active-layered thin-film (60 nm) Schottky diode-one memristor device was fabricated and the material makeup of the device was confirmed via energy dispersive X-ray spectroscopy.
Abstract: Resistive random access memories (RRAMs) are favorable contenders in the race towards future technologies. Moreover, the desirable properties of memristor-based RRAM devices make them very good competitors in this field. The sneak paths problem poses one of the main difficulties in the construction of crossbar memory devices. This problem can be effectively suppressed by applying the 1diode-1resistor (1D1R) design structure. The Schottky diode has many advantages compared to the PN junction diode. The low-power (∼1 µW) ZnO active-layered thin-film (60 nm thick) one Schottky diode-one memristor device fabricated in this study included a top Ag electrode and a bottom Al electrode. The material makeup of the device was confirmed via energy dispersive X-ray spectroscopy (EDAX). The memristive and Schottky diode characteristics of the Ag/ZnO/Al device were resolved by measuring the time-dependent voltage/current. The characteristic pinched hysteresis memristive loops were observed at the first quadrant of the current-voltage plane, whereas the diode curves were seen at the third quadrant. Using the current-voltage curves, the height of the Schottky barrier, ideality factor and threshold voltage of the Schottky diode were found to be 0.68 eV, 3.75 and 0.49 V, respectively. After physical implementation and characterization of the one diode-one memristor device, its anti-crosstalk characteristics were investigated. Taking into account the 10% read margin, the maximum crossbar size was found to be 87.

Journal ArticleDOI
TL;DR: In this paper, a self-powered metal-semiconductor-metal (MSM) deep-ultraviolet (DUV) photodetector based on single crystal β-Ga2O3 was demonstrated.
Abstract: Self-powered photodetectors working in solar-blind region (below 280 nm) have attracted growing attention due to their wide applicability. Monoclinic Ga2O3 (β-Ga2O3) with excellent merits and a wide bandgap (4.9 eV) is regarded as a good candidate for solar-blind photodetector application. Self-powered photodetectors generally based on homo/heterojunction suffer from a complex fabrication process and slow photoresponse because of the interface defects and traps. Herein, we demonstrated a fabrication and characterization of a self-powered metal-semiconductor-metal (MSM) deep-ultraviolet (DUV) photodetector based on single crystal β-Ga2O3. The self-powered property was realized through a simple one-step deposition of an asymmetrical pair of Schottky interdigital contacts. The photocurrent and responsivity increase with the degenerating symmetrical contact. For the device with the most asymmetric interdigital contacts operated at 0 V bias, the maximum photocurrent reaches 2.7 nA. The responsivity Rλ, external quantum efficiency EQE, detectivity D*, and linear dynamic range LDR are 1.28 mA/W, 0.63, 1.77 × 1011 Jones, and 23.5 dB, respectively. The device exhibits excellent repeatability and stability at the same time. Besides, the device presents a fast response speed with a rise time of 0.03 s and a decay time of 0.08 s. All these results indicate a promising and simple method to fabricate a zero-powered DUV photodetector.

Journal ArticleDOI
TL;DR: In this paper, the authors reviewed recent progress on GaN-based vertical power Schottky barrier diode (SBD) including the following sections: the benchmark for GaN vertical SBDs with different substrates (Si, sapphire, and GaN) are presented, the latest progress in the edge terminal techniques are discussed.
Abstract: Gallium nitride (GaN)-based vertical power Schottky barrier diode (SBD) has demonstrated outstanding features in high-frequency and high-power applications. This paper reviews recent progress on GaN-based vertical power SBDs, including the following sections. First, the benchmark for GaN vertical SBDs with different substrates (Si, sapphire, and GaN) are presented. Then, the latest progress in the edge terminal techniques are discussed. Finally, a typical fabrication flow of vertical GaN SBDs is also illustrated briefly.

Journal ArticleDOI
Feng Yang1, Mingli Zheng1, Lei Zhao1, Junmeng Guo1, Bao Zhang1, Guangqin Gu1, Gang Cheng1, Zuliang Du1 
TL;DR: In this article, a surface-ionic-gate modulation technique was developed to modulate the surface states and Schottky barrier of nanowires, based on the gas discharge induced by triboelectric nanogenerators.

Journal ArticleDOI
TL;DR: In this article, a broadband spintronic diode was used for microwave detection in a magnetic tunnel junction, with a spintric diode providing sufficient dc voltage to supply a low-power nanodevice.
Abstract: A broadband spintronic diode would be important for electromagnetic energy harvesting, with the advantages of nanoscale size and low output resistance. This study gives experimental proof of broadband microwave detection in a magnetic tunnel junction, with a spintronic diode providing sufficient dc voltage to supply a low-power nanodevice. Such diodes also work as rectifiers below 1 nW, outperforming traditional Schottky diodes. These results point to spintronic diodes as building blocks in self-powered systems such as implantable biomedical devices, wireless sensors, and portable electronics, plus ultralow-power detectors for aerospace applications and the ``Internet of Things''.

Journal ArticleDOI
TL;DR: In this article, a lateral graphene/MoS2/graphene (GMG) heterostructure photodetector was synthesized by chemical vapor disposition (CVD) and electrical measurement showed that on/off ratio is up to 10 6 and two opposing Schottky junctions are connected in a series.

Journal ArticleDOI
TL;DR: In this paper, the formation of different Schottky barriers for Janus PtSSe and graphene based van der Waals heterostructures was investigated, and the authors found that the effects of tuning are more prominent for SPtSe/graphene as compared to SePtS/Graphene.
Abstract: Janus transition metal dichalcogenides with a built-in structural cross-plane asymmetry have recently emerged as a new class of two-dimensional materials with a large cross-plane dipole. By using the density functional theory calculation, we report the formation of different Schottky barriers for Janus PtSSe and graphene based van der Waals heterostructures, where the Schottky barrier height (SBH) and type of contact can be controlled by adjusting the interlayer distance, by applying an external electric field, and by having multiple layers of Janus PtSSe. It is found that the effects of tuning are more prominent for SPtSe/graphene as compared to SePtS/graphene. Besides, a transition from n-type Schottky contact to p-type Schottky contact and to Ohmic contact is also observed in the SPtSe/Gr heterostructure for different SPtSe stackings from 1 layer, to 2- and 3-layers, respectively. Our findings indicate that the SPtSe/graphene heterostructure is a suitable candidate for applications that require a tunable SBH.

Journal ArticleDOI
TL;DR: Fan et al. as discussed by the authors proposed an approach to boost the power conversion efficiencies (PCEs) of ferroelectric photovoltaics (PVs) based on the Schottky barrier effect.
Abstract: Achieving high power conversion efficiencies (PCEs) in ferroelectric photovoltaics (PVs) is a longstanding challenge. Although recently ferroelectric thick films, composite films, and bulk crystals have all been demonstrated to exhibit PCEs >1%, these systems still suffer from severe recombination because of the fundamentally low conductivities of ferroelectrics. Further improvement of PCEs may therefore rely on thickness reduction if the reduced recombination could overcompensate for the loss in light absorption. Here, a PCE of up to 2.49% (under 365-nm ultraviolet illumination) was demonstrated in a 12-nm Pb(Zr0.2Ti0.8)O3 (PZT) ultrathin film. The strategy to realize such a high PCE consists of reducing the film thickness to be comparable with the depletion width, which can simultaneously suppress recombination and lower the series resistance. The basis of our strategy lies in the fact that the PV effect originates from the interfacial Schottky barriers, which is revealed by measuring and modeling the thickness-dependent PV characteristics. In addition, the Schottky barrier parameters (particularly the depletion width) are evaluated by investigating the thickness-dependent ferroelectric, dielectric and conduction properties. Our study therefore provides an effective strategy to obtain high-efficiency ferroelectric PVs and demonstrates the great potential of ferroelectrics for use in ultrathin-film PV devices. An approach to boost the power conversion efficiencies (PCEs) of ferroelectric photovoltaics (PVs) is proposed based on the Schottky barrier effect. This approach leverages the thinning of a ferroelectric film to somewhere close to the depletion width, which can simultaneously suppress the recombination and lower the series resistance. Using this approach, we achieve a PCE up to 2.49% (under 365-nm ultraviolet illumination) in the 12-nm Pb(Zr0.2Ti0.8)O3 ultrathin films. Our study provides insightful guidance on how to design and tailor the ferroelectric films to achieve high PCEs, and also demonstrates the great potential of ferroelectrics for use in ultrathin-film PV devices. Eliminating stray electrical effects in ultra-thin films can help optimize an unconventional solar energy technology. Ferroelectric materials have internal dipoles that spontaneously move photogenerated charges toward external circuits, producing higher power outputs than predicted by theory. Zhen Fan from South China Normal University in Guangzhou and colleagues now report that the dimensions of ferroelectric thin films distinctly affect how efficiently they convert sunlight into electricity. Measurements of solar cells containing lead-zirconium-titanate ferroelectrics with different thicknesses revealed a jump in conversion efficiencies when the film reached a thickness of 12 nanometers. Further analysis showed that this thickness correlates with the solar cell’s ‘depletion width’, a zone formed when metal electrodes contact the film. The electric field in the depletion zone complements the pushing actions of the ferroelectric dipoles, lowering electrical losses compared to thicker ferroelectric films.

Journal ArticleDOI
TL;DR: In this paper, a specific contact pattern with interdigitated Schottky and graphene/insulator/silicon (GIS) structures is explored to experimentally demonstrate highly sensitive G/Si photodiodes.
Abstract: Graphene/silicon (G/Si) heterostructures have been studied extensively in the past years for applications such as photodiodes, photodetectors, and solar cells, with a growing focus on efficiency and performance. Here, a specific contact pattern scheme with interdigitated Schottky and graphene/insulator/silicon (GIS) structures is explored to experimentally demonstrate highly sensitive G/Si photodiodes. With the proposed design, an external quantum efficiency (EQE) of >80% is achieved for wavelengths ranging from 380 to 930 nm. A maximum EQE of 98% is observed at 850 nm, where the responsivity peaks to 635 mA/W, surpassing that of conventional Si p-n photodiodes. This efficiency is attributed to the highly effective collection of charge carriers photogenerated in Si under the GIS parts of the diodes. The experimental data is supported by numerical simulations of the diodes. On the basis of these results, a definition for the “true” active area in G/Si photodiodes is proposed, which may serve toward standar...

Journal ArticleDOI
TL;DR: In this paper, a fluorine-implanted termination (FIT) has been demonstrated in vertical GaN-on-GaN Schottky barrier diodes (SBDs).
Abstract: In this letter, fluorine-implanted termination (FIT) has been demonstrated in vertical GaN-on-GaN Schottky barrier diodes (SBDs). Owing to the unique feature of F ions that can become negative fixed charges in GaN, the electric field crowding at the junction edge can be mitigated and the breakdown voltage ( BV ) of the vertical GaN SBDs can be effectively enhanced. For SBDs, it is challenging to simultaneously achieve both high BV and low forward voltage drop ( ${V}_{{F}}$ ). Thanks to the effective leakage suppression by FIT, a high BV of ~800 V is realized in an FIT-SBD even with a low ${V}_{{F}}$ value of 0.85 V (at 100 A/cm2). By incorporating an AlGaN tunneling-enhancement layer, the FIT-SBD can achieve further improved BV of ~1020 V and ${V}_{{F}}$ of 0.83 V. Fast reverse recovery performance has also been realized in the FIT-SBDs.

Journal ArticleDOI
01 Nov 2019-Small
TL;DR: The introduction of the double-heterojunction design not only strengthens the light absorption of graphene/Si but also combines the advantages of the photogating effect and photovoltaic effect, which suppresses the dark current, accelerates the separation of photogenerated carriers, and brings photoconductive gain.
Abstract: Silicon-based electronic devices, especially graphene/Si photodetectors (Gr/Si PDs), have triggered tremendous attention due to their simple structure and flexible integration of the Schottky junction. However, due to the relatively poor light-matter interaction and mobility of silicon, these Gr/Si PDs typically suffer an inevitable compromise between photoresponsivity and response speed. Herein, a novel strategy for coupling 2D In2 S3 with Gr/Si PDs is demonstrated. The introduction of the double-heterojunction design not only strengthens the light absorption of graphene/Si but also combines the advantages of the photogating effect and photovoltaic effect, which suppresses the dark current, accelerates the separation of photogenerated carriers, and brings photoconductive gain. As a result, In2 S3 /graphene/Si devices present an ultrahigh photoresponsivity of 4.53 × 104 A W-1 and fast response speed less than 40 µs, simultaneously. These parameters are an order of magnitude higher than pristine Gr/Si PDs and among the best values compared with reported 2D materials/Si heterojunction PDs. Furthermore, the In2 S3 /graphene/Si PD expresses outstanding long-term stability, with negligible performance degradation even after 1 month in air or 1000 cycles of operation. These findings highlight a simple and novel strategy for constructing high-sensitivity and ultrafast Gr/Si PDs for further optoelectronic applications.

Journal ArticleDOI
TL;DR: In this paper, a high performance Pt/n−Ga2O3/n+Ga 2O3 solar blind Schottky photodiode has been grown by metalorganic chemical vapor deposition.
Abstract: We report on a high performance Pt/n−Ga2O3/n+Ga2O3 solar blind Schottky photodiode that has been grown by metalorganic chemical vapor deposition. The active area of the photodiode was fabricated using ∼30 A thick semi-transparent Pt that has up to 90% transparency to UV radiation with wavelengths < 260 nm. The fabricated photodiode exhibited Schottky characteristics with a turn-on voltage of ∼1 V and a rectification ratio of ∼108 at ±2 V and showed deep UV solar blind detection at 0 V. The Schottky photodiode exhibited good device characteristics such as an ideality factor of 1.23 and a breakdown voltage of ∼110 V. The spectral response showed a maximum absolute responsivity of 0.16 A/W at 222 nm at zero bias corresponding to an external quantum efficiency of ∼87.5%. The cutoff wavelength and the out of band rejection ratio of the devices were ∼260 nm and ∼104, respectively, showing a true solar blind operation with an excellent selectivity. The time response is in the millisecond range and has no long-time decay component which is common in photoconductive wide bandgap devices.We report on a high performance Pt/n−Ga2O3/n+Ga2O3 solar blind Schottky photodiode that has been grown by metalorganic chemical vapor deposition. The active area of the photodiode was fabricated using ∼30 A thick semi-transparent Pt that has up to 90% transparency to UV radiation with wavelengths < 260 nm. The fabricated photodiode exhibited Schottky characteristics with a turn-on voltage of ∼1 V and a rectification ratio of ∼108 at ±2 V and showed deep UV solar blind detection at 0 V. The Schottky photodiode exhibited good device characteristics such as an ideality factor of 1.23 and a breakdown voltage of ∼110 V. The spectral response showed a maximum absolute responsivity of 0.16 A/W at 222 nm at zero bias corresponding to an external quantum efficiency of ∼87.5%. The cutoff wavelength and the out of band rejection ratio of the devices were ∼260 nm and ∼104, respectively, showing a true solar blind operation with an excellent selectivity. The time response is in the millisecond range and has no long-ti...

Journal ArticleDOI
TL;DR: In this article, an analytical estimation method of turn on switching loss of a SiC mosfet and SiC Schottky barrier diode (SBD) pair from datasheet parameters and using values of common source and dc bus inductances is presented.
Abstract: Estimation of switching loss at the early stages of design is essential for determination of switching frequency and selection of power devices. Analytical estimation similar to gate charge method results in fastest and easiest computation when compared with simulation or double pulse test based experimental approach. This paper presents an analytical estimation method of turn on switching loss of a SiC mosfet and SiC Schottky barrier diode (SBD) pair from datasheet parameters and using values of common source and dc bus inductances. Turn on losses are considered as they dominate the total switching loss. The presented method models the quadratic nature of the transfer characteristics and results in better estimation of current rise time when compared with the linear approximation used in the literature. During voltage fall, the non-linear nature of the parasitic capacitances of both the switch and the diode are considered. The simulation and experimental results confirm the accuracy of the presented method over a range of operating conditions for two 1.2-kV discrete SiC mosfet and SBD pairs of different current ratings.

Journal ArticleDOI
TL;DR: The discovery of a dependence of the source barrier height on the semiconductor thickness and derivation of an analytical theory allow us to propose a design rule to achieve extremely high voltage gain, one of the most important figures of merit for a transistor.
Abstract: Despite being a fundamental electronic component for over 70 years, it is still possible to develop different transistor designs, including the addition of a diode-like Schottky source electrode to thin-film transistors. The discovery of a dependence of the source barrier height on the semiconductor thickness and derivation of an analytical theory allow us to propose a design rule to achieve extremely high voltage gain, one of the most important figures of merit for a transistor. Using an oxide semiconductor, an intrinsic gain of 29,000 was obtained, which is orders of magnitude higher than a conventional Si transistor. These same devices demonstrate almost total immunity to negative bias illumination temperature stress, the foremost bottleneck to using oxide semiconductors in major applications, such as display drivers. Furthermore, devices fabricated with channel lengths down to 360 nm display no obvious short-channel effects, another critical factor for high-density integrated circuits and display applications. Finally, although the channel material of conventional transistors must be a semiconductor, by demonstrating a high-performance transistor with a semimetal-like indium tin oxide channel, the range and versatility of materials have been significantly broadened.

Journal ArticleDOI
TL;DR: In this article, the carrier transport and gain mechanisms are exploited in the Ga2O3-based metal-semiconductor-metal photodetectors with Au back-to-back Schottky contacts.
Abstract: In this paper, carrier transport and gain mechanisms are exploited in the $\beta $ -Ga2O3-based metal–semiconductor–metal photodetectors with Au back-to-back Schottky contacts. The resultant devices exhibit a low dark current of $10^{{3}}$ , and a photo-to-dark current ratio of 50 at 473 K, indicative of its strong operation capability at high temperature and in harsh environments. Temperature-dependent current–voltage features reveal that the dark reverse leakage is dominated by the thermionic field emission at low electric field and Poole–Frenkel emission from a deep trap level of 0.42 eV under the conduction band at high field, respectively. These negatively charged traps positioned below the Fermi level in the vicinity of Schottky interface capture photogenerated holes and reduce the barrier height upon illumination. The temperature- and bias-dependent photoresponse features are identified in physics that the photoconductive gain as well as slow response speed is originated from the change of barrier height due to trap repopulation.

Journal ArticleDOI
06 Mar 2019
TL;DR: Enhanced splitting of water achieved by loading copper metal particles on mesoporous TiO2 microrods through involving of dual ligand agents into the reaction system is reported.
Abstract: Developing a highly efficient photocatalysis system based on a photocatalyst-cocatalyst host for the hydrogen evolution reaction has potential but is still challenging. Herein, we report enhanced splitting of water achieved by loading copper metal particles on mesoporous TiO2 microrods through involving of dual ligand agents into the reaction system. The composition, structure, and surface characteristics of the TiO2-Cu hybrid were analyzed by X-ray diffraction, X-ray photoelectron spectroscopy, scanning and transmission electron microscopy, and nitrogen adsorption. The formation of a Schottky contact in the interface between the Cu metal and the n-type semiconductor TiO2 was confirmed experimentally by photo/electrochemical measurements. This Schottky junction, the TiO2-Cu hybrid photocatalyst, exhibited superior hydrogen evolution capability with rate of 6046 μmol g−1 h−1, which is 23 times higher than that of pristine TiO2 (260 μmol g−1 h−1). The experimental results demonstrated that efficient separation and transfer of photo-induced electron-hole pairs greatly contributed to the enhanced photocatalytic H2 evolution. The Schottky contact between Cu and TiO2 as well as cocatalyst characteristic of Cu play significant roles in preventing the recombination of electron-hole pairs and enhancing water splitting to form hydrogen. This study demonstrates a rational design to construct Schottky contacts in metal-semiconductor junctions to significantly boost their photocatalytic capacity.

Proceedings ArticleDOI
01 Dec 2019
TL;DR: In this article, the authors report the first comprehensive research about GaN power integrated circuits (ICs) on GaN-on-SOI (silicon-oninsulator).
Abstract: We report the first comprehensive research about GaN power integrated circuits (ICs) on GaN-on-SOI (silicon-on-insulator). Specific stepped (Al)GaN superlattice buffer and highly robust deep trench isolation are developed. Various components including HEMT, metal-insulator-metal (MIM) capacitor, Schottky barrier diode (SBD), two-dimensional electron gas (2DEG) resistor, and resistor-transistor logic (RTL) are co-integrated, compatible with the p-GaN technology. Based on these achievements, 200 V GaN HEMT with integrated driver shows an extraordinary switching performance. A 48V-to-1V single-stage buck converter is realized using a GaN half-bridge with integrated on-chip drivers. Further, an all-GaN buck converter containing a smart control pulse-width modulation (PWM) circuit, dead-time control, drivers, and half-bridge is successfully designed using the GaN IC platform process design kit (PDK).

Journal ArticleDOI
TL;DR: In this article, the structure and mechanism of graphene/silicon solar cells are discussed and several key strategies to improve the performance of the cells are summarized, and the challenges and prospects of the devices are discussed in detail.
Abstract: Graphene has attracted tremendous interest due to its unique physical and chemical properties. The atomic thickness, high carrier mobility and transparency make graphene an ideal electrode material which can be applied to various optoelectronic devices such as solar cells, light-emitting diodes and photodetectors. In recent years, there has been a growing interest in developing graphene/silicon Schottky junction solar cells and the power conversion efficiency has reached up to 15.8% with an incredible speed. In this review, we introduce the structure and mechanism of graphene/silicon solar cells briefly, and then summarize several key strategies to improve the performance of the cells. Finally, the challenges and prospects of graphene/silicon solar cells are discussed in the development of the devices in detail.