Metal Insulator Semiconductor Research Articles

Engineering the SiOx interfacial layer of Si-based metal-insulator-semiconductor junction for photoelectrochemical hydrogen production

Photoelectrochemical (PEC) water splitting provides a potential method to produce renewable hydrogen energy, but there is still plenty of room for improving the efficiency and stability of photoelectrodes. In this paper, we present a metal–insulator-semiconductor (MIS) structure based on p-Si that enables stable and efficient water splitting by engineering the interfacial insulating layer. The silicon oxide (SiOx) film with appropriate thickness and low defects is regrown by a chemical oxidation process, which provides a high-quality insulating layer to passivate the p-Si. The carrier flux, barrier height and interfacial resistance of p-Si based MIS junction can be systematically tuned by controlling the thickness and quality of SiOx layer. Under AM 1.5G illumination, the optimized p-Si/SiOx/Ti/Pt photoelectrode shows an onset potential of 0.5 V vs. RHE, a maximum photocurrent of 28 mA/cm2 and a high applied bias photon-to-current efficiency (ABPE) of 6 %. These results have significant implications for constructing MIS photoelectrodes towards effective water splitting.

Design of an ultrafast plasmonic nanolaser for high-intensity broadband emission operating at room temperature

We propose a plasmonic nanolaser based on a metal–insulator–semiconductor–insulator–metal (MISIM) structure, which effectively confines light on a subwavelength scale (∼λ/14). As the pump power increases, the proposed plasmonic nanolaser exhibits broadband output characteristics of 20 nm, and the maximum output power can reach 20 µW. Furthermore, the carrier lifetime at the upper energy level in our proposed structure is measured to be about 400 fs using a double pump-probe excitation. The ultrafast characteristic is attributed to the inherent Purcell effect of plasmonic systems. Our work paves the way toward deep-subwavelength mode confinement and ultrafast femtosecond plasmonic lasers in spaser-based interconnected, eigenmode engineering of plasmonic nanolasers, nano-LEDs, and spontaneous emission control.

Unveiling Sub-60 mV/decade Subthreshold Swing in The Oxide Local Thinning (OLT) Gated MIS Tunnel Diodes by TCAD Simulations

In this study, we unveil the sub-60 mV/decade subthreshold swing (SS) characteristics observed in the oxide local thinning (OLT) gated p-type metal-insulator-semiconductor (MIS) tunnel diodes (TD) utilizing TCAD simulations. Through our simulations, we successfully replicate the sub-60 mV/decade SS behavior and attribute this remarkable characteristic to the rapid increase in electron density near the gate edge. This phenomenon arises from electron injection through the gate OLT region under a negative gate voltage, leading to a significant elevation in electron density near the gate edge. Armed with this insight, we design scaled devices to assess the feasibility of achieving sub-60 mV/decade SS behavior. By modulating the substrate thickness, we effectively simulate devices with SS lower than 60 mV/decade across a current range spanning 8 orders of magnitude.

Electrical Properties of Laser Patterned Schottky Diode with ALD-Grown TiO2 Interlayer.

Heterojunction formation is the key to adjusting the electronic and optoelectronic properties of various semiconductor devices. There have been various reports on the formation and importance of semiconducting heterojunction devices based on metal oxides. Titanium dioxide (TiO2) is one of the metal oxides that has many unique properties. TiO2's importance is due to its physical and chemical properties such as large band gap, large permittivity, stability, and low leakage current density. In this context, we present the electrical properties of the metal-insulator-semiconductor (MIS) type-TiO2-based Schottky barrier diode (SBD) in the study. To create a thin layer of TiO2 on p-type silicon (p-type Si) patterned partially by the laser-induced periodic surface structure (LIPSS) technique, an atomic layer deposition (ALD) technique was used in the study. For comparison, the current-voltage (I-V) characteristics of the TiO2-based laser-patterned (LP) and nonlaser-patterned (non-LP) diodes were measured at 300 K and in the dark at ±5 V. Classical thermionic emission (TE) theory and Cheung functions were used to investigate the critical diode parameters of the diodes, including ideality factor (n), series resistance (Rs), and barrier height (Φb). The n values were obtained as 4.10 and 3.68 from the TE method and Cheung functions for the LP diode, respectively. The Φb values were found as 0.68 and 0.69 eV from the TE method and Cheung functions, respectively. According to experimental results, the laser patterning resulted in an increase in the Φb values and a decrease in the n values. After laser patterning, it was observed that the device worked effectively, and the ideality factor and barrier height values were improved. This study provides insight into the fabrication and electrical properties of TiO2-based heterojunction devices.

Investigation into the impact of bulk defects in the drift layer on the electrical properties of GaN-based trench Schottky barrier diodes

Using numerical simulation tools, this work systematically investigates the impact of bulk defects in the drift layer on GaN-based trench metal–insulator–semiconductor barrier-controlled Schottky rectifiers. Investigations show that in forward conduction, the acceptor-type defects significantly increase the on-resistance (R on.sp). When the device is in reverse blocking mode, donor-type defects tend to weaken the charge-coupling effect, leading to early breakdown of the device, while acceptor-type defects show the opposite feature. In addition, our report identifies that the reverse blocking effect is significantly impacted when the defects are located in the region with maximum electric field magnitude. We also find that the acceptor-type traps generate a remarkable charging/discharging effect, which will destabilize the dynamic forward conduction process. Hence, we numerically prove that bulk defects should be avoided in actual power diodes.

Control of Surface Chemistry in Recess Etching toward Normally Off GaN Metal–Insulator–Semiconductor High‐Electron‐Mobility Transistors

Reducing off‐state and gate leakage current is crucial in the development of metal–insulator–semiconductor high‐electron‐mobility transistors (MIS‐HEMTs). This work reports interface engineering in the gate recess region through low‐damage digital etching during the fabrication of normally off GaN MIS‐HEMTs. Conventional plasma etching leads to a reduction of the N/(Al+Ga) ratio, but this value recovers to almost 1 with optimized oxidation condition during digital etching, suggesting a reduction of the Al/Ga dangling bonds based on the proposed technique. GaN MIS‐HEMTs with digital etching exhibits a threshold voltage of 1.0 V at 1 μA mm−1, a high ON/OFF current ratio of 1010, a gate breakdown voltage of 22 V, and a low gate leakage current of 10−8 mA mm−1.

Influence of Baccharis salicifolia Extract on Iron Oxide Nanoparticles in MCM-41@IONP and Its Application in Room-Temperature-Fabricated Metal–Insulator–Semiconductor Diodes

This work presents the green synthesis of iron oxide nanoparticles (IONPs) using Baccharis salicifolia extract and their incorporation in mesoporous silica MCM-41, obtaining an MCM-41@IONP composite. The MCM-41@IONP composite was characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), nitrogen adsorption and desorption, scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The use of the natural reducing agent Baccharis salicifolia resulted in nanoparticles with an average size of 31 nm. Furthermore, we showcase the application of the MCM-41@IONP nanocomposite in a metal–insulator–semiconductor (MIS) diode, which was fabricated at room temperature. The current–voltage and capacitance–voltage curves of the MIS diode were carefully measured and subjected to detailed analysis. The results demonstrate the potential utility of MCM-41@IONP nanocomposite-based MIS diodes, suggesting their applicability in the design of biosensors or as discrete components in electronic devices.

Comparative Study on Schottky Contact Behaviors between Ga- and N-Polar GaN with SiNx Interlayer

We conducted a comparative study on the characterization of Ga-polar and N-polar GaN metal–insulator–semiconductor (MIS) Schottky contact with a SiNx gate dielectric. The correlation between the surface morphology and the current–voltage (I–V) characteristics of the Ga- and N-polar GaN Schottky contact with and without SiNx was established. The insertion of SiNx helps in reducing the reverse leakage current for both structures, even though the leakage is still higher for N-polar GaN, consistent with the Schottky barrier height calculated using X-ray photoelectron spectroscopy. To optimize the electric property of the N-polar device, various substrate misorientation angles were adopted. Among the different misorientation angles of the sapphire substrate, the GaN MIS Schottky barrier diode grown on 1° sapphire shows the lowest reverse leakage current, the smoothest surface morphology, and the best crystalline quality compared to N-polar GaN grown on 0.2° and 2° sapphire substrates. Furthermore, the mechanism of the reverse leakage current of the MIS-type N-polar GaN Schottky contact was investigated by temperature-dependent I–V characterization. FP emissions are thought to be the dominant reverse conduction mechanism for the N-polar GaN MIS diode. This work provides a promising approach towards the optimization of N-polar electronic devices with low levels of leakage and a favorable ideality factor.

Electrical and dielectric behaviors of Al/SiO2-surfactant/n-Si schottky structure in wide range of voltage and frequency

SiO2 surfactant insulator into Al/n-Si metal-semiconductor (MS) structure was fabricated into Al/SiO2-surfactant/n-Si metal–insulator–semiconductor (MIS) structure and its effect on the electrical properties of the final structure was investigated. The SiO2-surfactant layer is coated on the n-Si wafer by the spin coating technique. The I-V data is used to calculate the fundamental electrical parameters of this MIS structure. The density distribution of the surface states (Nss) is computed depending on the energy at forward potential. The current conduction mechanisms (CCMs) in the MIS structure are examined at the reverse and forward biases applied. To get more accurate and reliable results, the profiles of I-V and C/(G/ω)-V are measured at a wide range of bias voltage (0.25V-4V) and frequency (1kHz-1MHz), respectively. The performance of the MIS is significant due to the basic values of electrical parameters (n, I0, Rs, Rsh, Nss, ΦB0, and Rectifying Ration (RR)) and dielectric parameters (ε′, ε″, tan δ, M′, M″, Rs, and σ) compared with the MS structure. The other electrical parameters (ND, WD, Em, ΦΒ) are extracted from the slope and intercept of the reverse bias C−2-V plot as a function of frequency. Furthermore, the profile of voltage-dependent Rs and Nss was determined using different methods from I-V and C/G-V data and examined comparatively with each other. The changes in impedance properties with frequency and voltage of the MIS are discussed in detail.

Sol-Gel Multilayered Niobium (Vanadium)-Doped TiO2 for CO Sensing and Photocatalytic Degradation of Methylene Blue.

Multilayered TiO2 films doped either with Niobium or Vanadium (1.2 at. %) were deposited by the sol-gel dip coating method on c-Si and glass substrates. The films on glass substrates were tested for CO sensing and photocatalytic degradation of methylene blue. X-ray diffraction data analysis showed that all the TiO2:Nb(V) films were nanocrystalline in the anatase phase, with a uniform and compact microstructure and a homogeneous superficial structure of small grains with diameters in the range of 13-19 nm. For the electrical characterization, the TiO2:Nb(V) films were incorporated in Metal-Insulator-Semiconductor (MIS) structures. The specific resistivity is of the order of 104 Ωcm and its value decreases with increasing the electrical field, which testifies to the injection of electrons into these layers. From the analysis of the current-voltage curves taken at different temperature- and frequency-dependent capacitance-voltage and conductance-voltage characteristics, the density and parameters of deep levels in these TiO2 films are evaluated and the electron charge transport mechanism is established. It was shown that the current in these TiO2:Nb(V)-Si MIS structures is mainly carried out by inter-trap tunneling via deep levels energetically distributed in the TiO2 bandgap. Testing these sol-gel TiO2:Nb(V) layers for gas sensing and photocatalytic capabilities proved that they could serve such purposes. In particular, the results of the V-doped sol-gel TiO2 film confirm its CO detection capability, which is rarely reported in the literature. For the photodegradation of methylene blue, the Nb-doped TiO2 samples were superior, with nearly double the photocatalytic efficiency of undoped TiO2.

Analysis on the capacitance-voltage characteristics of metal-insulator-semiconductor capacitors based on thermally evaporated WOx on n- and p- type crystalline silicon

Tungsten oxide (WOx) thin films were deposited on n- and p-type crystalline silicon (c-Si) wafers by thermal evaporation technique at room temperature. The electrical characterization of Ag/WOx/n-Si and Ag/WOx/p-Si metal–insulator-semiconductor (MIS) capacitors were examined by the capacitance- and conductance-voltage measurements as a function of applied frequency in the 10 kHz 10 MHz range. The admittance properties of both MIS devices have been evaluated by analyzing the interfacial nature and bulk c-Si in accumulation, depletion, and inversion regimes. The capacitance responses of interface traps, bulk c-Si, depletion, and shallow states at the WOx/c-Si interface indicated the appearance of the capacitance peaks in depletion and inversion regimes for Ag/WOx/n-Si and Ag/WOx/p-Si devices. From C-V characterization, various parameters such as the depletion layer width, depletion capacitance, flat-band voltage, total charge density, and net ionized state density were calculated as a function of applied frequency. For Ag/WOx/n-Si device, the total charge density and barrier height values of 7.642 × 10−9 C and 1.119 eV at 1 MHz, respectively, were obtained. The same parameters were calculated to be 5.887 × 10−8 C and 1.107 eV for Ag/WOx/p-Si. The results demonstrated that interfacial nature of WOx film significantly governs the electronic characteristics of the c-Si based MIS devices.

Transport and dielectric properties of MIS structure with embedded Si QDs (AuPd/SiO2:Si QDs/n-Si) grown by MBE

This study focuses on the growth of silicon quantum dots (Si QDs) on insulator substrates via solid-state dewetting of ultrathin silicon films deposited by molecular beam epitaxy (MBE). The resulting Si QDs exhibit well-defined spherical shapes, low size dispersion with an average diameter of 6 nm, and a high density (1012/cm2), making them ideal for microelectronic applications. Current-voltage spectroscopy and impedance spectroscopy were employed to investigate the electrical transport and dielectric properties of Si QDs integrated into a metal-insulator-semiconductor (MIS) structure (AuPd/SiO2: Si QDs/n-Si). Current-voltage measurements reveal that the insertion of Si QDs into the MIS structure improves the electrical transport by introducing new conduction mechanisms. Impedance measurements demonstrate the influence of Si QDs on the frequency dependence of the real part of the dielectric constant (ε′) and the loss tangent (tan δ). Furthermore, Si QDs impact both the real (M′) and imaginary (M″) parts of the electric modulus. Despite slight deviations in dielectric properties, the MIS structure retains its fundamental nature. These investigations affirm the high electrical quality of Si QDs grown via solid-state dewetting and offer valuable insights for researchers engaged in the development of Si QD-based devices, such as non-volatile memories and MIS photodetectors.

J-MISFET Hybrid Dual-Gate Switching Device for Multifunctional Optoelectronic Logic Gate Applications.

High-performance and low operating voltage are becoming increasingly significant device parameters to meet the needs of future integrated circuit (IC) processors and ensure their energy-efficient use in upcoming mobile devices. In this study, we suggest a hybrid dual-gate switching device consisting of the vertically stacked junction and metal-insulator-semiconductor (MIS) gate structure, named J-MISFET. It shows excellent device performances of low operating voltage (<0.5 V), drain current ON/OFF ratio (∼4.7 × 105), negligible hysteresis window (<0.5 mV), and near-ideal subthreshold slope (SS) (60 mV/dec), making it suitable for low-power switching operation. Furthermore, we investigated the switchable NAND/NOR logic gate operations and the photoresponse characteristics of the J-MISFET under the small supply voltage (0.5 V). To advance the applications further, we successfully demonstrated an integrated optoelectronic security logic system comprising 2-electric inputs (for encrypted data) and 1-photonic input signal (for password key) as a hardware security device for data protection. Thus, we believe that our J-MISFET, with its heterogeneous hybrid gate structures, will illuminate the path toward future device configurations for next-generation low-power electronics and multifunctional security logic systems in a data-driven society.

Electrical and dielectric characterization of Ge quantum dots embedded in MIS structure (AuPd/SiO2:Ge QDs/n-Si) grown by MBE

Monocrystalline Germanium quantum dots (Ge QDs), grown by molecular beam epitaxy (MBE), are intricately embedded within a SiO2 oxide layer of a metal-insulator-semiconductor (MIS) structure, catering to optoelectronic applications. These monocrystalline Ge QDs exhibit high density (D ∼ 5 x 1012 cm−2), possess a spherical morphology, and an average size of 6 nm with narrow size distribution. A comprehensive investigation into the influence of these quantum dots on the electrical transport and dielectric properties of the metal-insulator-semiconductor (MIS) structure was conducted through current-voltage (I–V) spectroscopy and impedance spectroscopy. Notably, I–V measurements demonstrate that Ge QDs enhance conduction phenomena, thereby improving electrical transport within the MIS structure. Furthermore, the capacitance-voltage (C–V) and conductance-voltage (G-V) measurements, spanning the inversion and accumulation regions, demonstrate a memory effect induced by Ge QDs within the MOS structure. Extensive analysis of dielectric parameters, including permittivity (ε′), dielectric loss (ε”), dissipation factor (tanδ), as well as electrical modulus (M’ and M”), across a broad frequency range and under varying bias voltages, reveals no anomalous electrical or dielectric behavior attributable to the presence of Ge QDs in MIS structure. Consequently, these findings affirm the viability of the novel MIS structures with Ge QDs for the development of optoelectronic devices such as photodetectors or solar cells.

Wafer-Scale Si-Based Metal–Insulator–Semiconductor Photoanodes for Water Oxidation Fabricated Using Thin Film Reactions and Multiple-layer Electrodeposited Catalysts

Wafer-Scale Si-Based Metal–Insulator–Semiconductor Photoanodes for Water Oxidation Fabricated Using Thin Film Reactions and Multiple-layer Electrodeposited Catalysts

Electrical and dielectric properties of ferromagnetic GeMn nanocrystals embedded in metal-oxide-semiconductor Schottky diodes (Al/SiO2:GeMn NCs/n-Si) grown by MBE

This study examines the electrical and dielectric characteristics of magnetic GeMn nanocrystals integrated into a metal-insulator-semiconductor (MOS) configuration for optoelectronic applications. The nanocrystals were produced by solid-state dewetting of an amorphous GeMn layer deposited by MBE on SiO2/Si. The nanocrystals exhibit a well-defined hemispheric shape, high homogeneity, and with a Curie temperature higher than that of the ambient temperature. Characterizations by transmission electron microscopy (TEM) coupled with energy-dispersive X-ray spectroscopy (EDS) revealed the crystallinity of the nanocrystals and optimal incorporation of manganese in the nanocrystals, eliminating the usual diffusion or segregation anomalies observed during growth of GeMn alloy on silicon or germanium. Electrical and dielectric tests conducted via current-voltage and impedance spectroscopies on these structures confirmed the integrity of the oxide layer surrounding the GeMn nanocrystals from defects associated with the manganese. In addition, these measurements validated the proper functioning of the MOS structure as a MOS-type Schottky diode. The in-depth analysis of dielectric parameters, such as permittivity (ε), tangent δ, and electric modulus (M) as a function of frequency and bias voltage, revealed no anomalies, thus reinforcing the high quality of the MOS structure enclosing the GeMn nanocrystals.These results mark a significant advance in the growth and integration of magnetic semiconductor nanostructures for optoelectronic applications, paving the way for promising technological developments.

Non-equilibrium thermal transport study in steady state GaN MISHEMT channel layer based on electron Monte Carlo and phonon BTE

An electro-thermal coupling simulator for GaN devices based on electron Monte Carlo (e-MC) simulations is established. Taking GaN Metal Insulator Semiconductor High Electron Mobility Transistor (MISHEMT) as example, the non-equilibrium thermal transport processes of self-heating effect in the channel layer are studied. This simulator is mainly coupled by e-MC and the phonon Boltzmann transport equation (pBTE), physical property parameters and electric field parameters are provided by first-principles and Technology Computer Aided Design (TCAD), respectively. We first verify the e-MC program by calculating the electron transport properties of GaN materials, verify the feasibility of the established GaN MISHEMT model by using TCAD and obtained its operating characteristics. Further, the simulator is used to evaluate the non-equilibrium processes inside the channel layer in detail, the results show that there is significant consistency in the peak positions of electric field strength, heat generation and diffusion temperature, the diffusion temperature peak occurs at the secondary peak of heat generation. The frequency distribution of phonon emission under different drain-source bias voltages is revealed by phonon emission spectrum analysis. The strength of the non-equilibrium effect is measured by effective temperature. Increasing the drain-source bias voltage will significantly increase the peak temperature of hotspot and further enhance the non-equilibrium effect. Our study reports an efficient scheme for electro-thermal simulations of GaN MISHEMT, which provides insights for thermal management of GaN-based transistor devices.

Effect of Ultra‐Thin AlGaN Regrown Layer on the Electrical Properties of ZrO2/AlGaN/GaN Structures

Effects of the ultrathin 1 nm thick AlGaN regrown layer before gate insulator deposition on the performance of ZrO2/AlGaN/GaN metal‐insulator‐semiconductor (MIS) structures are investigated. In comparison with the reference ZrO2/AlGaN/GaN MIS high‐electron‐mobility transistors (MIS‐HEMTs), MIS‐HEMTs with AlGaN regrown layer exhibit increased maximum drain current (&gt;1050 mA mm−1) and broader full‐width at half maximum (FWHM) of transconductance profile (11 V). Moreover, the gate leakage current in the forward direction is reduced by about four orders of magnitude while the hysteresis of the transfer curves is cut‐down to more than 40%. Compared with the control MIS‐capacitors (MIS‐caps), MIS‐caps with regrowth show highly evident sudden increase in capacitance known as “spill‐over” in the capacitance–voltage (C–V) profiles, suggesting improved ZrO2/AlGaN interfaces. Extracted electron states from the C–V profiles, reveal 6 times to 14 times reduction of interface states density within 0.2 to 0.8 eV from the AlGaN conduction band edge. Using photo‐assisted C–V measurements, the near mid‐gap electron states density of MIS‐caps is extracted with regrowth to be at least three times less than those of reference MIS‐caps. Findings in this work are very similar to those recently reported Al2O3/regrown‐AlGaN interfaces, suggesting that the regrowth technique could be universal in reducing electron states along insulator/AlGaN interfaces.

Comparative study of the interface passivation properties of LiF and Al2O3 using silicon MIS capacitor

Lithium fluoride (LiF) is currently a very popular dielectric material used as a passivation or transport layer in a variety of applications, especially in high-efficiency solar cells. Despite this, its conduction properties and interface behavior with silicon remain largely unexplored. In this work, a LiF metal–insulator–semiconductor (MIS) structure is fabricated and characterized, and its properties are compared to the well-understood aluminum oxide (Al2O3) MIS structure. First, a higher current density in LiF compared to Al2O3 is highlighted, as well as its PN junction-like behavior with n-type silicon (n-Si), being rather unconventional for a dielectric layer. C–V measurements showcase the likely presence of an interface defect, causing an increase in the apparent doping and a shift in the flatband voltage VFB by +70 meV. This defect is found to be of the acceptor type, which renders the interface fixed charge more negative and improves the field-effect passivation in the case of a negative Qf. Finally, a density of interface states Dit≈2×1011 cm−2 eV−1 was found for LiF/n-Si, which is a low value showing appropriate chemical passivation at the interface. Overall, this work enables us to shed more light on the interface properties of LiF on n-Si, which is an essential step toward its wider use in state-of-the-art solar cells and other silicon-based devices.

Efficiency improvement by using metal–insulator-semiconductor structure in InGaN/GaN micro-light-emitting diodes

InGaN/GaN micro-light-emitting diodes (micro-LEDs) with a metal–insulator-semiconductor (MIS) structure on the sidewall are proposed to improve efficiency. In this MIS structure, a sidewall electrode is deposited on the insulating layer-coated sidewall of the device mesa between a cathode on the bottom and an anode on the top. Electroluminescence (EL) measurements of fabricated devices with a mesa diameter of 10 μm show that the application of negative biases on the sidewall electrode can increase the device external quantum efficiency (EQE). In contrast, the application of positive biases can decrease the EQE. The band structure analysis reveals that the EQE is impacted because the application of sidewall electric fields manipulates the local surface electron density along the mesa sidewall and thus controls surface Shockley–Read–Hall (SRH) recombination. Two suggested strategies, reducing insulator layer thickness and exploring alternative materials, can be implemented to further improve the EQE of MIS micro-LEDs in future fabrication.Graphical