Properties Of Schottky Barrier Diodes Research Articles

Effect of annealing on the electrical performance of N-polarity GaN Schottky barrier diodes

A nitrogen-polarity (N-polarity) GaN-based high electron mobility transistor (HEMT) shows great potential for high-frequency solid-state power amplifier applications because its two-dimensional electron gas (2DEG) density and mobility are minimally affected by device scaling. However, the Schottky barrier height (SBH) of N-polarity GaN is low. This leads to a large gate leakage in N-polarity GaN-based HEMTs. In this work, we investigate the effect of annealing on the electrical characteristics of N-polarity GaN-based Schottky barrier diodes (SBDs) with Ni/Au electrodes. Our results show that the annealing time and temperature have a large influence on the electrical properties of N-polarity GaN SBDs. Compared to the N-polarity SBD without annealing, the SBH and rectification ratio at ±5 V of the SBD are increased from 0.51 eV and 30 to 0.77 eV and 7700, respectively, and the ideal factor of the SBD is decreased from 1.66 to 1.54 after an optimized annealing process. Our analysis results suggest that the improvement of the electrical properties of SBDs after annealing is mainly due to the reduction of the interface state density between Schottky contact metals and N-polarity GaN and the increase of barrier height for the electron emission from the trap state at low reverse bias.

Schottky barrier heights and electronic transport in Ga2O3 Schottky diodes

The Schottky contact, formed at the interface between a metal and a semiconductor, is instrumental in defining the electrical properties of Schottky barrier diodes (SBDs). The characteristics of the Schottky contact are contingent on the properties of interacting metal and semiconductor properties. Herein, we studied the carrier-transport mechanisms and electrical characteristics at room and elevated temperatures. These SBDs employ pre-treated Ga2O3 thin films and either Ni or Au Schottky contacts. The SBDs pre-treated (pre-T) via annealing at 900 °C under an N2 atmosphere for the Ni contact showed highest on/off ratio at room temperature. They also demonstrated ideality factors and Schottky barrier heights (SBHs) that remained relatively stable between 298 K and 523 K. To ascertain the SBH, ideality factors (n) derived from the thermionic emission (TE) and thermionic field emission (TFE) models were used, and results were subsequently compared. Moreover, SBDs employing Ni as the anode material exhibited lower SBHs than those employing Au. The pre-T Ni SBD was best described by the TFE model, wherein the SBH and ideality factor varied by 0.14 eV and 0.13, respectively, between 298 K and 523 K. Conversely, for pre-T Au, untreated Ni, and untreated Au SBDs, neither TE and TFE provided a satisfactory fit due to the ideality factor is greater than 2 at room temperature and the variation of SBH and n with temperature. These suggests that the transport mechanism should be described by other physical mechanisms. Without pre-treatment, both the Ni and Au SBDs exhibited more significant variation in the SBH and n with temperature. SBHs values were determined using measurement of current, capacitance and x-ray photoelectron spectroscopy, and were found to depend on the interface quality, indicating inhomogeneous SBH. Our results suggest that the use of annealing pre-treatments and anode metals with low work functions holds considerable potential for reducing Schottky barrier heights in Schottky diodes, thereby enhancing their electrical performance.

Temperature-dependent electrical properties of schottky barrier diodes based on carbon nanotube arrays

Temperature-dependent electrical properties of schottky barrier diodes based on carbon nanotube arrays

A Study on the Wide Frequency Range Electrical Variables in the Al/Coumarin–PVA/p-Si Diodes at Room Temperature

Coumarin-PVA is deposited onto p-Si wafers using the spin coating technique. I examined the fundamental electrical variables of the Al/CoumarinPVA/p-Si type Schottky barrier diodes (SBDs), by utilizing capacitance/voltage(C-V) and conductance/voltage (G-V) measurements at different frequencies varied from 10kHz to1MHz. I have thoroughly explored how the CoumarinPVA interlayer, series resistance (Rs) and surface states (Nss) affect the electrical properties of SBDs. In order to remove Rs's influence on the observed C and G values, I corrected them. The observed high values of C/G measured at low frequencies result from the existence of interfacial states. There is evidence that while NA decreases exponentially with increasing frequency, B increases exponentially. A particular distribution of Nss density, polarization processes, and the existence of an interfacial layer can all contribute to explaining these characteristic features of them. According to experimental findings, I conclude that the interfacial polymer CoumarinPVA layer as well as the Nss and Rs also have a significant impact on the C/G-V quantities of SBDs.

Pt/ZnGa₂O₄ Schottky Barrier Diodes Fabricated by Using Single Crystal n-ZnGa₂O₄ (111) Substrates

In this letter, we fabricated Schottky barrier diodes (SBDs) using n-type zinc gallium oxide (n-ZnGa2O4) single-crystal substrates, which were grown from the melt by the vertical gradient freeze (VGF) method. X-ray diffraction rocking curve and Laue diffraction results indicate the good crystal quality. The electrical properties of SBDs fabricated on substrates with two doping concentrations are systematically investigated. Heavily-doped (HD) SBDs exhibit lower differential specific on-resistance (~1.13 <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 $ </tex-math></inline-formula> cm2) and lower turn-on voltage (~0.16 V) while the lightly-doped (LD) SBDs exhibit better ideality factor (1.17), rectification characteristics (on/off ratio ~1011) and lower reverse leakage. In addition, we separately tested the electrical properties of the two devices at different temperatures (298 K-473 K). The results of varying temperature show that LD-SBDs have better temperature stability in smaller variation of ideality factor and barrier height with temperature. Based on these experimental results, this work demonstrates the great promise of ZnGa2O4 materials to fabricate high-performance power devices.

Parameter Estimation of AI/p-Si Schottky Barrier Diode Using Different Meta-Heuristic Optimization Techniques

Schottky barrier diodes (SBD) are crucial in the electronics sector. The electronic properties of SBD are characterized by three basic electrical parameters as the ideality factor (n), barrier height (ΦSB) and series resistance (RS). These parameters are significant in designing and producing SBD. This paper presents a comprehensive review of metaheuristic optimization techniques used to determine the fundamental electrical parameters of SBD using experimental forward current–voltage (I-V) characteristics. In the study, popular meta-heuristic optimization techniques, such as GA, PSO, ALO, EO, DA, HHO, GWO, WOA, MFO, MVO, and SCA algorithms, are employed for the parameter estimation of SBD. Among these chosen algorithms, meta-heuristic optimization techniques, such as GWO, WOA, HHO and AHA, have been used for the first time in the literature for parameter estimation of SBD. Firstly, parameter values have been calculated using experimental (I-V) characteristics. Following that, the findings were compared to the values that had been estimated utilizing optimization techniques. Moreover, the performance of meta-heuristic optimization algorithms in determining the basic parameters of SBD was evaluated statistically. Results show that AHA has higher and symmetrical estimation performance than other presented algorithms in determining the basic parameters of SBD with R2 = 0.999925806, MAE = 2.79065 × 10−7, RMSE = 7.49521 × 10−7, RE = 0.422088668, and STD = 7.68031 × 10−7 statistical values.

Diamond Schottky barrier diodes fabricated on sapphire-based freestanding heteroepitaxial diamond substrate

In this study, diamond Schottky barrier diodes (SBDs) fabricated on a sapphire-based heteroepitaxial diamond substrate were demonstrated. For commercializing diamond-based power electronics, a large-sized heteroepitaxial diamond substrate is essential. Sapphire is one of the most promising candidates among the diamond heteroepitaxial substrates because it can be produced on a large scale and its thermal expansion coefficient is similar to that of diamond, compared to that of any other non-diamond hetero substrate. The current-voltage characteristics of heteroepitaxial diamond SBDs grown under different growth rates were analyzed, and good rectification properties of SBDs were observed at the device grown with low growth rate. The ideality factor was 1.4, and the maximum breakdown field was approximately 1.1 MV/cm. The value of built-in potential derived from the capacitance-voltage characteristics was in good agreement with the approximated barrier heights. Some ball-shaped features on the SBD along the threading dislocation were directly observed after performing the breakdown test under reverse bias condition using transmission electron microscope (TEM). Threading dislocation which induces breakdown or large leakage current under reverse bias in diamond SBD was clarified and this will lead the research direction of a heteroepitaxial diamond electronic device. Prime novelty statementsRecently, the diamond SBD grown on large-size heteroepitaxial diamond substrates becoming alternative to conventional high temperature high pressure (HPHT) diamond-based diamond SBD. In this study, diamond SBD grown on sapphire-based freestanding heteroepitaxial diamond substrate was successfully demonstrated. The sapphire substrate is one of the most promising material as substrate for heteroepitaxial diamond which is low cost and large sized. The heteroepitaxial diamond SBD structures with different growth rate were grown using microwave plasma CVD (MPCVD) and its structural properties were characterized. After device fabrication process, the detailed analysis of electrical properties of SBD were carried out. The direct observation of breakdown and leakage current features on SBD was obtained before and after electrical test under reverse bias condition.

Surface states on (001) oriented β -Ga2O3 epilayers, their origin, and their effect on the electrical properties of Schottky barrier diodes

Surface states on (001) oriented halide vapor phase epitaxy (HVPE) grown β-Ga2O3 epilayers were explored through the determination of the Schottky barrier height (SBH) as a function of the metal work function using Cr, Cu, Ni, and Au Schottky barrier diodes. SBH is found to be nearly pinned between 1.2 and 1.35 eV in the HVPE grown epilayers. The position of the Fermi level pinning is closely matched with the energy level of the oxygen vacancy [VO(III)] state (EV + 3.57 eV) in the energy bandgap of β-Ga2O3, indicating that Fermi level pinning is due to oxygen vacancy type surface states on (001) oriented β-Ga2O3 epitaxial layers. The Fermi level is found to be relatively unpinned on the bulk β-Ga2O3 (001) substrate, suggesting the presence of lower density of oxygen vacancy states on its surface. Hence, the HVPE growth process was found to be responsible for the presence of oxygen vacancy states [VO(III)] in the epilayer. Moreover, this work highlights the role of these surface states in determining the SBH on β-Ga2O3 (001) epilayers and also explains the reason behind the scattered data of SBH values reported in the literature. In addition to these results, we also showed an increment in the built-in potential and the reduction of reverse leakage current for the epilayer with lower surface state density, which gives a direct evidence of the effect of surface states on the properties of β-Ga2O3 (001) Schottky barrier diodes.

Electrical Properties of Top-Gate β-Ga₂O₃ Nanomembrane Metal-Semiconductor Field-Effect Transistor.

We fabricate top-gate β-Ga₂O₃ nanomembrane metal-semiconductor field-effect transistor (MESFET) using a mechanical exfoliation method, and investigate its electrical performance. The Schottky contact between top-gate metal and β-Ga₂O₃ (100) channel is evaluated by characterizing properties of Schottky barrier diode, exhibiting an on/off ratio of ~106, an ideality factor of 2.8 and a turn-on voltage of 1.1 V. The proposed top-gate β-Ga₂O₃ nanomembrane MESFET exhibits maximum transconductance of ~0.23 mS/mm, field-effect mobility of 1.2 cm²/V·s at VDS = 1 V and subthreshold slope (SS) of 180 mV/dec with high on/off ratio of >107. These results suggest that β-Ga₂O₃ nanomembrane MESFET could be a promising component toward β-Ga₂O₃-based high power device applications.

Insight Into Ni/4H-SiC Schottky Barrier Inhomogeneity at Microscale Level

Ni/4H-SiC Schottky barrier diodes (SBDs) are fabricated and then annealed at different annealing temperatures to explore the Schottky barrier inhomogeneity (SBI). The macro- and microelectrical properties of SBDs are characterized by current–voltage ( ${I}$ – ${V}$ ) curves and using a conductive atomic force microscope (CAFM), respectively. The morphologies of the contact surface and the interface are observed using a scanning electron microscope (SEM) and an atomic force microscope (AFM), respectively. The results show that the annealed SBDs exhibit double-barrier characteristics, which come up with two distinct explanations for the observed SBI at different annealing temperatures. The formation of voids in the contact layer and the hexagonal pits in the SiC leads to the SBI in 600 °C-annealed SBDs. As for the 400 °C- and 500 °C-annealed SBDs, only the formation of voids in the contact layer matters. Schottky barriers on the pit (voids) areas are lower (higher) than that on other areas. The established relationship among the annealing temperatures, morphologies, and microelectrical properties deepens the understanding of the barrier inhomogeneity and provides a direction for improving the Schottky barrier homogeneity.

Large reduction of threading dislocations in diamond by hot-filament chemical vapor deposition accompanying W incorporations

Dislocations in semiconductor crystals are desirably minimized as much as possible, since their presence typically deteriorates device performance. While diamond electronics have demonstrated superior device properties, they have not fulfilled their material limit yet. To further improve device performance, a low dislocation density and a high-quality epitaxial layer are required. In this study, diamond films are homoepitaxially grown by hot-filament chemical vapor deposition accompanying W incorporations from heated metal-wires. The films exhibited better crystalline quality than seed substrates: a large reduction of threading dislocation from 2 × 106 to 3 × 104 cm−2 was demonstrated. The dislocation propagation was partially annihilated by W impurities. The electrical properties of Schottky barrier diodes after dislocation reduction were highly uniform, improved rectifying actions.

Electrical properties of Schottky barrier diodes fabricated on (001) β-Ga2O3 substrates with crystal defects

The electrical properties of Schottky barrier diodes (SBDs) on a (001) β-Ga2O3 substrate were characterized and correlated with wet etching-revealed crystal defects below the corresponding Schottky contacts. The etching process revealed etched grooves and etched pits, indicating the presence of line-shaped voids and small defects near the surface, respectively. The electrical properties (i.e., leakage currents, ideality factor, and barrier height) exhibited almost no correlation with the density of the line-shaped voids. This very weak correlation was reasonable considering the parallel positional relation between the line-shaped voids extending along the [010] direction and the (001) basal plane in which the voids are rarely exposed on the initial surface in contact with the Schottky metals. The distribution of small defects and SBDs with unusually large leakage currents showed similar patterns on the substrate, suggesting that these defects were responsible for the onset of fatal leak paths. These results will encourage studies on crystal defect management of (001) β-Ga2O3 substrates for the fabrication of devices with enhanced performance using these substrates.

Frequency dependent C–V and G/ω–V characteristics on the illumination-induced Au/ZnO/n-GaAs Schottky barrier diodes

Au/ZnO/n-GaAs Schottky barrier diodes (SBDs) have been examined by the capacitance–voltage (C–V) and conductance–voltage (G/ω–V) measurements. The frequency dependence characteristics of measurements were obtained under various illumination levels at room temperature. The C and G/ω relation was observed as the decrement in capacitance corresponds to an increment in conductance. The increment of negative capacitance (NC) values by high frequency at forward biases was ascribed to the series resistance, interface states and interfacial layer. Considering the illumination intensity, the NC values were observed to increase with the decreasing illumination while the G/ω values increase with the increasing illumination. This behavior was referred to the increments in the polarization and carriers in the SBDs. The adverse impacts of the voltage dependent resistivity were decreased with increasing illumination levels. Eventually, a strong interaction between the electrical properties of SBDs and the frequency, illumination and applied bias voltage was demonstrated by experimental results.

Structure of Straight-Line Defect and its Effect on the Electrical Properties of Schottky Barrier Diodes

We have investigated the “straight-line defect,” which has not been classified separately and is quite similar to the carrot defect. We found that the straight-line defect differed structurally from the carrot defect. The presence of a particle on the substrate-epi layer interface seemed to be the cause of the defect; a layer of poly-type (3C-SiC) extended from the particle to the epi-layer surface. The straight-line defect likely resulted from shape change from the 3C-SiC triangular defect. This change in shape from triangular to straight-line defects depended on the C/Si ratio. To investigate the electrical characteristics, we fabricated a Schottky barrier diode (SBD) structure on a silicon carbide (SiC) epi wafer. With application of a high voltage, destruction occurred on both the upstream and the downstream side of the step flow of straight-line defects in the reverse voltage test. This reverse direction characteristic differed from that observed with triangular defects.

Investigation on dielectric properties of atomic layer deposited Al2O3 dielectric films

Al/Al2O3/p-Si Schottky barrier diodes (SBDs) were fabricated using atomic layer deposition technique in order to investigate dielectric properties of SBDs. For this purpose, admittance measurements were conducted at room temperature between −1 V and 3 V in the frequency range of 10 kHz and 1 MHz. In addition to the investigation of Al2O3 morphology using atomic force microscope, dielectric parameters; such as dielectric constant (ε′), dielectric loss (ε″), dielectric loss tangent (tan δ), and real and imaginary parts of dielectric modulus (M′ and M″, respectively), were calculated and effect of frequency on these parameters of Al/Al2O3/p-Si SBDs was discussed. Variations in these parameters at low frequencies were associated with the effect of interface states in low frequency region. Besides dielectric parameters, ac electrical conductivity of these SBDs was also investigated.

Investigations of Current Mechanisms and Electronic Properties of Schottky Barrier Diode

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극성/무극성 6H-SiC 쇼트키 베리어 다이오드 제조 및 전기적 특성 연구

We have fabricated schottky barrier diode (SBDs) using polar (c-plane) and non polar (a-, m-plane) n-type 6H-SiC wafers. Ni/SiC ohmic contact was accomplished on the backside of the SiC wafers by thermal evaporation and annealed for 20minutes at <TEX>$950^{\circ}C$</TEX> in mixture gas (<TEX>$N_2$</TEX> 90% + <TEX>$H_2$</TEX> balanced). The specific contact resistance was <TEX>$3.6{\times}10^{-4}{\Omega}cm^2$</TEX> after annealing at <TEX>$950^{\circ}C$</TEX>. The XRD results of the alloyed contact layer show that formation of <TEX>$NiSi_2$</TEX> layer might be responsible for the ohmic contact. The active rectifying electrode was formed by the same thermal evaporation of Ni thin film on topside of the SiC wafers and annealed for 5 minutes at <TEX>$500^{\circ}C$</TEX> in mixture gas (<TEX>$N_2$</TEX> 90% + <TEX>$H_2$</TEX> balanced). The electrical properties of SBDs have been characterized by means of I-V and C-V curves. The forward voltage drop is about 0.95 V, 0.8 V and 0.8 V for c-, a- and m-plane SiC SBDs respectively. The ideality factor (<TEX>${\eta}$</TEX>) of all SBDs have been calculated from log(I)-V plot. The values of ideality factor were 1.46, 1.46 and 1.61 for c-, a- and m-plane SiC SBDs, respectively. The schottky barrier height (SBH) of all SBDs have been calculated from C-V curve. The values of SBH were 1.37 eV, 1.09 eV and 1.02 eV for c-, a- and m-plane SiC SBDs, respectively.

Effect of hydroquinone on the electrical properties of dodecylbenzene sulfonic acid doped polypyrrole/aluminum Schottky junction

Electrical properties of Schottky barrier diode fabricated using Aluminum for Schottky contact and indium tin oxide for ohmic contact and containing polypyrrole doped with dodecylbenzene sulfonic acid in the presence and in the absence of a plasticizing agent hydroquinone were studied. Various parameters, e.g. saturation current, ideality factor, built in voltage; carrier concentration and barrier height have been calculated and found to be affected by the presence of hydroquinone in the doped polymer. The electrical behavior of the systems was found to be in a good agreement with the thermionic emission model for the Schottky barrier devices. The interaction of the doped polypyrrole with hydroquinone was explained in terms of change in the barrier height and in the carrier concentration of the diodes.

Shot-noise suppression in Schottky barrier diodes

We give a theoretical interpretation of the noise properties of Schottky barrier diodes based on the role played by the long range Coulomb interaction. We show that at low bias Schottky diodes display shot noise because the presence of the depletion layer makes the effects of the Coulomb interaction negligible on the current fluctuations. When the device passes from barrier to flat band conditions, the Coulomb interaction becomes active, thus introducing correlation between different current fluctuations. Therefore, the crossover between shot and thermal noise represents the suppression due to long range Coulomb interaction of the otherwise full shot noise. Similar ideas can be used to interpret the noise properties of other semiconductor devices.

Effects of the epitaxial layer thickness on the noise properties of Schottky barrier diodes

An analytical theory to describe the combined effects of the epitaxial layer thickness and the ohmic contact on the noise properties of Schottky barrier diodes is presented. The theory, which provides information on both the local and the global noise properties, takes into account the finite size of the epitaxial layer and the effects of the back ohmic contact, and applies to the whole range of applied bias. It is shown that by scaling down the epitaxial layer thickness, the current regime in which the noise temperature displays a shot-noise-like behavior increases at the cost of reducing the current range in which the thermal-noise-like behavior dominates. This improvement in noise temperature is limited by the effects of the ohmic contact, which appear for large currents. The theory is formulated on general trends, allowing its application to the noise analysis of other semiconductor devices operating under strongly inhomogeneous distributions of the electric field and charge concentrations.