Schottky Characteristics Research Articles

Asymptotic Behavior of the Generalized Schottky Anomaly and Characteristics of the Anomalies for Ferromagnet and Antiferromagnet

Asymptotic Behavior of the Generalized Schottky Anomaly and Characteristics of the Anomalies for Ferromagnet and Antiferromagnet

Study of surface over-layer contribution to Dislocation Assisted Tunneling current: Strategy to improve Pt/n+–GaN Schottky characteristics

This paper reports the importance of surface over-layer contribution to the dislocation assisted tunnelling (DAT) current along with earlier reported bulk dislocations due to growth of GaN layers on highly lattice-mismatched substrates. This claim is substantiated by demonstrating an improved Pt/n+–GaN Schottky diode characteristics with the removal of surface over-layer. This is achieved by treating the n+–GaN layers with Buffered Oxide Etchant (BOE) before Pt deposition. The improvements are observed in three crucial aspects of Pt/n+–GaN Schottky diode namely turn-on voltage (Vt); dislocation assisted tunnelling (DAT) parameter (E0), and reverse bias current. These improvements are achieved by treating n+–GaN surface with 1:7 BOE before Pt deposition. The DAT model adequately explains the device characteristics. Further, the dislocation density used in DAT analysis is experimentally quantified using HR-XRD. The removal of Ga2O3 and significant blue shift of Ga 3d peaks by 0.6 eV post-treatment as observed in XPS measurements, results in improved conduction of electrons at the n+–GaN surface and Pt/n+–GaN device characteristics.

Surface Effects of Passivation within Mo/4H-SiC Schottky Diodes through MOS Analysis

Passivation treatments applied prior to Mo metallisation on Silicon Carbide (SiC) Schottky rectifier and metal-oxide-semiconductor capacitor (MOSCAP) structures are studied. A control sample and two treatments, comprising of an O2 oxidation and a phosphorus pentoxide (P2O5) deposition, were studied. Electrical characterisation results show that P2O5 treatment improves the homogeneity of the diodes, with the ideality factor reducing to 1.02 and the leakage current reducing by three orders of magnitude to 2×10-5 A/cm2. Furthermore, the SBH was lowered by 0.11 eV and the variance of all the P2O5 treated Schottky characteristics over the batch reduced. Characterisation by X-ray photoelectron spectroscopy (XPS) showed that the stoichiometry, the Si:C ratio, of the SiC below the contact increased from 0.93:1 before treatment to 0.97:1 after P2O5 treatment.

Simple processed semi-transparent Schottky diode based on PMMA-MWCNTs nanocomposite for new generation of optoelectronics

• MWCNTs-PMMA/FTO semi-transparent Schottky diode is fabricated using convective self-assembly. • MWCNTs-PMMA exhibits UV and Visible light absorption. • A significant sensitivity of MWCNTs-PMMA/FTO diode to UV illumination intensity is evaluated. • The present architecture shows a good enhancement in the efficiency of the semi-transparent photodetectors. Herein, a semi-transparent Schottky diode based on poly (methyl methacrylate), PMMA, doped multiwall carbon nanotubes, MWCNTs/FTO is fabricated by a convective self-assembly method. The analyzed spectrophotometric optical transmittance profile of FTO/PMMA-MWCNTs/carbon device showed its maximum transparency of 62% at wavelength ˜ 472 nm. The values of direct as well as indirect energy gap are calculated by using absorption spectrum fitting (ASF) method and found to be in semiconducting range with values ˜ 3.21, and 2.78 eV, respectively. The estimated microelectronic parameters of FTO/PMMA-MWCNTs/carbon device has an ideality factor equal to one ( n = 1) and barrier height alters between 0.63 and 0.75 eV. The highest power conversion efficiency ( PCE ) that is achieved by the present architecture is about 5.64% at 12 mW/cm 2 . The fabricated FTO/PMMA-MWCNTs/carbon shows a Schottky and photovoltaic characteristics with semitransparency properties in the visible region.

Gaussian distribution of inhomogeneous barrier height in nanocrystalline graphite (NCG)/p-Si Schottky diodes

Schottky characteristics of nanocrystalline graphite/p-Si junction were investigated using current–voltage measurements at various temperatures between 298 and 473 K. Using the thermionic emission theory, the extracted ideality factor reduces by 77% while Schottky barrier height increases by 46% with increasing temperature. The initial obtained value of Richardson constant, A* from this device was 7.92 × 10−10 A cm−2 K−2. This value is far smaller than the theoretical value of 32 A cm−2 K−2 for p-Si which indicates inhomogeneity of a barrier height at the device interface. The Gaussian distribution plot was employed to explain the barrier height inhomogeneity, which gives the mean barrier height and standard deviation of 1.23 eV and 0.19 eV, respectively. By including the Gaussian distribution, the analysis of a modified Richardson plot gives a mean barrier height of 1.25 eV and a Richardson constant of 31.09 A cm−2 K−2, which are close to the theoretical values.

III-Nitride-based junction devices round contacts: effect of semiconductor film geometry and characteristics on the capacitance and conductance measurements

A theoretical model was developed, which allows simulating the capacitance (C) and conductance/frequency (G/f) profiles as a function of operation frequencies for a round Schottky diode, and in terms of a transfer length concept, LT(jω), which depends on the electrical characteristics of AlGaN:Si semiconductor film, dimensions and structure Schottky diode. The (C) and (G/f) measurements were performed by applying a small electrical signal far away and parallel to the planar structure of junction device, due to the impossibility of accessing perpendicularly path, since the AlGaN:Si semiconductor film was deposited over a substrate of high electrical resistivity, just as it happens with the III nitrates materials. The (C) and (G/f) profiles were measured for operating frequencies ranging from 3 kHz to 1 MHz. Comparison of experimental measurements and theoretical model were analyzed. It was found that the structure Schottky and electrical characteristics of film plays an important role as a limiting factor in the (C) and (G/f) measurements at media and high operating frequencies.

Investigation of the n-side structures of II-VI compound semiconductor optical devices on InP substrates

MgSe/ZnCdSe superlattices (SLs) and n-MgZnCdSe quaternaries were investigated as an n-cladding layer material of II-VI compound semiconductor optical devices on InP substrates. n-type samples consisting of n-doped ZnCdSe and n-MgSe/ZnCdSe SL or n-MgZnCdSe layers were fabricated on n-InP substrates by molecular beam epitaxy. From the injection current density versus applied voltage (J-V) characteristics of the samples, it was found that the applied voltage and resistivity of the MgZnCdSe sample were lower than those of the SL sample. This shows that MgZnCdSe is more suitable for the n-cladding layer. On the other hand, Schottky characteristics were observed for both samples, which were ascribed to conduction band hetero-barriers between the n-ZnCdSe and the SL or MgZnCdSe layers. The Schottky characteristics cause high applied voltages of the II-VI optical devices. To solve this problem (i.e., the Schottky characteristics), the incorporation of ZnCdSe/MgZnCdSe graded SLs at the interface between the n-ZnCdSe and MgZnCdSe layers was proposed. From the J-V characteristics, it was confirmed that the Schottky characteristics and applied voltages were reduced by introducing the graded SLs. This shows that the graded SLs are effective for lowering the applied voltages of II-VI optical devices on InP substrates.

Solar blind Schottky photodiode based on an MOCVD-grown homoepitaxial β-Ga2O3 thin film

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 Å 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.

Measure and analysis of 4H-SiC Schottky barrier height with Mo contacts

Current–voltage (I–V) and capacitance–voltage (C–V) characteristics of Schottky Mo/4H-SiC diodes have been measured and analyzed as a function of temperature between 80 and 400 K. The I–V characteristics significantly deviate from ideal characteristics predicted by the thermionic emission model because of the inhomogeneity of Schottky contact. After a brief review of the different existing models, the main parameters (ideality factor, barrier height, and effective Richardson constant) of both diodes have been extracted in the frame of a Gaussian barrier height distribution model, whose mean and standard deviation are linearly dependent on voltage and temperature, as well as in the context of the potential fluctuation model. The results are compared with the values extracted by C–V and the values in the literature. A link is established between these two models. Diodes of different I–V characteristics, either identified as single barrier or double barrier, have been analyzed by Deep Level Transient Spectroscopy (DLTS) to investigate the deep level defects present. No noticeable difference has been found.

Addressing the sneak-path problem in crossbar RRAM devices using memristor-based one Schottky diode-one resistor array

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.

The current-voltage characteristics of the ferroelectric p-YMnO3 thin film/bulk p-Si heterojunction over a broad measurement temperature range

The reverse and forward bias I-V characteristics of the Al/p-YMO/p-Si/Al heterojunction were measured at room temperature (RT) and over temperature range, from 50 to 320 K, and the I-V curves showed Schottky diode-like characteristics. The ideality factor and barrier height values were calculated as 0.81 and 2.62 from the forward bias I-V curve at room temperature (300 K), respectively. The YMO powder was prepared via solid state reaction technique. YMO thin films were grown on front surface of p-Si substrate by radio frequency (rf) magnetron sputtering using a polycrystalline YMO single target. The YMO thin film thickness on Si substrate was measured as ∼70 nm via Dektak XT surface profilometer. The XRD, SEM, UV–Vis and XPS measurements of the YMO thin film were also performed. The bandgap energy of YMnO3 thin films was determined as 2.10 eV by UV–vis. The temperature-dependent reverse and forward bias I-V curves were evaluated in terms of thermionic emission (TE), Schottky emission, Fowler-Nordheim (F-N) tunneling and space charge-limited current (SCLC) current theories. Furthermore, it has been seen that the forward bias conduction in the junction at each temperature obeys F-N tunneling because of the linearity in the ln (I/V2) versus V−1 curves.

Determination of the barrier height of Pt-Ir Schottky nano-contacts on Al-doped ZnO thin films by conductive Atomic Force Microscopy

By means of the I-V characteristics measured at room temperature, the height of the Schottky barrier established by the conductive Pt-Ir tip of an Atomic Force Microscope on the aluminum doped ZnO thin films were estimated in the range of 0.58-0.64 eV. The ideality factors were in the range of 2.11-1.39, respectively. These values are in accordance with those reported by other authors that measured the height of the Pt Schottky barrier on ZnO by means of several methods. The procedure detailed in this work suggests that the scanning time for obtaining I-V Schottky characteristics is of the order of 2 ms.

Temperature-dependent sensitivity in Pt/La2O3 nanobelt Schottky interface hydrogen sensors

Large surface area metal-oxide nanostructures enable substantially enhanced sensitivity for Schottky interface based hydrogen gas sensors. Although it is widely known that operating these gas sensors requires heating to an elevated temperature for optimal sensitivity, the fundamental mechanism that governs this temperature-dependent sensitivity has yet been well understood. In this work, we propose a technique based on thermionic field emission (TFE) theory for analyzing the transport characteristics of Schottky contacted nanostructured gas sensors. Through the fabrication and characterization of a Pt/La2O3 nanobelt Schottky contacted devices, we found the previously unreported correlation between TFE transport and optimal gas sensing temperature. This work augments our understanding of the sensitivity improvement from nanostructures in terms of carrier transport.

Effect of SiN:Hx passivation layer on the reverse gate leakage current in GaN HEMTs

This paper concentrates on the impact of SiN passivation layer deposited by plasma-enhanced chemical vapor deposition (PECVD) on the Schottky characteristics in GaN high electron mobility transistors (HEMTs). Three types of SiN layers with different deposition conditions were deposited on GaN HEMTs. Atomic force microscope (AFM), capacitance–voltage (C–V), and Fourier transform infrared (FTIR) measurement were used to analyze the surface morphology, the electrical characterization, and the chemical bonding of SiN thin films, respectively. The better surface morphology was achieved from the device with lower gate leakage current. The fixed positive charge Qf was extracted from C–V curves of Al/SiN/Si structures and quite different density of trap states (in the order of magnitude of 1011–1012 cm−2) was observed. It was found that the least trap states were in accordance with the lowest gate leakage current. Furthermore, the chemical bonds and the %H in Si–H and N–H were figured from FTIR measurement, demonstrating an increase in the density of Qf with the increasing %H in N–H. It reveals that the effect of SiN passivation can be improved in GaN-based HEMTs by modulating %H in Si–H and N–H, thus achieving a better Schottky characteristics.

Growth of Large‐Area SnS Films with Oriented 2D SnS Layers for Energy‐Efficient Broadband Optoelectronics

AbstractThe anisotropic properties of 2D orthorhombic SnS (tin monosulfide, p‐type) layers can be utilized in energy‐efficient optoelectronics by growing 2D SnS layers with a preferred orientation. To meet such a need, a strategy for growing SnS layers with the control of structural parameters such as orientation and thickness is highly desired. This report demonstrates a simple procedure for growing a large‐area SnS thin film composed of nanoscale SnS platelets with a controlled orientation relative to the surface via a single‐step process involving in situ sulfur depletion and phase structural transition of the sputter‐deposited SnS2 particles. The synthesized SnS films show good optoelectronic performances such as high signal‐to‐noise ratios, linear dynamic range, and high response speeds. In addition, the orientation of the SnS platelets is found to control the optoelectronic properties such as the electronic junction formation and the optical reflectance. The orientation‐controlled SnS layers on Si substrate operate as a good photosensor with a good zero‐bias photoresponse over a wide range of wavelengths including ultraviolet, visible, and near‐infrared. The device performances evaluated from the transient photovoltage, photocurrent, Mott–Schottky characteristics, and impedance spectroscopy are all well correlated with the geometric orientation of the 2D SnS layers within the film.

Resistive switching effect of YBa2Cu3O7–x/Nb:SrTiO3 heterostructure

In this study, YBa2Cu3O7―x/Nb:SrTiO3 (YBCO/Nb:STO) planar heterostructure was prepared on Nb:SrTiO3 (Nb:STO) substrate by sol-gel method. The I–V curves revealed that the structure exhibited excellent resistive switching (RS) effect. Current transmission characteristics of the heterostructure prepared using different electrodes and Nb:STO were analyzed. Results indicated that the RS effect was caused by the capture and escape of the electrons from the charge trap at the interface between electrode and Nb:STO. Schottky barrier was a prerequisite for the RS effect. Further investigation of the current transport properties of the YBCO/Nb:STO heterostructure at low temperature revealed that the current transport was affected by its own carriers and charge traps when the heterostructure was under low-resistance state, and the current decreased with decreasing temperature. Owing to the decrease in barrier height, the current increased with decreasing temperature under high-resistance state, with current transport properties exhibiting Schottky emission characteristics.

Yb3+-doped cadmium molybdato-tungstate single crystal – Its structural, optical, magnetic and transport properties

Single crystal of new cadmium and ytterbium molybdato-tungstate (Cd0.9706⎕0.0098Yb0.0196(MoO4)0.9706(WO4)0.0294, where ⎕ denotes cationic vacancies) has been successfully grown by the Czochralski method in air and under 1 MPa. X-ray crystallographic analysis reveals that the as-grown single crystal belongs to a scheelite-type structure (a = b = 5.15539(12) and c = 11.1919(3) Å, space group I41/a), in which Yb3+ ions do not show long-range order and are randomly distributed in the unit cell, substituting the Cd2+ ones. The as-grown single crystal does not show anisotropy of optical properties, i.e. its direct band gap reaches Eg = 1.76 or 1.75 eV along (100) and (001) crystallographic directions, respectively. The single crystal exhibits paramagnetic state with short-range antiferromagnetic and long-range ferrimagnetic interactions, a magnetization with zero coercivity and, a remanence that is almost a universal function of H/T, characterizing superparamagnetic-like behaviour. Electrical studies of the new ytterbium-doped cadmium molybdato-tungstate single crystal show a relatively small dielectric constant (εr<12), large lossiness of Joule-Lenz type observed at low frequencies as well as nonlinear I-V characteristics of Schottky or Maxwell-Wagner type.

Highly Stable Plasmon Induced Hot Hole Transfer into Silicon via a SrTiO3 Passivation Interface

AbstractExtracting plasmon‐induced hot carriers over a metal–semiconductor Schottky barrier enables photodetection below the semiconductor bandgap energy. However, interfacial carrier recombination hinders the efficiency and stability of this process, severely limiting its implementation in telecommunication. This study proposes and demonstrates the use of epitaxially grown lattice‐matched SrTiO3 for interfacial passivation of silicon‐based plasmonic Schottky devices. The devices are activated by an electrical soft‐breakdown of the interfacial SrTiO3 layer, resulting in reproducible rectified Schottky characteristics. The transition to a low resistance state of the SrTiO3 layer boosts the extraction efficiency of hot holes upon resonant plasmonic excitation, giving rise to a two orders of magnitude higher photocurrent compared to devices with a native oxide layer. Photoresponse, tunability, and barrier height studies under reverse biases as high as 100 V present superior stability with the incorporation of the SrTiO3 layer. The investigation paves the way toward plasmon‐induced photodetection for practical applications including those under challenging operating conditions.

Optical sensing performance characteristics of Schottky devices diodes based nano-particle disodium 6-hydroxy-5-[(2-methoxy-5-methyl-4-sulfophenyl)azo]-2-naphthalenesulfonate thin films: A comparison study

In the present work, nanocrystalline disodium 6-hydroxy-5-[(2-methoxy-5-methyl-4-sulfophenyl) azo]-2-naphthalenesulfonate (AR) thin films based devices were prepared by using electro-spin technique under best conditions. The nanostructure characteristics of the AR surfaces were found to be nanosphere-like structure by using scanning electron microscopy (SEM). The dark and 100 mW/cm2 illuminated current density–voltage (J–V) characteristics of the prepared heterojunctions by using different metal like Pt, Al and Cu were discussed at a temperature of 300 K. A diode-like behavior was obtained for all the studied devices and the rectification characteristics were obtained and compared. In addition, the arrangement protection and ideality factors demonstrated high interface reliance. Exposure of light on the AR dye / different metal structures produces a photocurrent which suggests the production of free carriers in all cases with different values which elucidate that these structures are promising for optoelectronic device applications.

Current transport mechanism of Schottky contact of Pt/Au/n-InGaN

The Pt/Au Schottky contacts to InGaN samples with different background carrier concentrations are fabricated. The crystal qualities of InGaN samples are characterized by X-ray diffraction (XRD) and atomic force microscope (AFM), and the correlation between threading dislocation density of InGaN and growth temperature is further clarified. The full width at half maximum (FWHM) values of the InGaN (0002) XRD rocking curves show that the density of threading dislocations in InGaN, which can seriously deteriorate InGaN crystal quality and surface morphology, decreases rapidly with increasing growth temperature. The Hall measurements show that the background carrier concentration of InGaN increases by two orders of magnitude as growth temperature decreases from 750 to 700℃, which is due to a reduced ammonia decomposition efficiency leading to the presence of high-density donor-type nitrogen vacancy (VN) defects at lower temperature. Therefore, combining the studies of XRD, AFM and Hall, it can be concluded that the higher growth temperature is favorable for realizing the InGaN film with low density of VN defects and threading dislocations for fabricating high-quality Schottky contacts, and then the barrier characteristics and current transport mechanism of Pt/Au/n-InGaN Schottky contact are investigated by current-voltage measurements and theory analysis based on the thermionic emission (TE) model and thermionic field emission (TFE) model. The results show that Schottky characteristics for InGaN with different carrier concentrations manifest obvious differences. It is noted that the high carrier concentration leads to the Schottky barrier height and the ideality factor obtained by TE model are quite different from that by TFE model due to the presence of high density of VN defects. This discrepancy suggests that the VN defects lead to the formation of the tunneling current and further reduced Schottky barrier height. Consequently, the presence of tunneling current results in the increasing of total transport current, which means that the defects-assisted tunneling transport and TE constitute the current transport mechanism in the Schottky. However, the fitted results obtained by TE and TFE models are almost identical for the InGaN with lower carrier concentration, indicating that TE is the dominant current transport mechanism. The above studies prove that the Pt/Au/n-InGaN Schottky contact fabricated using low background carrier concentration shows better Schottky characteristics. Thus, the properly designed growth parameters can effectively suppress defects-assisted tunneling transport, which is crucial to fabricating high-quality Schottky devices.