Fabrication Of Schottky Diodes Research Articles

Non-covalent functionalized Schottky interface at Ti3C2Tx/c-Si van der Waals heterojunction

Synergistic interaction between 2D materials and organic molecules presents an additional dimension for tuning their intrinsic properties. Herein, we aim totune the work function of 2D Ti3C2Txby introducing ultrathin interlayers of organic dipoles (O.D.) with a defined dipole moment value. Interface engineering is achieved through the inclusion of poly(ethylene)amine (PEI 0.1 %) and third generation poly(amido-)amine (PAMAM G3), between the Ti3C2TXand c-Si. c-Si/O.D./Ti3C2Tx heterostructures were fabricated by simple drop casting of the aqueous MXene solution on O.D. coated c-Si substrates. Charge transport properties of the fabricated Schottky diodes with structure of c-Si/O.D./Ti3C2TXwere evaluated through systematic analysis of the I-V and C-V characteristics. Our investigations reveal that diodes featuring O.D. as interlayers exhibit substantially reduced reverse saturation current density (J0) and enhanced built-in potential (Vbi).Work function of the fabricated c-Si/MXene/O.D. structures were evaluated from the ultraviolet photo-emission spectroscopy (UPS) measurements. We report a significant reduction in the work function value of Ti3C2Txfrom 5.8 eV to 4.2 eV for Ti3C2Tx/PEI 0.1 % and 3.3 eV for Ti3C2Tx/PAMAM-G3 heterostructures. Our studyintroduces an innovative approach for modifying the work function of Ti3C2Tx through the incorporation of O.D., highlighting the versatility of MXene electrodes to shape the future optoelectronic devices.

Isolation of a Cd-Based Coordination Polymer Containing Mixed Ligands: Time- and Temperature-Dependent Synthesis, Sulfonamide Antibiotics Detection, and Schottky Diode Fabrication.

In this study, we present a new cadmium(II)-based two-dimensional coordination polymer [Cd (L)(NA)(H2O)] (L = Iminol form of N-nicotinoyl glycinate, NA = nicotinate), 1, containing two linkers generated from N-nicotinoyl glycine. A comprehensive investigation was carried out during the synthesis of the coordination polymers by varying the reaction time interval and temperature, and it revealed the formation of three distinct phases, of which two phases were previously reported and one was a new compound (1). The structure of compound 1 was determined by single-crystal X-ray diffraction, and it shows a corrugated layer structure with hydrogen bond interactions leading to three-dimensional supramolecular arrangements. Compound 1 exhibited strong emission at 420 nm when excited at 260 nm in an aqueous medium. The emission behavior of this compound was used for the detection of various sulfonamide antibiotics, sulfadiazine, sulfamethazine, sulfachloropyridazine, sulfameter, sulfaquinoxaline, and sulfathiazole, in the presence of common water pollutants. The luminescence quenching response of compound 1 to sulfonamide antibiotics was significant, ranging from 81 to 94%, and the detection sensitivity reached parts per billion (ppb) levels (226-726 ppb). Compound 1 also used for the fabrication of Schottky diode devices with a barrier height of 0.86 eV along with an excellent ideality factor of 1.24.

Characterization of Bi-doped ZnO nanorods prepared by chemical bath deposition method

This study investigates the effect of bismuth (Bi) doping on the structural, optical and electrical properties of ZnO nanorods prepared using a chemical bath deposition process. X-ray diffraction shows that the prepared nanorods are crystalline, and that Bi is successfully incorporated into the ZnO lattice. Scanning electron microscopy reveals an enhancement in the growth-rate upon Bi doping while X-ray photoelectron spectroscopy confirms the presence of Bi2O3 for Bi concentrations ≥ 2 at.%. Room temperature UV and deep-level emission peaks are observed in the as-grown ZnO nanorods. Following annealing at 573 K, in oxygen, only sharp UV luminescence peaks remain. Additinally, a blueshift in the optical band gap is observed following Bi doping. The current–voltage characteristics of the fabricated Schottky diodes show improved rectification behaviour after Bi doping. The best device is obtained at 3 at.% Bi with a Schottky barrier height and an ideality factor of 0.70 eV and 1.86, respectively.

Characterization of (001) β-Ga2O3 Schottky diodes with drift layer grown by MOCVD

Growing a thick high-quality epitaxial layer on the β-Ga2O3 substrate is crucial in commercializing β-Ga2O3 devices. Metal organic chemical vapor deposition (MOCVD) is also well-established for the large-scale commercial growth of β-Ga2O3 and related heterostructures. This paper presents a systematic study of the Schottky barrier diodes fabricated on two different Si-doped homoepitaxial β-Ga2O3 thin films grown on Sn-doped (001) and (010) β-Ga2O3 substrates by MOCVD. X-ray diffraction analysis of the MOCVD-grown sample, room temperature current density–voltage data for different Schottky diodes, and C–V measurements are presented. Diode characteristics, such as ideality factor, barrier height, specific on-resistance, and breakdown voltage, are studied. Temperature dependence (170–360 K) of the ideality factor, barrier height, and Poole–Frenkel reverse leakage mechanism are also analyzed from the J–V–T characteristics of the fabricated Schottky diodes.

Suppression of the Carbon Vacancy Traps and the Corresponding Leakage Current Reduction in 4H-SiC Diodes by Low-Temperature Implant Activation in Combination With Oxidation

Junction barrier Schottky diode fabrication involves multi-folded Al ion implantation for realizing p-type doping. With a new fabrication recipe, we demonstrate that the trade-off between sufficiently high Al acceptor activation and sufficiently low residual concentration of carbon vacancies - acting as free carrier traps - may be resolved applying relatively low temperature anneals (1700°C), followed by the thermal oxidation which leads to in-diffusion of the carbon interstitials from the C-rich sacrifice-oxide/SiC interface. Specifically, we detected two major interconnected factors: suppression of the carbon vacancies and dramatic reduction of the reverse leakage current (by 32 times at -1200 V). The reduction of the reverse biased current is correlated with the removal of the carbon vacancies, interconnected with the Poole-Frenkel emission contribution to the leakage current.

Highly Sensitive MoS2 Photodetectors Enabled with a Dry-Transferred Transparent Carbon Nanotube Electrode.

Fabricating electronic and optoelectronic devices by transferring pre-deposited metal electrodes has attracted considerable attention, owing to the improved device performance. However, the pre-deposited metal electrode typically involves complex fabrication procedures. Here, we introduce our facile electrode fabrication process which is free of lithography, lift-off, and reactive ion etching by directly press-transferring a single-walled carbon nanotube (SWCNT) film. We fabricated Schottky diodes for photodetector applications using dry-transferred SWCNT films as the transparent electrode to increase light absorption in photoactive MoS2 channels. The MoS2 flake vertically stacked with an SWCNT electrode can exhibit excellent photodetection performance with a responsivity of ∼2.01 × 103 A/W and a detectivity of ∼3.2 × 1012 Jones. Additionally, we carried out temperature-dependent current-voltage measurement and Fowler-Nordheim (FN) plot analysis to explore the dominant charge transport mechanism. The enhanced photodetection in the vertical configuration is found to be attributed to the FN tunneling and internal photoemission of charge carriers excited from indium tin oxide across the MoS2 layer. Our study provides a novel concept of using a photoactive MoS2 layer as a tunneling layer itself with a dry-transferred transparent SWCNT electrode for high-performance and energy-efficient optoelectronic devices.

Role of deposition parameters on the properties of the fabricated heterojunction ZnS/p-Si Schottky diode

Heterojunction diodes of ZnS/p-Si have been fabricated using the chemical bath deposition (CBD) technique at two different deposition durations under both stirring and non-stirring conditions. The x-ray diffraction (XRD) patterns indicate the deposited ZnS films exhibit good crystallinity with the growth direction along the (111) planes of a cubic zinc blend structure. The crystallite size of all the deposited ZnS thin films have been calculated using the Scherer formula and found to be in the range of 2.2–2.7 nm which is very close (∼4 nm) to the size estimated using transmission electron microscopy (TEM). The surface morphology of the deposited ZnS thin films were studied by scanning electron microscopy (SEM) and it was observed that spherical nanoparticles agglomerated with the increase in deposition time. Furthermore, the optical properties of the deposited ZnS thin films were studied using UV-visible (UV-VIS) and photoluminescence (PL) spectroscopy. The effective calculated band gap was found in the range from 3.7–3.82 eV for all the samples, however PL spectra shows multiple emissions in the as-deposited ZnS films, indicating the presence of intrinsic defects, The characteristics of the fabricated ZnS/p-Si heterojunction diode was studied by measuring the dark current-voltage (I–V) relation using thermionic emission model. Electrical parameters such as barrier height, saturation current, ideality factor and series resistance were extracted from the I–V characteristics of the fabricated Schottky diodes. The barrier potential for all the ZnS/p-Si heterojunction diodes range between 0.829–0.857. Moreover, the calculated ideality factor was found very close to the ideal value of the diode (1.34 and 1.43) in the devices fabricated under stirring conditions.

Schottky diode characteristics on high-growth rate LPCVD β -Ga2O3 films on (010) and (001) Ga2O3 substrates

High crystalline quality thick β-Ga2O3 drift layers are essential for multi-kV vertical power devices. Low-pressure chemical vapor deposition (LPCVD) is suitable for achieving high growth rates. This paper presents a systematic study of the Schottky barrier diodes fabricated on four different Si-doped homoepitaxial β-Ga2O3 thin films grown on Sn-doped (010) and (001) β-Ga2O3 substrates by LPCVD with a fast growth rate varying from 13 to 21 μm/h. A higher temperature growth results in the highest reported growth rate to date. Room temperature current density–voltage data for different Schottky diodes are presented, and diode characteristics, such as ideality factor, barrier height, specific on-resistance, and breakdown voltage are studied. Temperature dependence (25–250 °C) of the ideality factor, barrier height, and specific on-resistance is also analyzed from the J–V–T characteristics of the fabricated Schottky diodes.

α-Gallium Oxide Films on Microcavity-Embedded Sapphire Substrates Grown by Mist Chemical Vapor Deposition for High-Breakdown Voltage Schottky Diodes.

α-Gallium oxide, with its large band gap energy, is a promising material for utilization in power devices. Sapphire, which has the same crystal structure as α-Ga2O3, has been used as a substrate for α-Ga2O3 epitaxial growth. However, lattice and thermal expansion coefficient mismatches generate a high density of threading dislocations (TDs) and cracks in films. Here, we demonstrated the growth of α-Ga2O3 films with reduced TD density and residual stress on microcavity-embedded sapphire substrates (MESS). We fabricated the two types of substrates with microcavities: diameters of 1.5 and 2.2 μm, respectively. We confirmed that round conical-shaped cavities with smaller diameters are beneficial for the lateral overgrowth of α-Ga2O3 crystals with lower TD densities by mist chemical vapor deposition. We could obtain crack-free high-crystallinity α-Ga2O3 films on MESS, while the direct growth on a bare sapphire substrate resulted in an α-Ga2O3 film with a number of cracks. TD densities of α-Ga2O3 films on MESS with 1.5 and 2.2 μm cavities were measured to be 1.77 and 6.47 × 108 cm-2, respectively. Furthermore, cavities in MESS were certified to mitigate the residual stress via the redshifted Raman peaks of α-Ga2O3 films. Finally, we fabricated Schottky diodes based on α-Ga2O3 films grown on MESS with 1.5 and 2.2 μm cavities, which exhibited high breakdown voltages of 679 and 532 V, respectively. This research paves the way to fabricating Schottky diodes with high breakdown voltages based on high-quality α-Ga2O3 films.

Effects of Fermi pinning and quantum mechanisms on leakage current of 4H-SiC Schottky diodes

Reverse bias leakage current through 4H-SiC Schottky diodes was modeled using quantum transmission theory and the theoretically calculated values were compared with the measured values from fabricated Schottky diodes. To account for interface defects, energy barriers due to Fermi pinning from previously observed defects were used in place of the ideal barrier structure predicted by the Schottky–Mott rule. Incorporating barriers with energy values set due to Fermi pinning at known defect energies resulted in better experimental agreement by many orders of magnitude.

Synthesis of n-type ZrO2 doped ε-Ga2O3 thin films by PLD and fabrication of Schottky diode

Tin-assisted pure phase n-type ZrO2-doped ε-Ga2O3 films were synthesized by pulsed laser deposition (PLD) and deposited on (0001) epi-GaN/sapphire substrates. The characterization of n-type ZrO2-doped ε-Ga2O3 thin films and the electrical properties of SBD based on that film were investigated in details. From XRD, the pure Zr-doped ε-Ga2O3 without diffraction peaks of zirconia suggested the formation of ε-(ZrxGa1−x)2O3 solid solution. The surface morphology and chemical content of the ε-Ga2O3 thin film were studied by AFM and XPS. The electrical resistivity and related free carrier concentration at room temperature were measured to be 108 Ω·cm and 5.5 × 1015 cm−3, respectively, and mobility up to 10.3 cm2/V·s. The Schottky barrier diode possessed a rectification ratio up to 106~107, breakdown voltage of 392 V, and the interface states density from 2.4 × 1013 cm-2 eV-1 to 6.4 × 1014 cm-2 eV-1 with the trap energy level from 0.89 eV to 0.94 eV below the bottom of the conduction band.

WSe2/Pd Schottky diode combining van der Waals integrated and evaporated metal contacts

Metal–semiconductor junctions are at the heart of modern electronics. Various two-dimensional materials (2D) based electronic devices have been reported. However, Ohmic contacts between evaporated metal contacts and semiconducting 2D materials are still hard to achieve. Thus, design and fabrication of Schottky diodes based on layered WSe2 remain challenging. Here, we report a doping-free strategy to achieve Ohmic contacts in WSe2 diodes via van der Waals (vdW) contacts. We designed and fabricated vertical WSe2/Pd Schottky diodes, in which Ohmic and Schottky junctions can be realized simultaneously via vdW contacts and evaporated contacts, respectively. The specific contact resistance of the vdW contact is about 74.5 kΩ·μm2. The Schottky diodes exhibit strong rectification behavior with rectification ratio up to 105.

Studies on Schottky Barrier Diodes Fabricated using Single‐Crystal Wafers of β‐Ga2O3 Grown by the Optical Floating Zone Technique

β‐Ga2O3 is one of the most promising wide‐bandgap materials for optoelectronic applications as well as a conducting substrate for GaN‐based device technologies. Single crystals of undoped β‐Ga2O3 are grown by the optical floating zone technique utilizing compressed dry air as growth atmosphere. The properties of β‐Ga2O3 are highly anisotropic. Optimization of the processing recipe for wafers along different orientations suitable for device development is conducted. Structural, optical, and electrical properties of the wafers are determined. Efforts are made to fabricate Schottky diodes based on Pt/Ti/Au–β‐Ga2O3–Ti/Au device structures. Devices are fabricated on (−201) cut wafers. The device characteristics are discussed in detail.

ELECTRICAL AND PHOTOELECTRIC PROPERTIES OF SCHOTTKY DIODES GRAPHITE/n-Si PREPARED BY THE PENCIL-ON-SEMICONDUCTOR METHOD

This paper reports the results of an investigation of electrical properties photosensitive Schottky diodes graphite/n-Si prepared for the first time by the transfer of dry drawn graphite films onto single crystal n-Si. Barrier parameters were determined and C-V characteristics was studied. The dominating mechanisms of current transfer through the heterojunction have been determined: at forward bias is well described within of tunneling-recombination models via surface states at the graphite/n-Si interface, at reverse bias was determined to be the small current flows through the shunt resistance. It was found that under illumination with white light with an intensity Popt = 80 mW/cm2, the reverse current Ilight increases by more than an order of magnitude in comparison with its value in the dark Idark due to the separation of photogenerated electron-hole pairs. From the above, it can be conclude that the fabricated Schottky diodes can be use as a photosensitive device.

Enhanced solar-cell efficiency via fabricated zinc sulfide nanocrystalline thin film-based Schottky diodes as a bypass: An experimental and theoretical investigations

This work represents experimental and theoretical investigations on the electrical characteristics of ZnS nanocrystalline thin films synthesized via sonicated (UCBD) and un-sonicated (CBD) chemical bath deposition technique and the fabrication of Schottky junction diodes, for potential solar cell incorporation and other opto-electronic applications. The sonication induced ZnS nanocrystalline thin films (SNP) at frequency 20 kHz–1 MHz and without sonication induced ZnS nanocrystalline thin films (NP) deposited on an indium tin oxide (ITO) substrate. A rapid thermally evaporated lightly doped Ag on SNP and NP-ZnS transparent thin films in the high range of vacuum (~10−6 Torr), has been achieved. The current density-voltage (J-V) and capacitance-voltage (C-V) measurements of fabricated Schottky diodes were carried out employing a potentiostat device. The enhanced performance of fabricated Schottky devices has been quantified by analyzing their J-V characteristics using established Landauer transport formalism. Ideal diode behavior has been confirmed by a low voltage drop of 0.35 V, and low junction capacitance ~3.21 nF across fabricated Schottky diodes. The maximum blockage of leakage current across fabricated Schottky diodes have been detected as compared to the available commercial diodes. The Landauer transport model found to be excellent fitting for understanding the electron transport mechanism for these fabricated diodes. The Fermi energy level pinned near effective gap center that shifts under the bias condition due to the metal induced gap states. The Schottky diodes as a bypass in solar cell panel demonstrates the significant enhancement in photo-response and efficiency of solar cell in the presence of sunlight.

Observation of in situ enhanced crystallization, negative resistance effect and photosensitivity in Tl2InGaSe4 crystals

In this work, we report the properties of Tl2InGaSe4 crystals as multifunctional material. Namely, Tl2InGaSe4 crystals are grown by the modified Bridgman method using mixtures of TlInSe2 (50%) and TlGaSe2 (50%) single crystals. The enhanced crystallization and structural stabilities are monitored by the X-ray diffraction technique during the in situ heating and cooling cycles. The structural analyses on the Tl2InGaSe4 crystals revealed domination of both of the monoclinic and tetragonal phases in the crystals. In addition, the produced crystals are used to fabricate Schottky diodes. While the scanning electron microscopy has shown that the crystals are composed of layered nanosheets, the electrical analyses have shown that the crystals exhibit light photosensitivity of 12.7 under tungsten light illumination of 10 kLuxes. The attenuation in the electrical parameters of the Ag/Tl2InGaSe4/C diodes presented by series resistance, barrier height and ideality factor upon light excitations make them promising for applications in optoelectronics as switches and photodetectors. Moreover, the alternating electrical signals analyses on the capacitance spectra displayed resonance –antiresonance oscillations in the frequency domain of 83–100 MHz. The resistance spectra also exhibited negative resistance effect in the range of 55–135 MHz. These features of the device make it suitable for use as microwave resonators and memory devices as well.

Fabrication, Characterization and Simulation of Sputtered Pt/In-Ga-Zn-O Schottky Diodes for Low-Frequency Half-Wave Rectifier Circuits

Amorphous In-Ga-Zn-O (IGZO) is a high-mobility semiconductor employed in modern thin-film transistors for displays and it is considered as a promising material for Schottky diode-based rectifiers. Properties of the electronic components based on IGZO strongly depend on the manufacturing parameters such as the oxygen partial pressure during IGZO sputtering and post-deposition thermal annealing. In this study, we investigate the combined effect of sputtering conditions of amorphous IGZO (In:Ga:Zn=1:1:1) and post-deposition thermal annealing on the properties of vertical thin-film Pt-IGZO-Cu Schottky diodes, and evaluated the applicability of the fabricated Schottky diodes for low-frequency half-wave rectifier circuits. The change of the oxygen content in the gas mixture from 1.64% to 6.25%, and post-deposition annealing is shown to increase the current rectification ratio from 10 5 to 10 7 at ±1 V, Schottky barrier height from 0.64 eV to 0.75 eV, and the ideality factor from 1.11 to 1.39. Half-wave rectifier circuits based on the fabricated Schottky diodes were simulated using parameters extracted from measured current-voltage and capacitance-voltage characteristics. The half-wave rectifier circuits were realized at 100 kHz and 300 kHz on as-fabricated Schottky diodes with active area of 200 μm × 200 μm, which is relevant for the near-field communication (125 kHz - 134 kHz), and provided the output voltage amplitude of 0.87 V for 2 V supply voltage. The simulation results matched with the measurement data, verifying the model accuracy for circuit level simulation.

Tunable Surface Plasmon Polaritons with Monolithic Schottky Diodes

Surface plasmon polaritons (SPPs) provide subwavelength electric field confinement ranging from microwave to the visible. Several approaches have been explored to manipulate SPPs with a typical modulation capability of only a few percent. Here, active control of SPPs using monolithically fabricated Schottky diodes has been first designed and realized, achieving a continuous and significant modulation of transmission, reflection, and absorption. The SPPs propagating on a metal line are attenuated by using split ring resonators (SRRs) with an In–Ga–Zn–O Schottky diode bridging each SRR split gap. The resistance of the diodes can be tuned over a range of a few orders of magnitude with bias voltage, which continuously transforms each SRR to a metallic quasi-loop with subdued resonance. A remarkable modulation of 40% and 19% was demonstrated for the transmission and absorption, respectively, which to the best of our knowledge has not been achieved before.

Influence (Ce and Sm) co-doping ZnO nanorods on the structural, optical and electrical properties of the fabricated Schottky diode using chemical bath deposition

Schottky diodes based on ZnO nanorods, undoped and co-doped with different concentrations (0.0, 0.2, 0.4, 0.6 and 0.8 at.%) of Ce and Sm, were fabricated on glass and on n-Si (111) substrates using chemical bath deposition assisted with the sol-gel spin coating. The ZnO maintained its hexagonal shape up to higher levels of doping (0.8 at.%) with the growth rate being suppressed by Ce and Sm co-doping. The as-synthesized nanorods were found to be highly crystalline and no impurities or peaks related to Ce and Sm or their oxides were observed. Room temperature Raman spectroscopy revealed that the prominent E2 high peak shifted towards a lower wave number and the intensity decreased upon doping. X-ray photoelectron spectroscopy studies at room temperature showed that the presence of Zn and O in all samples with small amounts of Ce and Sm being detected at doping levels of 0.8 at.%. Photoluminescence studies at room temperature revealed a weak ultraviolet emission and a strong deep level (visible) emission. Deconvolution of the visible emission spectra showed that more than one defect contributed to the visible emission. The I–V characteristics of the fabricated Schottky diode devices measured at room temperature showed that the Ce and Sm co-doping increased the generation-recombination process in the fabricated Schottky diodes. Furthermore, the current transport mechanism in the fabricated Schottky devices at a lower voltage (0.0–∼ 0.6 V) was dominated by ohmic conduction mechanism, while at voltages greater than 0.6 V, the space charge limited current and the trap filled limit voltage mechanism dominated.

Effect of (Ce, Al) co-doped ZnO thin films on the Schottky diode properties fabricated using the sol-gel spin coating

In this work, Schottky diodes based on undoped and (Ce, Al) co-doped ZnO thin films have been fabricated using the sol-gel spin coating. The effect of (Ce, Al) co-doped ZnO films on the structural and optical properties has been studied, and the electrical characteristic of the fabricated Schottky diode devices are investigated. X-ray diffraction and field emission scanning electron microscopy are used to study the crystalline structure and surface morphology, respectively. Room temperature Raman spectroscopy showed that the intensity of the dominant E2 high peak decreased after doping. The photoluminescence studies at room temperature showed that the intensity of the UV and the visible emission peak decreased after doping. UV-vis spectroscopy measurements at room temperature showed a decrease in the optical band gap after doping compared to undoped ZnO thin films. The I–V characteristics of fabricated Schottky diodes manifest good device behaviour at higher levels of doping (7.0 at.%) with an ideality factor of 2.40, the barrier height of 0.77 eV and series resistance of 262 Ω. The maximum rectification ratio was found to be nearly 105 at 7.0 at.%. Moreover, the electrical properties of the Schottky diode devices analyzed with Cheung-Cheung function revealed that the Schottky diode parameters were higher compared to those obtained from the conventional thermionic emission theory. Furthermore, the free electron carrier concentration for the doped samples was found to be lower compared with undoped ZnO films.