High Schottky Barrier Research Articles

All‐Electronic Memristor Based on Charge Carrier Confinement in Bulk Semiconductor of Metal–Semiconductor–Metal Structure

AbstractMemristors have gained significant attention in recent years due to their potential applications in computing and memory technology by offering higher performance, lower power consumption, and increased storage capacity. In this paper, a new type of volatile memristor is presented by analyzing the dynamic behavior of charge carriers within a metal–semiconductor–metal (MSM) structure. It is shown that an all‐electronic memristor is achieved through the confinement of majority charge carriers within the bulk semiconductor by the favor of high barrier Schottky contacts. The findings reveal a remarkable current offset between forward and backward scans, along with exceptional current pulse consistency with a tunable current level using pulse frequency. These characteristics greatly simplify the process of designing electrical circuits incorporating this memristor variant. Furthermore, this research paves the way for the development of crystalline semiconductor‐based memristors. While various semiconductors with controllable doping densities can be considered as potential candidates for this type of memristor, the calculations using silicon demonstrate the integration of this semiconductor with the current technology holds significant promise for two terminal memristors.

Optimizing Forward Drop and Reverse Leakage Trade‐Off in AlGaN/GaN Lateral Diode with Schottky‐Metal‐Insulator‐Semiconductor Cascode Anode

Herein, AlGaN/GaN lateral diode with the Schottky‐Metal‐Insulator‐Semiconductor (MIS) cascode anode (CALD) to optimize forward voltage drop (VF) and reverse leakage current (ILEAK) trade‐off is proposed. In the CALD device, a normally‐on Ni/HfO2/AlGaN MIS‐controlled channel as well as a lateral Ni/GaN Schottky contact are cascoded at the anode. The designed normally‐on MIS‐controlled channel has high electron concentration at forward bias and prevents high electric‐field at reverse bias, which ensure both low VF and low ILEAK. Meanwhile, the Ni/GaN Schottky contact with a high Schottky barrier height further suppresses the ILEAK. As a result, the fabricated CALD demonstrates an optimized VF–ILEAK trade‐off relationship, including a low VF of 1.6 V and a low ILEAK of 5.2 × 10−8 A mm−1 (at reverse voltage of 400 V), together with a high breakdown voltage (BV) >700 V. These high performances suggest that the CALD can be a promising candidate for GaN power diode applications requiring a better VF–ILEAK trade‐off.

Strategy to enhance the performance of spin field effect transistors-insert effective intermediate layer graphene

Abstract Novel spin field effect transistors (FETs) with metal contacts are designed to reduce the high Schottky barrier height (SBH) due to Fermi pinning, reducing energy consumption and increasing their performance. Herein, we effectively enhance the conductivity (106 orders of magnitude) and current threshold of the FETs by introducing interlayer graphene in the contact interface between the semiconductor blue phosphorus and the metal, thereby reducing the interlayer resistance. Electronic structure analysis shows that Blue Phosphorus–Graphene–Cu modulates the lowest SBH, yielding a larger FETs conductance compared to other metal systems. The spin injection further enhances the efficiency of FETs as rectifiers (enhanced 13%). This theoretical work provides rational guidance for realizing innovations in next-generation high-performance transistor technology, demonstrating the inherent potential of the regulatory mechanism.

Ohmic Contact Resistance in SiC Diodes with Ti and NiSi P<sup>+</sup> Contacts

Ohmic contacts play a major role in the signal transfer between the semiconductor device and the external circuitry. One of the main technological issues to develop high-performance SiC-based devices is the control of metal/SiC contact properties to fabricate low resistance and high stability SiC Ohmic contacts to p-type SiC. This is mostly due to intrinsic SiC characteristics like large work function, low dopant activation for p-type materials and low hole mobility. These limits are even more emphasized in SiC JBS or MPS diodes, where Schottky and Ohmic contacts on the P doped regions embedded in the active area to improve surge ruggedness are usually formed by using the same metallization process. This naturally results either in a high Schottky barrier height in the Schottky contact with consequent increase of the conduction loss at low currents or in a poorly conductive Ohmic contact, leading to reduced IFSM capability. Therefore, the optimization and control of the process parameters like for example the P+ doping concentration peak underneath the metallization layer and the annealing process temperatures is crucial to obtain a good Ohmic contact and enhance the device´s robustness against surge current.

Wide bandgap semiconductors for radiation detection in extreme conditions

High barrier Schottky diodes offer potential for increased efficiency without current leakage.

The Influence of Au Loading and TiO2 Support on the Catalytic Wet Air Oxidation of Glyphosate over TiO2+Au Catalysts

This study aimed to explore the impact of varying amounts of added Au (0.5 to 2 wt.%) and the structural characteristics of anatase TiO2 supports (nanoparticles (TP, SBET = 88 m2/g) and nanorods (TR, SBET = 105 m2/g)) on the catalytic efficiency of TiO2+Au catalysts in eliminating the herbicide glyphosate from aqueous solutions via the catalytic wet air oxidation (CWAO) process. The investigation was conducted using a continuous-flow trickle-bed reactor. Regardless of the TiO2 support and the amount of Au added, the addition of Au has a positive effect on the glyphosate degradation rate. Regarding the amount of Au added, the highest catalytic activity was observed with the TP + 1% Au catalyst, which had a higher Schottky barrier (SB) than the TP + 2% Au catalyst, which helped the charge carriers in the TiO2 conduction band to increase their reduction potential by preventing them from returning to the Au. The role of glyphosate degradation product adsorption on the catalyst surface is crucial for sustaining the long-term catalytic activity of the investigated TiO2+Au materials. This was particularly evident in the case of the TR + 1% Au catalyst, which had the highest glyphosate degradation rate at the beginning of the CWAO experiment, but its catalytic activity then decreased over time due to the adsorption of glyphosate degradation products, which was favoured by the presence of strong acidic sites. In addition, the TR + 1% Au solid had the smallest average Au particle size of all analyzed materials, which were more easily deactivated by the adsorption of glyphosate degradation products. The analysis of the degradation products of glyphosate shows that the oxidation of glyphosate in the liquid phase involves the rupture of C–P and C–N bonds, as amino-methyl-phosphonic acid (AMPA), glyoxylic acid and sarcosine were detected.

Over 600 V Lateral AlN-on-AlN Schottky Barrier Diodes with Ultra-Low Ideality Factor

This letter reports the demonstration of lateral AlN Schottky barrier diodes (SBDs) on single-crystal AlN substrates by metalorganic CVD (MOCVD) with an ultra-low ideality factor (η) of 1.65, a high Schottky barrier height of 1.94 eV, a breakdown voltage (BV) of 640 V, and a record high normalized BV by the anode-to-cathode distance. The device current was dominated by thermionic emission, while most previously reported AlN SBDs suffered from defect-induced current with higher η (>4). This work represents a significant step towards high-performance ultra-wide bandgap AlN-based high-voltage and high-power devices.

Bismuth as a buffer layer for metal contact with silicon carbide studied by In situ photoelectron spectroscopy

Silicon carbide (SiC) is a promising third-generation semiconductor due to its wide bandgap. However, the high Schottky barrier and metal-induced gap states (MIGS) at the metal/SiC interface present significant challenges for device fabrication, leading to high contact resistance and poor current delivery. This study proposes the use of bismuth (Bi), with its semimetallic properties and gap-state saturation effect, as a contact buffer layer to address these issues. We conducted a systematic investigation of the chemical and electronic characteristics of the Pt/Bi/4H-SiC(0001) system, fabricated via molecular beam epitaxy (MBE), using in situ X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). Our findings reveal weak bonding between the Bi buffer layer and the 4H-SiC(0001) surface, resulting in a slight downward band bending effect and the formation of a substantial dipole across the Bi/4H-SiC(0001) interface. Moreover, UPS spectra indicate a reduction in the work function of Pt/Bi/4H-SiC(0001), suggesting the potential for achieving low contact resistance. Notably, the Pt/Bi/4H-SiC(0001) system remains stable when exposed to 1.6×109 Langmuir of oxygen at room temperature, while a bare Bi buffer layer undergoes partial oxidation. These results provide a comprehensive understanding of the Pt/Bi/4H-SiC(0001) interfaces and strategies for improving metal/SiC contacts.

Ga2O3/NiO junction barrier Schottky diodes with ultra-low barrier TiN contact

Power Schottky barrier diodes (SBDs) face an inherent trade-off between forward conduction loss and reverse blocking capability. This limitation becomes more severe for ultra-wide bandgap (UWBG) SBDs due to the large junction field. A high Schottky barrier is usually required to suppress the reverse leakage current at the price of an increased forward voltage drop (VF). This work demonstrates a Ga2O3 junction barrier Schottky (JBS) diode that employs the embedded p-type NiO grids to move the peak electric field away from the Schottky junction, thereby allowing for the use of an ultra-low barrier TiN Schottky contact. This JBS diode concurrently realizes a low VF of 0.91 V (at forward current of 100 A/cm2) and a high breakdown voltage over 1 kV, with the VF being the lowest in all the reported vertical UWBG power diodes. Based on the device characteristics measured up to 200 °C, we further analyze the power loss of this JBS diode across a wide range of operational duty cycles and temperatures, which is found to outperform the TiN/Ga2O3 SBDs or NiO/Ga2O3 PN diodes. These findings underscore the potential of low-barrier UWBG JBS diodes for high-frequency, high-temperature power electronics applications.

CVD graphene contacts for lateral heterostructure MoS2 field effect transistors

Intensive research has been carried out on two-dimensional materials, in particular molybdenum disulfide, towards high-performance field effect transistors for integrated circuits1. Fabricating transistors with ohmic contacts is a challenging task due to the formation of a high Schottky barrier that severely limits the performance of the transistors for real-world applications. Graphene-based heterostructures can be used in addition to, or as a substitute for unsuitable metals. In this paper, we present lateral heterostructure transistors made of scalable chemical vapor-deposited molybdenum disulfide and chemical vapor-deposited graphene achieving a low contact resistances of about 9 kΩ·µm and high on/off current ratios of 108. Furthermore, we also present a theoretical model calibrated on our experiments showing further potential for scaling transistors and contact areas into the few nanometers range and the possibility of a substantial performance enhancement by means of layer optimizations that would make transistors promising for use in future logic integrated circuits.

Low turn-on voltage and 2.3 kV β -Ga2O3 heterojunction barrier Schottky diodes with Mo anode

In this work, we propose combining a low work function anode metal and junction barrier Schottky structure to simultaneously achieve low turn-on voltage (Von) and high breakdown voltage (BV), which alleviates the dilemma that high BV requires high Schottky barrier height (SBH) and high Von. Molybdenum (Mo) is used to serve as the anode metal to reduce the SBH and facilitate fast turn-on to achieve a low Von. To resolve the low SBH related low BV issue, a p-NiO/n-Ga2O3-based heterojunction structure is used to enhance β-Ga2O3 sidewall depletion during the reverse state to improve the BV. With such a design, a low Von = 0.64 V(@1A/cm2) and a high BV = 2.34 kV as well as a specific on-resistance (Ron,sp) of 5.3 mΩ cm2 are demonstrated on a 10 μm-drift layer with a doping concentration of 1.5 × 1016 cm−3. β-Ga2O3 JBS diodes with low Von = 0.64 V and a power figure of merit of 1.03 GW/cm2 show great potential for future high-voltage and high-efficiency power electronics.

Investigation on Contact Properties of 2D van der Waals Semimetallic 1T-TiS2/MoS2 Heterojunctions.

Two-dimensional transition metal dichalcogenides (2D TMDCs) are considered promising alternatives to Si as channel materials because of the possibility of retaining their superior electronic transport properties even at atomic body thicknesses. However, the realization of high-performance 2D TMDC field-effect transistors remains a challenge owing to Fermi-level pinning (FLP) caused by gap states and the inherent high Schottky barrier height (SBH) within the metal contact and channel layer. This study demonstrates that high-quality van der Waals (vdW) heterojunction-based contacts can be formed by depositing semimetallic TiS2 onto monolayer (ML) MoS2. After confirming the successful formation of a TiS2/ML MoS2 heterojunction, the contact properties of vdW semimetal TiS2 were thoroughly investigated. With clean interfaces of the TiS2/ML MoS2 heterojunctions, atomic-layer-deposited TiS2 can induce gap-state saturation and suppress FLP. Consequently, compared with conventional evaporated metal electrodes, the TiS2/ML MoS2 heterojunctions exhibit a lower SBH of 8.54 meV and better contact properties. This, in turn, substantially improves the overall performance of the device, including its on-current, subthreshold swing, and threshold voltage. Furthermore, we believe that our proposed strategy for vdW-based contact formation will contribute to the development of 2D materials used in next-generation electronics.

β-Ga2O3 Schottky Barrier Diode with Ion Beam Sputter-Deposited Semi-Insulating Layer

Vertical Schottky barrier diodes based on an ion beam sputter (IBS)-deposited β-Ga2O3 film on a single-crystalline (2¯01) unintentionally doped (UID) β-Ga2O3 with a Ni contact were developed. To form ohmic Ti/Ni contacts, the IBS-Ga2O3/UID β-Ga2O3 structures were wet-etched, and an indium tin oxide (ITO) intermediate semiconductor layer (ISL) was deposited on the opposite surface of the UID β-Ga2O3. The IBS-deposited Ga2O3 layer was polycrystalline and semi-insulating. Low leakage currents, rectification ratios of 3.9 × 108 arb. un. and 3.4 × 106 arb. un., ideality factors of 1.43 and 1.24, Schottky barrier heights of 1.80 eV and 1.67 eV as well as breakdown voltages of 134 V and 180 V were achieved for diodes without and with ITO-ISL, respectively. The surface area of the IBS-Ga2O3 film acted as a thin dielectric layer and, together with the preliminary wet etching, provided low leakage currents and relatively high Schottky barrier heights. Diodes with a Schottky barrier based on a Ni/IBS-deposited Ga2O3 film contact were demonstrated for the first time.

Contact engineering for 2D Janus MoSSe/metal junctions.

The flourish of two-dimensional (2D) materials provides a versatile platform for building high-performance electronic devices in the atomic thickness regime. However, the presence of the high Schottky barrier at the interface between the metal electrode and the 2D semiconductors, which dominates the injection and transport efficiency of carriers, always limits their practical applications. Herein, we show that the Schottky barrier can be controllably lifted in the heterostructure consisting of Janus MoSSe and 2D vdW metals by different means. Based on density functional theory calculations and machine learning modelings, we studied the electrical contact between semiconducting monolayer MoSSe and various metallic 2D materials, where a crossover from Schottky to Ohmic/quasi-Ohmic contact is realized. We demonstrated that the band alignment at the interface of the investigated metal-semiconductor junctions (MSJs) deviates from the ideal Schottky-Mott limit because of the Fermi-level pinning effects induced by the interface dipoles. Besides, the effect of the thickness and applied biaxial strain of MoSSe on the electronic structure of the junctions are explored and found to be powerful tuning knobs for electrical contact engineering. It is highlighted that using the sure-independence-screening-and-sparsifying-operator machine learning method, a general descriptor WM3/exp(Dint) was developed, which enables the prediction of the Schottky barrier height for different MoSSe-based MSJ. These results provide valuable theoretical guidance for realizing ideal Ohmic contacts in electronic devices based on the Janus MoSSe semiconductors.

High DC-Bias Stability and Reliability in BaTiO3-Based Multilayer Ceramic Capacitors: The Role of the Core-Shell Structure and the Electrode.

With the miniaturization of multilayer ceramic capacitors (MLCCs) and the increase of the electric field on a single dielectric layer, dielectric constant DC-bias stability and reliability have gradually aroused attention in the advanced electronics industry. In this study, MLCCs with outstanding DC-bias stability and reliability were prepared by using dielectric ceramic optimization and electrode optimization strategies. The effect of the Dy-Y doping concentration on the microstructure, dielectric properties, and reliability of BaTiO3-based ceramics was investigated. The shell ratio and effective shell doping concentration of the core-shell structure in ceramic grains play important roles in defects and electrical performances. The ceramic with appropriate doping contents shows a dielectric constant of 1800 and a dielectric constant change rate of -17% under a DC field of 4 kV/mm, which was fabricated into prototype MLCCs with different Ni electrodes. MLCCs exhibit outstanding DC-bias stability with a -28% degradation in the dielectric constant under a DC field of 4 kV/mm while possessing a dielectric constant of 2300 and satisfying the EIA X7S specification. Additionally, it was discovered that MLCCs prepared by using fine-size Ni particle electrodes have low electrode roughness and high interfacial Schottky barriers, resulting in better reliability. This study provides promising candidate materials and theoretical references for high-end and high DC-bias stability MLCCs.

(Invited) Characterization of Metal/GaN Schottky Contacts - Review from the Early Days

GaN-based materials have been intensively developed for blue light-emitting-diodes, blue laser diodes, power amplifiers in wireless base-stations, and high-power switching devices. Schottky contacts are one of the most important components in electron device fabrication. The electrical characteristics of GaN Schottky barrier contacts have been continuously studied for more than twenty years as improvement of GaN crystal quality and understanding physics of metal/semiconductor interfaces.In the early days, for the achievement of the high-power and high-temperature operation, thermally stable contacts were explored. Interfacial reactions and electrical characteristics were intensively examined by annealing studies for various kinds of metal contacts such as Ni, Pd, Pt, and Re. As a result of those, Ni has been widely used as a stable Schottky contact, because less thermal reaction with N atoms, high Schottky barrier height (qφ B), and good adhesion.As for the correlation with GaN crystal quality, in the early days, because a GaN epitaxial layer contained large-structure killer defects, rectifying characteristics were hardly observed in the Schottky contacts. Since after the n-GaN crystal quality improved with electron mobility over 100 cm2V−1 s−1, rectifying characteristics have been reproducibly obtained.[1] Even though the dislocation density was as high as 109–1010 cm−2 in epitaxial GaN layers, good current–voltage (I–V) characteristics and qφ B values below 1.1 eV were reported in Ni/n-GaN contacts. Moreover, in order to clarify the effect of dislocations on I–V characteristics, a 0.5-µm-diameter Schottky-dot array was formed on n-GaN grown by MOCVD, and I –V measurements were conducted using AFM with a conductive probe.[2] Neither mixed nor pure edge dislocations affected the I –V characteristics, but a large structural defect with a diameter of a few hundred nanometers shorted the contact.In addition, further improvement of the GaN layer grown on low dislocation (∼106 cm−2) free-standing GaN substrates provided ideal Schottky contacts with high qφ B values around 1.1 eV. It has been reported that the forward and reverse I–V characteristics of Ni contacts formed on hydride-vapor-phase-epitaxy grown n-GaN obeyed the thermionic emission and the thermionic field emission (TFE) models, respectively.[3] The same trend was also reported in nine different metal contacts on both c- and cleaved m-plane n-GaN crystals.[4] We also reported a post-metallization annealing at 400°C for 10 min was effective to reduce the reverse biased current significantly to the prediction by the TFE model.[5]Basic understanding of p-GaN Schottky contacts was slower than that of n-GaN, because p-GaN contacts were intensively studied for ohmic contacts of p-n-junction-base optical devices. In the early days, very leaky characteristics were reported and a reasonable qφ B value was not obtained. We improved leaky characteristics of Ni/p-GaN Schottky contacts by low Mg doping. The qφ B as high as 2.4 eV and the n-values of 1.8 were obtained from I –V.[6] We found a memory effect that carrier capture and emission from acceptor-like deep level defects caused depletion layer width to vary significantly.[7]Finally, as our original technique, scanning internal photoemission spectroscopy was developed to map the electrical characteristics of metal/semiconductor interfaces nondestructively.[8] We have demonstrated the mapping of characteristics for interfacial reactions of Ni/n-GaN at 400°C; degradation under applied voltage stress up to 45 V for vertical n-GaN contacts; and process induced surface damages by ion-implantation, dry etching, and photo-electrochemical etching.[9] This technique was confirmed to be useful for the development of the wide-bandgap-semiconductor high-power devices. K. Shiojima, J. Woodall, P. Grudowski, C. Eiting and R. Dupuis, J. Vac. Sci. Tech., B17(5), p. 2030 (1999).K. Shiojima, and T. Suemitsu, J. Vac. Scie. Tech., B21(2) p. 698(2003).J. Suda, K. Yamaji, Y. Hayashi, T. Kimoto, K. Shimoyama, H. Namita, and S. Nagao, Appl. Phys. Express, 3, p. 101003 (2010).H. Imadate, T. Mishima, and K. Shiojima, Jpn. J. Appl. Phys., 57, p. 04FG13 (2018).K. Shiojima, R. Tanaka, S. Takashima, K. Ueno, and M. Edo, Jpn. J. Appl. Phys., 60, 056503 (2021).K. Shiojima, T. Sugahara and S. Sakai, Appl. Phys. Lett., 74, p. 1936 (1999).K. Shiojima, T. Sugahara and S. Sakai, Appl. Phys. Lett. 77, p. 4353 (2000).T. Okumura and K. Shiojima, Jpn. J. Appl. Phys., vol. 28, p. L1108 (1989).K. Shiojima, ECS Transactions, 104, p. 69 (2021).

Realizing On/Off Ratios over 104 for Sub-2 nm Vertical Transistors.

Vertical transistors hold promise for the development of ultrascaled transistors. However, their on/off ratios are limited by a strong source-drain tunneling current in the off state, particularly for vertical devices with a sub-5 nm channel length. Here, we report an approach for suppressing the off-state tunneling current by designing the barrier height via a van der Waals metal contact. Via lamination of the Pt electrode on a MoS2 vertical transistor, a high Schottky barrier is observed due to their large work function difference, thus suppressing direct tunneling currents. Meanwhile, this "low-energy" lamination process ensures an optimized metal/MoS2 interface with minimized interface states and defects. Together, the highest on/off ratios of 5 × 105 and 104 are realized in vertical transistors with 5 and 2 nm channel lengths, respectively. Our work not only pushes the on/off ratio limit of vertical transistors but also provides a general rule for reducing short-channel effects in ultrascaled devices.

Surface evolution of Pt/MoO3/4H-SiC(0001) investigated by in situ near-ambient pressure X-ray photoelectron spectroscopy

Achieving effective Ohmic contact between SiC and metal electrodes remains a challenge due to the high Schottky barrier resulting from the large mismatch between the deep-lying valence band of SiC and Fermi level of metals. One promising approach to address this issue is to introduce a high-work-function interfacial layer between the metal and semiconductor. However, the interaction mechanisms of the inserted high-work-function interfacial layer between metal electrodes and the SiC substrate have been rarely studied systematically. In this work, layers of high-work-function molybdenum trioxide (MoO3) and platinum (Pt) were successively grown on the 4H-SiC(0001) surface via conventional physical vapour deposition (PVD). We investigated the chemical and electronic structure evolutions upon Pt deposition on MoO3/4H-SiC(0001) using in situ near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) and ultraviolet photoelectron spectroscopy (UPS). Subsequently, the evolutions of Pt/MoO3/4H-SiC(0001) system during annealing under ultra-high vacuum (UHV) or various gas phase environments (H2 and O2) were studied via in situ NAP-XPS and UPS. Our results reveal that Pt showed its thermal stability during the annealing process, while Mo presented its versatile chemical characteristics. These results depict a detailed chemical feature of the Pt/MoO3/4H-SiC(0001) system and help gain a better understanding about the impact of different environments on Pt/MoO3 interface.

Investigation of high-performance Schottky diodes on a Ga2O3 epilayer using Cu with high barrier height, high temperature stability and repeatability

This work reports on high-performance Schottky barrier diodes (SBDs) fabricated on Ga2O3 epilayers using Cu as Schottky contacts (SCs). The fabricated SBDs exhibited high Schottky barrier heights (SBHs) with values greater than 1.0 eV, near-unity ideality factors, and a high rectification ratio (RR) of 1012 at 300 K. Temperature-dependent current–voltage (I–V–T) and capacitance–voltage (C–V–T) measurements were performed up to 500 K. The SBHs’ , calculated from the IVT characteristics, initially increased with temperature and then decreased with near-unity ideality factors. The increase in with temperatures up to 410 K indicated the spatial inhomogeneity at the metal–semiconductor interface. The observed decrease in above 410 K indicated the enhancement of barrier homogeneity at higher temperatures (⩾410 K). The decrease in above 410 K and decrease in , calculated from the CVT characteristics, with increasing temperature were assigned to the bandgap narrowing of Ga2O3. The IVT measurements were repeated many times, and the SBDs exhibited excellent thermal stability and showed high SBHs >1.0 eV, a high RR, and near-unity ideality factors. All these findings were attributed to the formation of high-work-function copper oxide thin film at the interface between Cu and Ga2O3. X-ray diffraction and x-ray photoelectron spectroscopy revealed the formation of a thin layer of high-work-function copper oxide. These findings provide the possibility to fabricate an SC with a high and homogeneous barrier and thermal stability using cheap, abundant Cu material, enabling low-cost mass production of future power semiconductor devices based on oxide semiconductors.

Enhanced Specific Detectivity and UV-to-Visible Rejection-Ratio of Visible-Blind Metal–Semiconductor–Metal Photodetectors, Based on Epitaxial GaN/Si(111)

A very high specific detectivity and UV-to-visible rejection-ratio (UVRR) is reported for visible-blind metal–semiconductor–metal (MSM) photodetectors (PDs), fabricated with gallium nitride (GaN) on Si(111) epitaxial layers. Comprehensive analysis of different figures-of-merit (FOM) reveals that the high specific detectivity results from a large responsivity in the UV-A region of the electromagnetic spectrum, and extremely low dark current, of the PDs. The current transport mechanisms in the absence and presence of illumination suggest that an internal gain, which is attributable to photo-induced barrier lowering, is responsible for the large responsivity of the PDs. The dark current is reduced due to the use of platinum-gold (Pt/Au) Schottky contacts, characterized by a relatively high Schottky barrier height. The vast improvement of nearly all FOMs, compared to those reported earlier for GaN/Si PDs, is highly encouraging for the development of low-cost, large-area arrays of visible-blind PDs.