Effective Schottky Barrier Height Research Articles

Asymmetric Metal/α-In2Se3/Si Crossbar Ferroelectric Semiconductor Junction.

A ferroelectric semiconductor junction is a promising two-terminal ferroelectric device for nonvolatile memory and neuromorphic computing applications. In this work, we propose and report the experimental demonstration of asymmetric metal/α-In2Se3/Si crossbar ferroelectric semiconductor junctions (c-FSJs). The depletion in doped Si is used to enhance the modulation of the effective Schottky barrier height through the ferroelectric polarization. A high-performance α-In2Se3 c-FSJ is achieved with a high on/off ratio > 104 at room temperature, on/off ratio > 103 at an elevated temperature of 140 °C, retention > 104 s, and endurance > 106 cycles. The on/off ratio of the α-In2Se3 asymmetric FSJs can be further enhanced to >108 by introducing a metal/α-In2Se3/insulator/metal structure.

Experimental Investigation of As Preamorphization Implant on Electrical Property of Ti-Based Silicide Contacts

The impact of As preamorphization implant (PAI) on specific contact resistivity ( ρ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ) is investigated for Ti-based Ohmic contacts on n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -Si in this article. The ρ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> value of TiSi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> /n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -Si contacts is greatly improved with low-dose As PAI whereas this improvement is impaired with increased dose of As PAI. The ρ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> results from the joint effort of the reduction of effective Schottky barrier height (SBH) to electrons ( φ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\text bn,eff</sub> ), retardation of Ti silicidation, and annihilation of end-of-range (EOR) defects. Besides, the interfacial microstructures of TiSi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> /n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -Si affect ρ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> , correlated with the post metal anneal (PMA).

Electronic Control of Hot Electron Transport Using Modified Schottky Barriers in Metal-Semiconductor Nanodiodes.

Hot electron flux, generated by both incident light energy and the heat of the catalytic reaction, is a major element for energy conversion at the surface. Controlling hot electron flux in a reversible manner is extremely important for achieving high energy conversion efficiency. Here we demonstrate that hot electron flux can be controlled by tuning the Schottky barrier height. This phenomenon was monitored by using a Schottky nanodiode composed of a metal-semiconductor. The formation of a Schottky barrier at a nanometer scale inevitably accompanies an intrinsic image potential between the metal-semiconductor junction, which lowers the effective Schottky barrier height. When a reverse bias is applied to the nanodiode, an additional image potential participates in a secondary barrier lowering, leading to the increased hot electron flow. Besides, a decrease of tunneling width results in facile electron transport through the barrier. The increased hot electron flux by the chemical reaction (chemicurrent) and by the photon absorption (photocurrent) indicates hot electrons are captured more effectively by modifying the Schottky barrier. This study can shed light on a quantitative understanding and application of charge behavior at metal-semiconductor interfaces, in solar energy conversion, or in a catalytic reaction.

Heavy ion radiation and temperature effects on SiC schottky barrier diode

The function of a commercial Schottky Barrier Diode (SBD) based on 4H-SiC in an environment of extreme temperature and radiation was assessed. The capacitance-voltage (C-V) and current-voltage (I-V) characteristics of the devices were measured by heavy ions (HIs) irradiation at 3 different fluences and 15 different nodes of temperature. From these measurements, the effective carrier concentration (ND), reverse current (IR), series resistance (RS), ideal factor (n), and Schottky barrier height (SBH) were calculated and analyzed. Obvious increases of ND and IR were found and some changes of the electronic characteristics with temperature were enhanced by HIs. After the highest fluence of irradiation, the IR at low temperature (20 K) was even larger than the IR at room temperature, which was subjected to lower fluence of irradiation, suggesting risks for aerospace applications. These changes were attributed to defects both at the interface and in the body-substrate induced by irradiation.

Schottky barrier lowering due to interface states in 2D heterophase devices.

The Schottky barrier of a metal–semiconductor junction is one of the key quantities affecting the charge transport in a transistor. The Schottky barrier height depends on several factors, such as work function difference, local atomic configuration in the interface, and impurity doping. We show that also the presence of interface states at 2D metal–semiconductor junctions can give rise to a large renormalization of the effective Schottky barrier determined from the temperature dependence of the current. We investigate the charge transport in n- and p-doped monolayer MoTe2 1T′–1H junctions using ab initio quantum transport calculations. The Schottky barriers are extracted both from the projected density of states and the transmission spectrum, and by simulating the IT-characteristic and applying the thermionic emission model. We find interface states originating from the metallic 1T′ phase rather than the semiconducting 1H phase in contrast to the phenomenon of Fermi level pinning. Furthermore, we find that these interface states mediate large tunneling currents which dominates the charge transport and can lower the effective barrier to a value of only 55 meV.

Indium tin oxid/germanium Schottky photodetectors modulated by ultra-thin dielectric intercalation

Germanium (Ge) photodetectorhas been considered as one of the promising optoelectronic devices for optoelectronic integration. So far, most of reported Ge photodetectors with bulk Ge show high dark currents and low responsivities. In this paper, ultra-thin dielectric interlayer-modulated indium tin oxid (ITO)/Ge Schottky photodetectors with high responsivities and low dark currents are investigated, in which the ultra-thin dielectric interlayers are deposited through atomic layer deposition. The characteristics of ITO/Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; (or MoO&lt;sub&gt;3&lt;/sub&gt;)/Ge Schottky photodiodes fabricated on bulk Ge wafers with various doping concentrations and Ge epilayer on silicon substrates are comparatively studied. It is found that the 2-nm-thick Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; intercalation between ITO transparent electrode and Ge can effectively enhance the Schottky barrier heights of the photodetectors and trap holes at interface states, rendering their dark currents low and responsivities high. The effective Schottky barrier heights increase from 0.34 eV (ITO/i-Ge) to 0.55 eV (ITO/Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;/i-Ge), and from 0.24 eV (ITO/n-Ge) to 0.56 eV (ITO/Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;/n-Ge). While MoO&lt;sub&gt;3&lt;/sub&gt; intercalation between ITO and Ge has no significant effect on the characteristics of all of the photodetectors due to its large electron affinity. The best performance is realized on the ITO/Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;/i-Ge photodetector with a low dark current of 5.91 mA/cm&lt;sup&gt;–2&lt;/sup&gt; at –4 V, sharply dropping by two orders of magnitude, compared with that of the ITO/i-Ge photodetector without the Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; interlayer, and the responsivity is significantly improved to 4.11 A/W at 1310 nm. The ITO/Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;/epi-Ge photodetector fabricated on 500 nm Ge epilayer on a silicon substrate also shows the improved performance with a dark current density of 226.70 mA/cm&lt;sup&gt;2&lt;/sup&gt; at –3 V and a responsivity of 0.38 A/W at 1310 nm, compared with ITO/epi-Ge photodetector. Finally, experiment studies of single-point infrared images at 1310 nm and 1550 nm are carried out with the ITO/Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;/i-Ge photodetector on a two-dimensional &lt;i&gt;XY&lt;/i&gt; displacement platform, which contains 25 pixels and a total detection size of 1750 μm × 1750 μm. The clear and distinguishable images of the infrared spot position are obtained. Consequently, these results suggest that the dielectric interlayer- modulated Schottky photodetectors are competitive in low power consumption and high responsivity, and have great potential applications in the civil field of short wave infrared imaging.

Photosensitivity of Ga2O3 Schottky diodes: Effects of deep acceptor traps present before and after neutron irradiation

The photocurrent produced by 259 nm wavelength excitation was measured in β-Ga2O3 Schottky diodes before and after neutron irradiation. These samples differed by the density of deep acceptors in the lower half of the bandgap as detected by capacitance–voltage profiling under monochromatic illumination. Irradiation led to a very strong increase in photocurrent, which closely correlated with the increase in deep trap density and the decrease after illumination of the effective Schottky barrier height due to hole capture by acceptors. A similar effect was observed on an as-grown βs-Ga2O3 film with a high density of deep acceptors. Electron beam induced current measurements indicated a strong amplification of photocurrent, which is attributed to the Schottky barrier lowering by holes trapped on acceptors near the surface. Photocurrent build-up and decay curves show several time constants ranging from several milliseconds to many seconds. These characteristic times are attributed to tunneling of electrons into the hole-filled acceptors near the surface and to thermal emission of holes from deep acceptors.

The importance of contacts in Cu2GeTe3 phase change memory devices

Cu2GeTe3 (CGT) is a promising phase change material for phase change random access memory (PCRAM) applications because of its high thermal stability in the amorphous phase and its capability to undergo rapid phase change. In this paper, the electrical conduction mechanism of a CGT memory device fabricated using W electrodes (W/CGT) was investigated using current–voltage (I–V) measurements and angle resolved hard x-ray photoelectron spectroscopy (AR-HAXPES). The I–V characteristics of the W/CGT memory device were found to display non-linear behavior in the RESET (amorphous) state, while linear behavior was observed in the SET (crystalline) state, indicating that the W/CGT memory device exhibited Schottky conduction in the RESET state, but Ohmic conduction in the SET state. The effective Schottky barrier height was found to increase linearly as the ideality factor decreased to unity with the ideal W/CGT Schottky barrier height in the RESET state estimated to be 0.33 eV, a value in good agreement with the directly measured Schottky barrier height of 0.35 eV between W and amorphous CGT by AR-HAXPES measurements. These results suggest that the interface between the metal electrode and the phase change material plays an important role in PCRAM devices, and its comprehensive understanding is necessary for future application development.

High-mobility junction field-effect transistor via graphene/MoS2 heterointerface

Monolayer molybdenum disulfide (MoS2) possesses a desirable direct bandgap with moderate carrier mobility, whereas graphene (Gr) exhibits a zero bandgap and excellent carrier mobility. Numerous approaches have been suggested for concomitantly realizing high on/off current ratio and high carrier mobility in field-effect transistors, but little is known to date about the effect of two-dimensional layered materials. Herein, we propose a Gr/MoS2 heterojunction platform, i.e., junction field-effect transistor (JFET), that enhances the carrier mobility by a factor of ~ 10 (~ 100 cm2 V−1 s−1) compared to that of monolayer MoS2, while retaining a high on/off current ratio of ~ 108 at room temperature. The Fermi level of Gr can be tuned by the wide back-gate bias (VBG) to modulate the effective Schottky barrier height (SBH) at the Gr/MoS2 heterointerface from 528 meV (n-MoS2/p-Gr) to 116 meV (n-MoS2/n-Gr), consequently enhancing the carrier mobility. The double humps in the transconductance derivative profile clearly reveal the carrier transport mechanism of Gr/MoS2, where the barrier height is controlled by electrostatic doping.

High-performance high-temperature solar-blind photodetector based on polycrystalline Ga2O3 film

In this paper, high-temperature solar-blind photodetectors were fabricated based on polycrystalline Ga2O3 (poly-Ga2O3) film which was prepared by annealing amorphous Ga2O3 (a-Ga2O3) film in oxygen atmosphere. The effects of annealing temperature on the properties of the material and the performances of the corresponding Metal–semiconductor–metal photodetector were investigated. The main factors affecting device performance are attributed to the oxygen vacancy defect concentration in Ga2O3 and the effective Schottky barrier height and width between gold and Ga2O3. We found that the detector based on 650 °C annealed poly-Ga2O3 showed the best solar-blind detection photoelectric performance and good thermal stability. More interestingly, the device has fast response recovery speed (0.16 s), low dark current (≤0.1 nA) and high photo-to-dark current ratio (≥97) at 200 °C high temperature operation. These performances are even better than the reported high-temperature photodetectors based on high-quality crystal Ga2O3 thin film or Ga2O3 bulk. Besides, our method that avoid direct high-temperature growth of poly-Ga2O3 and may be beneficial to its commercial large-area production and further cost reduction.

Impact of tin-oxide nanoparticles on improving the carrier transport in the Ag/p-GaN interface of InGaN/GaN micro-light-emitting diodes by originating inhomogeneous Schottky barrier height

The effect of tin-oxide (SnO) nanoparticles, which are obtained by indium-tin-oxide (ITO) treatment, on the p-GaN surface of GaN-based flip-chip blue micro-light-emitting diode ( μ -LED) arrays is investigated. A thin Ag layer is deposited on the ITO-treated p-GaN surface by sputtering. SnO nanoparticles originate from inhomogeneous Schottky barrier heights (SBHs) at Ag/p-GaN contact. Therefore, effective SBH is reduced, which causes carrier transport into the μ -LED to enhance. 10 nm thick ITO-treated μ -LEDs show better optoelectronic characteristics among fabricated μ -LEDs owing to improved ohmic contact and highly reflective p-type reflectors. Basically, SnO nanoparticles help to make good ohmic contact, which results in improved carrier transport into μ -LEDs and thus results in increased optoelectronic performances.

Specific Contact Resistivity Improvement by As Preamorphization Implantation for Ti-Based Ohmic Contacts on n+-Si

As preamorphization implant (PAI) for Ti-based ohmic contacts on n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -Si is explored in this article. With As implantation at 3 keV/5 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">13</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> , the specific contact resistivity (ρ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ) of TiSi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> on 1.4 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> P-doped (Nd) n+-Si is significantly reduced by ~33.8%, down to ~2.33 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-8</sup> -cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> . This ρ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> improvement is a result of manipulation between the reduction of effective Schottky barrier height to electrons (φ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">bn,eff</sub> ) and the retardation of Ti silicidation, which are both strongly correlated with As segregation. In comparison with the widely adopted Ge PAI, As PAI shows superior performance for nMOS contact engineering, featuring with lower ρ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> and φ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">bn,eff</sub> as well as better thermal stability.

Effective Schottky barrier lowering of NiGe/p-Ge(100) using Terbium interlayer structure for high performance p-type MOSFETs

Ultra-low contact resistance at the interface between NiGe and p-Ge, i.e., NiGe/p-Ge was achieved by introducing terbium (Tb) as an interlayer in forming NiGe using Tb/Ni/TiN structure. The contact resistance value obtained using the circular transmission line model for an 8-nm thick Tb interlayer sample was 7.21 × 10−8 Ω·cm2, which is two orders of magnitude less than that of reference sample (without the Tb interlayer) of 7.36 × 10−6 Ω·cm2. The current–voltage characteristics were studied at a temperature range of −110 ~ 25 °C to determine the effective Schottky barrier height (eSBH). An eSBH of 0.016 eV was obtained for the 8-nm thick Tb interlayer. Various Tb interlayer thicknesses were selected to study their effect on the contact resistance. The Tb interlayer surface and structural properties were characterized using FESEM, XRD, XPS, TEM, and SIMS analyses.

Effective Schottky Barrier Height Model for N‐Polar and Ga‐Polar GaN by Polarization‐Induced Surface Charges with Finite Thickness

The nitrogen‐polar GaN material system is a promising candidate for high‐frequency applications, such as those in the millimeter‐wave range. Schottky barrier height is one of fundamental parameters necessary for device applications of N‐polar GaN. Herein, vertical Schottky diodes for both N‐polar and Ga‐polar GaN are prepared, and it is found through experiments that the barrier height of N‐polar GaN is smaller than that of Ga‐polar GaN by 0.21 V. This difference in the barrier height stems from the polarization‐induced surface charge layer of a few angstroms thickness under the surface. Numerical calculation of band profiles suggests that a significant band bending caused by the large amount of polarization charges pushes the conduction band energy downward (upward) in the N‐polar (Ga‐polar) surface depending on the sign of the polarization charges, which results in two different effective Schottky barrier heights. This difference is explained by assuming the polarization‐charge layer thickness of about 5 Å. A simple analytical model to estimate the difference in barrier heights between the two polarities is also proposed.

Effects of Ni Film Thickness on the Properties of Ni-Based Silicides Formed on Both Highly Doped n- and p-Si Substrate

Ni-based silicides continue to play an indispensable role during the remarkable development of microelectronics. In this work, on both highly boron (B)-doped n-Si and phosphorus (P)-doped p-Si substrate, the effects of the thickness of initial Ni films on Ni-based silicides properties are investigated comprehensively. Ni films with varying thicknesses from 1–10 nm are deposited followed by rapid thermal annealing (RTP) to form Ni-based silicides. Sheet resistance, phase identity, thermal stability and dopant redistribution are versatilely characterized by four-point probe, X-ray diffraction (XRD), Raman spectroscopy, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Secondary Ion Mass Spectroscopy (SIMS). It is found that the dopants tend to segregate at silicides/Si interface when the thickness of Ni films is 3 nm or less, which is paramount beneficial to reduce effective Schottky barrier heights (SBHs) thus lowering specific contact resistivity (ρc).

Effects of ultraviolet illumination on 4H-SiC Schottky barrier diodes irradiated by swift heavy ions

In this study, the capacitance-voltage (C-V) and current-voltage (I-V) characteristics of 4H-SiC Schottky barrier diode (SBD) irradiated by swift heavy ions (SHI) are studied under different ultraviolet (UV) conditions. The effective carrier concentration (ND), reverse current (IR), series resistance (RS), ideal factor (n) and Schottky barrier height (SBH) are calculated and analyzed. Furthermore, by analyzing the parameters, especially, ND, IR and n, a physical model is built. The UV illumination dependence of the recombination center states for defects or defect-states is presented.

Physical origins of the ideality factor of the current equation in Schottky junctions

After the carrier drift velocity at the semiconductor / metal interface is considered, current transport in Schottky diodes under a forward electric field is physically modelled. This model reveals that the ideality factor can be physically originated from the drift velocity and the drift velocity can also reduce the effective Schottky barrier height. This proposed model predicts that both the ideality factor and the Schottky barrier height depend on temperature, voltage and doping density, which agree well with the experimental results reported in the literature. The proposed diode current model also predicts a linear dependent relation between the reciprocal of the ideality factor and the effective Schottky barrier height, which is validated by experimental results. Such a model is useful to better understand the thermionic emission current physically in semiconductor / metal contact. It is also useful to characterise the material properties by using the ideality factor.

The influence of ion-implantation on the effective Schottky barrier height of NiGe/n-Ge contacts

The mechanism for modulating the effective Schottky barrier height of NiGe/Ge contacts by incorporating impurities is still under debate. There is a view that impurities segregated at the NiGe/Ge interface act as donors or passivators that alleviate the Fermi-level pinning effect so as to significantly affect the electrical characteristics. Our study, however, clearly demonstrates that ion implantation damage is the primary factor in causing the lowering of the effective Schottky barrier, for NiGe/n-Ge contacts doped with Se or Si, although passivation behavior is observed for P doping.

On MoS2 Thin-Film Transistor Design Consideration for a NO2 Gas Sensor.

MoS2 thin-film transistors (TFTs) are fabricated and simulated to explore the NO2 gas sensing mechanism depending on different device structures. In particular, the role of the Al2O3 passivation layer on the MoS2 channel has been investigated. In the case of nonpassivated MoS2 TFTs, increase of off-current is observed with NO2 gas, which has been modeled with the modulation of the effective Schottky barrier height for holes because of the generation of in-gap states near the valence band as NO2 gases interact with the MoS2 channel. The nonpassivated MoS2 TFTs are simulated based on nonequilibrium Green's function method, and the simulation results do confirm this sensing mechanism. On the other hand, MoS2 TFTs with the Al2O3 passivation layer have been modeled with a pseudo-double gate structure as NO2 gases on the capping layer can act like the secondary gate inducing the positive charge state. Our quantum transport simulation shows that the significant threshold voltage shift can be achieved with NO2 gas, which matches the experimental observation, thereby exhibiting a completely different sensing mechanism of the passivated device from the nonpassivated counterpart. In addition, we also discuss competing device parameters for the passivated MoS2 TFTs by varying the main and the secondary gate dielectric, suggesting co-optimization to realize high sensitivity and low power consumption simultaneously.

Control of the Boundary between the Gradual and Abrupt Modulation of Resistance in the Schottky Barrier Tunneling-Modulated Amorphous Indium-Gallium-Zinc-Oxide Memristors for Neuromorphic Computing

The transport and synaptic characteristics of the two-terminal Au/Ti/ amorphous Indium-Gallium-Zinc-Oxide (a-IGZO)/thin SiO2/p+-Si memristors based on the modulation of the Schottky barrier (SB) between the resistive switching (RS) oxide layer and the metal electrodes are investigated by modulating the oxygen content in the a-IGZO film with the emphasis on the mechanism that determines the boundary of the abrupt/gradual RS. It is found that a bimodal distribution of the effective SB height (ΦB) results from further reducing the top electrode voltage (VTE)-dependent Fermi-level (EF) followed by the generation of ionized oxygen vacancies (VO2+s). Based on the proposed model, the influences of the readout voltage, the oxygen content, the number of consecutive VTE sweeps on ΦB, and the memristor current are explained. In particular, the process of VO2+ generation followed by the ΦB lowering is gradual because increasing the VTE-dependent EF lowering followed by the VO2+ generation is self-limited by increasing the electron concentration-dependent EF heightening. Furthermore, we propose three operation regimes: the readout, the potentiation in gradual RS, and the abrupt RS. Our results prove that the Au/Ti/a-IGZO/SiO2/p+-Si memristors are promising for the monolithic integration of neuromorphic computing systems because the boundary between the gradual and abrupt RS can be controlled by modulating the SiO2 thickness and IGZO work function.