Schottky Electrode Research Articles

High energy resolution CsPbBr3 alpha particle detector with a full-customized readout application specific integrated circuit

α particles must be monitored to be managed as radioactive diagnostic agents or nuclear activity indicators. The new generation of perovskite detectors suffer from limited energy resolution, which affects spectroscopy and imaging applications. Here, we report that the solution-grown CsPbBr3 crystal exhibits a low and stable dark current (34.6 nA·cm−2 at 200 V) by thinning the as-grown crystal to decrease the high concentration CsPb2Br5 phase near the surface. The introduction of the Schottky electrode for the CsPbBr3 detector further reduces the dark current and improves the high-temperature stability. An energy resolution of 6.9% is achieved with the commercial electronic system, while the effects of air scattering and absorption are investigated. Moreover, 1.1% energy resolution is recognized by a full-customized readout application-specific integrated circuit without any additional signal processing, which matches well with the given parameters of the CsPbBr3 detector by reducing the parasitic capacitance and electronic noise.

Epitaxial Growth of the Large-Scale, Highly-Ordered 3D GaN-Truncated Pyramid Array Toward an Ultrahigh Rejection Ratio and Responsivity Visible-Blind Ultraviolet Photodetection.

The micro- and nanostructures of III-nitride semiconductors captivate strong interest owing to their distinctive properties and myriad potential applications. Nevertheless, challenges endure in managing the damage inflicted on crystals through top-down processes or achieving extensive control over the large-area growth of these microstructures via bottom-up methods, thereby impacting their optical and electronic properties. Here, we present novel epitaxially grown 3D GaN truncated pyramid arrays (TPAs) on patterned Si substrates, devoid of any catalyst. These GaN TPAs feature highly ordered, large-scale structures, attributed to the utilization of 3D Si substrates and thin AlN interlayers to alleviate epitaxial strains and limit dislocation formation. Comprehensive characterization via scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and cathodoluminescence attests to the superior structural and optical attributes of these crystals. Furthermore, photoluminescence and ultraviolet (UV)-visible diffuse reflectance spectroscopy reveal sharp band-edge emission and significant light trapping in the UV bands. Employing these GaN TPAs, we constructed metal-semiconductor-metal visible-blind UV photodetectors (PDs) incorporating Ti3C2 MXene as Schottky electrodes. These PDs display exceptional responsivity, achieving 5.32 × 103 mA/W at 255 nm and an ultrahigh UV/visible rejection ratio (R255nm/R450nm) approaching 106, which are 1-2 orders of magnitude higher than most recently reported works. This exploration showcases novel GaN-based microstructures characterized by uniformity, ordered geometry, and exemplary crystalline integrity, paving the way for developing optoelectronic applications.

A 1.6 kV Ga2O3 Schottky Barrier Diode with a Low Reverse Current of 1.2 × 10-5 A/cm2 Enabled by Field Plates and N Ion-Implantation Edge Termination.

In this work, by employing field plate (FP) and N ion-implantation edge termination (NIET) structure, the electrical performance of the β-Ga2O3 Schottky barrier diode (SBD) was greatly improved. Ten samples of vertical SBDs were fabricated to investigate the influence of the relative positions of field plates (FPs) and ion implantation on the device performance. The device with the FP of 15 μm and the ion implantation at the edge of the Schottky electrode exhibited a breakdown voltage (Vbr) of 1616 V, a specific on-resistance (Ron,sp) of 5.11 mΩ·cm2, a power figure of merit (PFOM) of 0.511 GW/cm2, and a reverse current density of 1.2 × 10-5 A/cm2 @ -1000 V. Compared to the control device, although the Ron,sp increased by 1 mΩ·cm2, the Vbr of the device increased by 183% and the PFOM increased by 546.8%. Moreover, the reverse leakage current of the device with the FP and NIET structure decreased by three orders of magnitude. The TCAD simulation revealed that the peak electric field at the interface decreased from 7 MV/cm @ -500 V to 4.18 MV/cm @ -1000 V. These results demonstrate the great potential for the β-Ga2O3 SBD with a FP and NIET structure in power electronic applications.

Vertical diamond Schottky barrier diodes with curved field plates

Diamond Schottky barrier diodes (SBDs) could theoretically operate at high voltage, high temperature, and high frequency and be potentially used in power electronics. However, the device breaks down prematurely and cannot operate stably at high voltages due to the edge electric field crowding. In this work, a vertical diamond SBD with a curved field plate (CFP) was prepared using a chemical reflow method, inductively coupled plasma etching, and electron-beam evaporation. This structure alleviates the electric field crowding at the edge of the Schottky electrode and results in a breakdown voltage and current density of 380 V and over 3000 A/cm2, respectively. After repetitive measurements, we found that the device can repeatedly breakdown at around 380 V. These results indicate that CFP structure diamond SBDs have great application in high-voltage and high-power electronic devices.

Pt/GaN Schottky Barrier Height Lowering by Incorporated Hydrogen

Changes in the hydrogen-induced Schottky barrier height (Φ B) of Pt/GaN rectifiers fabricated on free-standing GaN substrates were investigated using current–voltage, capacitance–voltage, impedance spectroscopy, and current–time measurements. Ambient hydrogen lowered the Φ B and reduced the resistance of the semiconductor space–charge region while only weakly affecting the ideality factor, carrier concentration, and capacitance of the semiconductor space–charge region. The changes in the Φ B were reversible; specifically, the decrease in Φ B upon hydrogen exposure occurred quickly, but the recovery was slow. The results also showed that exposure to dry air and/or the application of a reverse bias to the Schottky electrodes accelerated the reversion compared with the case without the applied bias. The former case resulted in fast reversion because of the catalytic effect of Pt. The latter case, by contrast, suggested that hydrogen was incorporated into the Pt/GaN interface oxides as positive mobile charges. Moreover, both exposure to dry air and the application of a reverse bias increased the Φ B of an as-loaded sample from 0.91 to 1.07 eV, revealing that the Φ B of Pt/GaN rectifiers was kept lower as a result of hydrogen incorporation that likely occurred during device processing and/or storage.

Experimental analysis of the electric field distribution in semi-insulating GaAs detectors via alpha particles

Semi-insulating gallium arsenide (SI GaAs) detectors offer a promising alternative to commercially available silicon detectors. They demonstrate superior radiation hardness and provide improved efficiency for gamma and X-ray detection, primarily attributed to their higher density. In this study, we examined 350 μm thick SI GaAs detectors featuring front-side Ti/Pt/Au Schottky contacts with varying contact areas, complemented by back-side Ni/AuGe/Au ohmic contacts spanning the entire area. First, the reverse current-voltage characteristics of the prepared detectors were measured. The dependence of the reverse current and the breakdown voltage on the Schottky contact area was revealed. As the contact area decreases, the reverse current decreases and the breakdown voltage increases. The detection performance of the detectors was evaluated by alpha spectrometry using an 241Am source. After irradiation of the detectors from the Schottky electrode, the measured alpha spectra show an increasing CCE with decreasing Schottky contact area. Finally, the correlation between the applied bias voltage and the extent of the active detector area from the edge of the detector contact was investigated.

A 2.8 kV Breakdown Voltage α-Ga2O3 MOSFET with Hybrid Schottky Drain Contact.

Among various polymorphic phases of gallium oxide (Ga2O3), α-phase Ga2O3 has clear advantages such as its heteroepitaxial growth as well as wide bandgap, which is promising for use in power devices. In this work, we demonstrate α-Ga2O3 MOSFETs with hybrid Schottky drain (HSD) contact, comprising both Ohmic and Schottky electrode regions. In comparison with conventional Ohmic drain (OD) contact, a lower on-resistance (Ron) of 2.1 kΩ mm is achieved for variable channel lengths. Physics-based TCAD simulation is performed to validate the turn-on characteristics of the Schottky electrode region and the improved Ron. Electric-field analysis in the off-state is conducted for both the OD and HSD devices. Furthermore, a record breakdown voltage (BV) of 2.8 kV is achieved, which is superior to the 1.7 kV of the compared OD device. Our results show that the proposed HSD contact with a further optimized design can be a promising drain electrode scheme for α-Ga2O3 power MOSFETs.

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.

Ultrafast self-powered visible blind UV photodetectors based on MgZnO vertical Schottky junction in crossbar geometry

In order to achieve ultrafast response in MgZnO based self-powered Schottky type photodetectors, it is crucial to decrease both the junction capacitance and carrier transit time. To meet these criteria, Au/MgZnO/ITO Schottky junction photodetectors have been realised in crossbar pattern, wherein the thickness of the MgZnO thin film deposited on patterned ITO-glass substrate is ∼ 200 nm and the cross-sectional area of the devices is 0.032 mm2. The semi-transparent 10 nm Au electrode on top of the MgZnO film serves as the Schottky electrode through which light enters the devices. The vertical geometry of the crossbar pattern and the associated small device cross-section results in a low junction capacitance of the devices of ∼ 27 pF at zero bias, which in turn produces very fast visible blind self-powered ultraviolet (UV) photoresponse with both the rise and fall times of ∼ 1.5 μs, that is hitherto unreported for MgZnO based Schottky junction photodetectors. The devices also demonstrate a peak responsivity of ∼ 49 mA/W at ∼ 280 nm with a cut-off wavelength of 336 nm. These Au/MgZnO/ITO Schottky photodetectors in crossbar pattern, with optimized device area, could be useful in applications requiring fast response, such as UV communication and UV imaging.

Surface State Induced Filterless SWIR Narrow-Band Si Photodetector

In this letter, planar type self-powered short-wavelength infrared narrowband Si photodetector was realized based on a simple Schottky structure by increasing surface states and enlarging the distance between Schottky electrode and light irradiation region. With the assistance of pyramid microstructure, the distance needed for sub-100 nm narrowband detection effectively decreased from 1000 μ m to 200 μ m, which is vital to improving device sensitivity and reducing device size. The obtained photodetector exhibited a response peak at 1119 nm with full-width at half-maximum of 97 nm. At zero bias, a peak detectivity up to 2.25 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sup> Jones, linear dynamic range of 91 dB and fast response speed (Rise time of 88 μ s and fall time of 118 μ s) were achieved. The higher wavelength selectivity and sensitivity than its counterpart with flat surface should be ascribed to the large number of surface state and pronounced light confinement effect of pyramid microstructure. This work opens up a new avenue for achieving planar-type narrowband photodetector that can provide better integration capabilities for on-chip applications than vertical devices.

Filterless and High-Speed InP Near-Infrared Photodetector With an Ultra-Small Full-Width at Half Maximum

Near-infrared narrowband photodetection between 920 and 960 nm is quite appealing for many applications, such as optical communication, security monitoring, and machine vision, owing to the weak photon-scattering effect and the low intensity of sunlight in this range. Herein, a self-powered narrowband InP photodetector is realized based on a junction-controlled charge-collection narrowing (JCCN) mechanism, exhibiting a peak response centered at 954 nm with a full width at half maximum (FWHM) of 17 nm. Thanks to the reflection of the Schottky electrode and the passivation of the Al2O3 layer, the peak specific detectivity of the device can be up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4.5\times 10^{{11}}$ </tex-math></inline-formula> Jones and a linear dynamic range (LDR) of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim $ </tex-math></inline-formula> 99 dB is achieved under the illumination of 954 nm. Moreover, the device shows long-term stability and excellent repeatability with a −3 dB frequency of 87.3 kHz. Furthermore, unless the wavelength of the background light is in the range of 945–967 nm, the crosstalk value of the device remains below −10 dB. These results signify that the present InP photodetector is a promising building block for future near-infrared optoelectronic systems.

Lateral p-type GaN Schottky barrier diode with annealed Mg ohmic contact layer demonstrating ideal current–voltage characteristic

We have demonstrated the fabrication process for a lateral p-type Schottky barrier diode (SBD) with the annealed Mg ohmic contact layer on a MOVPE-grown p-GaN wafer and measured the electrical characteristic of the diode. Because of the selective-area ohmic contact, the interface between the Schottky electrode and p-type GaN is well protected from any damage introduced by dry-etching or regrowth. The ideality factor of the forward current–voltage characteristic is as low as 1.09 at room temperature and an on–off ratio above 109 is also achieved. Various metals are deposited as the Schottky electrode and the work function dependence of the Schottky barrier height is confirmed with a pinning factor of 0.58. The temperature dependence of the current–voltage characteristic indicates that the GaN p-type SBD still fits the thermionic emission mode at 600 K with an ideality factor of 1.1. The reverse current of the p-SBD is also studied with the Poole–Frenkel emission model, and the trap energy level in the p-GaN is confirmed.

The improvement of Schottky barrier diodes fabricated only by B ion implantation doping accomplished by refinement of the electrode structure

In this study, we fabricated p-type diamond Schottky barrier diodes (SBD) and performed selective B doping for the p-type channel and Ohmic region by double ion implantation. SBD were redesigned in the configuration and shape of Ohmic and Schottky electrodes to improve device characteristics. The fabricated device exhibited a rectification ratio of approximately 2400 because of decreasing the parasitic resistance to 2.7 × 107 Ω and the ideality factor to 2.7. The Schottky barrier height was obtained to be 1.04 eV. It is indicated that the diamond SBD fabricated only by B ion implantation is improved by refinement of the electrode structure.

Fabrication of Low-Threshold Discreet Schottky Barrier Diode Using Natural Pyrite Crystal

A low-threshold schottky barrier diode using natural pyrite has successfully been fabricated for the first time. The schottky and ohmic electrodes were successfully mounted and molded onto natural FeS2(pyrite) crystals. The I-V characteristics of the devices were measured, and the typical Schottky barrier diode characteristics were confirmed. The barrier height estimated by fitting was shown to be as low as 0.60 eV, indicating that the device has low-threshold characteristics.

ß-Ga2O3 flake based Schottky diode hydrogen sensor

2D (2-dimensional) (100) plane β phase Ga2O3 (β-Ga2O3) flake based Pt Schottky diode is demonstrated for hydrogen sensing application. The (100) plane β-Ga2O3 flake was formed from the side wall of a mother (2̅01) plane β-Ga2O3 bulk substrate by the cost-effective mechanical exfoliation method. The hydrogen response of the (100) plane Ga2O3 flake based diode with the catalytic Pt Schottky electrode for hydrogen decomposition reaction was measured in the wide concentration range of 50–40,000 ppm hydrogen. The β-Ga2O3 flake based hydrogen sensor showed excellent responsivity of 2.32 × 108% for the 500 ppm hydrogen exposure at 25°C, and exhibited a reliable hydrogen sensing behavior up to 400°C. The decent cross-selectivity of the (100) plane β-Ga2O3 flake based Pt Schottky diode sensor over the other gases including N2, CO, CO2, CH4, NO2, NH3, and O2 was observed. In addition, the effect of the humidity on hydrogen sensing was investigated.

High Breakdown Electric Field Diamond Schottky Barrier Diode With SnO2 Field Plate

Diamond is desirable for the application in power device due to its extremely high theoretical breakdown electric field (>10 MV/cm). However, because of electric field crowding, relatively low experimental results of breakdown electric field were attained. The vertical diamond with SnO2 field plate (FP) exhibiting excellent performance was fabricated. SnO2 deposited by electron beam evaporation with high dielectric constant of 17 possesses the potential to alleviate crowding field at the edge of Schottky electrodes. The SnO2 FP SBD shows high breakdown electric field of 4.04 MV/cm and high breakdown voltage of 185 V, which is 69.7% higher than diamond SBD without FP. The suppression of leakage current can also be observed in SBD with SnO2 FP. The edge electric field crowding of Schottky contact has been mitigated effectively by FP structure. Meanwhile, the FP SBD can still maintain low differential resistance of 1.31 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{m}\Omega \cdot \text {cm}^{{2}}$ </tex-math></inline-formula> , high forward current of 4740 A/cm2, unchanged Schottky barrier height, and ideality factor. It is suggested that SnO2 FP structure is a good method to improve reverse characteristics without compromising the forward performance of SBD, and this FP enables diamond SBD potential for power electronic devices.

Breakdown Voltage Enhancement of Vertical Diamond Schottky Barrier Diode With Annealing Method and AlO Field Plate Structure

We proposed a simple method to enhance the breakdown voltage (BV) and reduce the turn-on voltage (VON) for diamond vertical Schottky barrier diode (SBD) with Al2O3 field plate (FP) structure. The Al2O3 was deposited by atomic layer deposition at 200 °C. Ti/Pt/Au and Zr/Ni/Au metal stacks were used as ohmic and Schottky electrodes, respectively. Then, this FP terminated SBD was annealed at 400 °C to improve Al2O3 quality and lower Schottky barrier height. The ideality factor and Schottky barrier height are 1.60 and 1.42 eV, respectively. Compared with regular diamond SBD, the BV of annealed diamond SBD was enhanced from 162 V to 386 V with an increasement of 138%, and the VON was decreased from −2.30 to −1.65 V. This method is potential for the development of diamond power devices.

Improved-Performance Diamond Schottky Barrier Diode With Tin Oxide Interlayer

A SnO2 thin layer was deposited between the diamond and Schottky electrode to fabricate the metal–insulator–semiconductor Schottky barrier diode (MIS-SBD). The current–voltage and current–voltage–temperature characteristics in the range from 25 °C to 150 °C of diamond SBD were investigated. The Schottky barrier height of MIS-SBD is 1.84 eV. Compared with metal–semiconductor (MS) SBD, the diamond MIS-SBD shows more stable values of barrier height and ideality factor as temperature increased. The difference in interface states density between MIS-SBD and MS-SBD is almost 2 orders of magnitude, and the breakdown voltage was increased from 102 to 123 V after introducing SnO2 layer. These results indicate that the MIS-SBD with SnO2 insulating layer shows a better performance.

PERFORMANCE ANALYSIS OF PD/ZNO BASED FLEXIBLE UV MSM PHOTODETECTORS

Flexible electronics and optoelectronics devices attract further attention in recent years. In this paper, we present the fabrication and photodetection properties of a flexible metal-semiconductor-metal UV photodetector based on a thin ZnO film with Pd Schottky electrodes. The active ZnO layer was created using a hydrothermal method on ITO/PET flexible substrates. Palladium employed as back-to-back Schottky contacts. Metal masks are designed and used to deposit palladium via thermal evaporation. To demonstrate the impact of ZnO on flexible substrates, the structural, optical, and electrical characteristics of the produced films were examined and assessed. I-V characteristics under dark and illumination conditions for a device were measured using a voltage range of -2.8 V to 2.8 V. The measured data were used to calculate device parameters and photodetection properties. Such as ideality factor, barrier height, saturation current, detectivity, responsivity, contrast-ratio, and efficiency. The proposed device exhibited a gain (efficiency of 200%} caused by trapping hole carrier at the ZnO-Pd interface.

Self-powered electrolysis systems for sustainable hydrogen generation from natural seawater via a Ni/V2O3 Schottky electrode

Developing novel and efficient techniques for extracting hydrogen from natural seawater sustainably via electrolysis is highly attractive, yet remains a great challenge. Herein, a self-powered electrolysis system (SPES) driven by Mg/seawater batteries (MSBs) with a Ni/V2O3 Schottky electrode is demonstrated for sustainable production of hydrogen from seawater. The Ni/V2O3 Schottky electrode is constructed to serve as the hydrogen evolution reaction (HER) cathode for both the MSBs and seawater electrolysis unit in the SPES, enabling facile seawater HER with 10 and 1000 mA cm−2 at low overpotential of 176 and 649 mV respectively. The MSB with the Ni/V2O3 Schottky cathode delivers a peak power density up to 17.81 mW cm−2. Importantly, the designed SPES achieves a high hydrogen production rate up to 12.42 mL cm−2 h−1 from natural seawater with a high energy conversion efficiency of 80.87 %. This work offers an intriguing technique for in-situ sustainable acquisition of hydrogen from natural seawater.