Characteristics Of Schottky Barrier Diodes Research Articles

First-principles investigations and MOCVD growth of Si-doped β-Ga2O3 thin films on sapphire substrates for enhancing Schottky barrier diode characteristics

In the realm of high-power electronics, the potential of gallium oxide (β-Ga2O3) as a front-runner material has garnered significant attention due to its wide bandgap and the capacity to withstand high critical electric fields. To push the boundaries of performance for β-Ga2O3 devices, a meticulous exploration into the effects of silicon (Si) doping on β-Ga2O3 films was carried out using the metalorganic chemical vapor deposition (MOCVD) technique with various tetraethoxysilane (TEOS) flow rates (0–30 sccm). The Si-doped β-Ga2O3 films were systematically studied and characterized using XRD, SEM, and XPS techniques. XRD patterns demonstrated the preservation of the β-Ga2O3 monoclinic structure in the Si-doped β-Ga2O3 films, without any evidence of secondary phases. In addition to this, first-principles calculations were performed to explore the incorporation of Si atoms in Ga2O3 supercells, which revealed the preference of Si atoms to occupy substitutional Ga tetrahedral sites within the Ga2O3 lattice. Through the utilization of Si-doped β-Ga2O3 films, a unique design of donut-shaped Schottky barrier diode (SBD) was successfully engineered. Remarkably, the Si-doped β-Ga2O3 SBD (employed with 20 sccm TEOS flow rate) exhibited the breakdown voltage (Vbr) of 497 V and Baliga's Figure of Merit (BFOM) value of 1.16 kW/cm2, which is five-order higher BFOM compared to undoped β-Ga2O3 SBD. This substantial improvement in BFOM underscores the significant potential of Si-doped β-Ga2O3 films for high-power electronics, opening avenues for enhanced device efficiency and capabilities.

Voltage and Current Characteristics of Schottky Barrier Diodes and Rectifier Diodes Exposed to Standard Lightning Impulse Voltage

Lightning surges are one of the major reasons of bypass diode (BPD) failure in photovoltaic modules. In this study, standard lightning impulse voltages (SLIVs) were directly applied to Schottky barrier diodes (SKB diodes) and rectifier diodes (PNJ diodes) with different electrical specifications. The critical voltages Vc of SLIV at which the diodes were damaged and the temporal variations of diode current (iD) and voltage (vD) were measured. It was found the iD‐vD characteristics can be categorized into a total of eight patterns: four patterns for the forward SLIV application and the four for the reverse SLIV application, regardless of diode types. The measured results imply that the irreversible voltage dip that occurs before the termination of the reverse breakdown contributes significantly to diode damage in the both forward and reverse SLIV applications. SKB diodes exposed to the reverse SLIV are easily damaged at the lowest magnitude of SLIV among all combinations of diode types and SLIV directions. Once a diode has been damaged due to the first SLIV application, the second application of SLIV to the same diode causes remarkable change in the iD‐vD characteristic even if the magnitude of the second SLIV is smaller than Vc. © 2024 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Characterization of the electrical properties of MPS schottky structures incorporating Fe doped polyvinyl chloride (PVC)

This paper explores the effects of the organic interfacial layer on the electrophysical characteristics of Schottky barrier diodes (SBDs). Three types of SBDs were fabricated: Au-Si (referred to as MS), Au/PVC/Si (referred to as MPS1), and Au-/PVC:Fe/Si (referred to as MPS2). Fe nanopowders were subjected to analysis using XRD, SEM, and EDX techniques to investigate their structural and optical characteristics. To investigate the conduction mechanisms of these diodes, I-V characteristics were examined using thermionic-emission (TE), Cheung, and Norde functions. The surface-state density (N ss ) distribution of energy was determined by analyzing the current–voltage (IF-VF) curve under forward bias conditions. This analysis considered the voltage-dependent barrier height (BH) and ideality factor (n(V)). The results demonstrated that the polymeric interlayer without Fe nanoparticles reduced N ss by a factor of 7, while the presence of Fe nanoparticles led to a two-order magnitude decrease, resulting in improved efficiency in comparison with MS structures. The obtained results indicated that including a polymeric layer in MPS structure enhanced their electrophysical features compared to MS diodes, and significantly increased rectification by 15–45 times. In summary, the existence of an organic interfacial layer significantly altered the conduction mechanisms and electrophysical characteristics of MPS diodes. It was found that the addition of Fe nanoparticles in the interlayer resulted in substantial improvements in N ss , efficiency, rectification, and conduction characteristics compared to MS diodes.

Breakdown Characteristics of Schottky Barrier Diodes Used as Bypass Diodes in Photovoltaic Modules under Lightning Surges

Damage to photovoltaic power-generation systems by lightning causes the failure of bypass diodes (BPDs) in solar cell modules. Bypass diodes damaged by lightning experience high-resistance open- or short-circuit failures. When a bypass diode experiences short-circuit failure due to indirect lightning, the damage may not be immediately visible. When solar radiation is subsequently received, the current circulating in the closed circuit formed by the cell string and short-circuited bypass diode flows, resulting in overheating and burnout of the short-circuited bypass diode. The authors’ research group previously reported that when a bypass diode fails within a range of approximately 10−1 Ω to 10 Ω, the heat generated by the failed bypass diode is high, posing the risk of burnout. However, the detailed failure characteristics of the bypass diode that fail because of indirect lightning surges are not clear. In this study, we performed indirect lightning fracture tests and clarified the dielectric breakdown characteristics of Schottky barrier diodes (SBDs) contained in the bypass diodes of photovoltaic solar cell modules, which are subjected to indirect lightning surges. Furthermore, we attempted to determine the conditions of indirect lightning that resulted in a higher risk of heat and ignition. As a result, short-circuit failures occurred in all the Schottky barrier diodes that were destroyed in the forward or reverse direction because of the indirect lightning surges. Moreover, the fault resistance decreased as the indirect lightning surge charge increased. These results indicate that the risks of heat generation and burnout increase when the Schottky barrier diode fails with a relatively low electric charge from an indirect lightning surge. In addition, we observed that for a forward breakdown of the Schottky barrier diode, the range of the indirect lightning surge that results in a fault condition with a higher risk of heat generation and burnout is wider than that for a reverse breakdown.

A compact model based on the Lambert function for AlGaN/GaN Schottky barrier gated-edge termination

A compact model based on the Lambert function is used to describe I-V-T characteristics of Schottky Barrier Diodes (SBDs) with gated-edge termination (GET) with either SiN or SiO/AlO as GET dielectric. Electrical parameters obtained from this model enable Schottky barrier height (SBH) assessment. It will be shown that fluctuations are about 17% in both cases. Similar interface state density (from ideality factor) is obtained which is consistent with previous work and validates this approach as an interesting method to model these GET-SBDs.

Modeling of Stacking Faults in 4H-SiC n-Type Epilayer for TCAD Simulation

Current–voltage characteristics of an n-type 4H-silicon carbide (SiC) epilayer containing a stacking fault (SF) were analyzed using a technology computer-aided design (TCAD) simulation. In the simulation, the SF was modeled by a quantum well (QW) formed in the conduction band, which traps electrons and induces a potential barrier. The simulation analysis clarified that the electron conductance in the n-type epilayer containing a SF was dominantly determined by the potential barrier height. Based on this insight and the experimental results obtained from our previous study, the energetic depth and width of the QW in the conduction band were deduced for four types of SFs. The temperature dependence of the experimental current–voltage characteristics of Schottky barrier diodes (SBDs), containing the SF, was effectively reproduced by adopting the deduced QW depth and width, proving the feasibility of the proposed simulation model quantitatively predicting the impacts of SFs on SiC unipolar device performances.

Large-area vertical-geometry Pt/(010) β-Ga2O3 Schottky barrier diodes and their temperature-dependent electrical properties

Herein, vertical-geometry Pt/(010) β-Ga2O3 Schottky barrier diodes (SBDs) with various large areas (2.25 × 10−2, 4 × 10−2 to 6.25 × 10−2 cm2) were fabricated on (010) orientation β-Ga2O3 substrates. The electrical properties of different area diodes and the uniformity of diodes with the same area were analyzed. The rectifying ratio of all diodes was determined to be larger than 108 at the bias of ±2 V. The current-voltage (I–V) characteristics of SBD with an area of 2.25 × 10−2 cm2 were investigated in detail from 300 to 450 K. The parameters of the diodes show a strong dependence on temperature, including ideality factor (n), on-resistance (Ron), turn-on voltage (Von), and the Schottky barrier (Φb). The results indicate that a dominant inhomogeneous Schottky barrier exists at the Pt/β-Ga2O3 interface. Such large-area devices exhibit that the value of n is close to 1 and the value of Φb was 1.09 eV at zero bias. In addition, the Von remains low and the stability remains good even after the tests at 450 K. These results indicate that we have successfully fabricated large-area SBDs with excellent performances. This work may contribute to further understanding of the performance of β-Ga2O3 diodes in large areas and harsh environments.

Fabrication of Low-Threshold Discreet Schottky Barrier Diode Using Natural Pyrite Crystal

A low-threshold schottky barrier diode using natural pyrite has successfully been fabricated for the first time. The schottky and ohmic electrodes were successfully mounted and molded onto natural FeS2(pyrite) crystals. The I-V characteristics of the devices were measured, and the typical Schottky barrier diode characteristics were confirmed. The barrier height estimated by fitting was shown to be as low as 0.60 eV, indicating that the device has low-threshold characteristics.

Effect of surface irregularities on diamond Schottky barrier diode with threading dislocations

Pyramidal and flat-type hillocks, both known for having a threading dislocation in the center, are utilized to examine the effect of surface irregularities on the characteristics of Schottky barrier diodes (SBDs). By performing RAMAN mapping on both hillocks, crystalline imperfections in three dimensions with clear strain are observed. Surface scanning images obtained via atomic force microscopy show an extremely large surface protrusion with a maximum height of approximately 15 nm in the pyramidal hillock. Owing to crystalline imperfections in the threading dislocation region, the SBDs fabricated on the dislocations exhibit inferior forward characteristics. However, high reverse leakage currents are only observed in dislocations on pyramidal hillocks with surface protrusions, whereas low reverse currents are observed in the flat hillock region without surface irregularities. The phenomenon above is consistent with the characteristics of wide bandgap semiconductors such as silicon carbide.

Comparison of thermal stabilities of p+-Si/p-diamond heterojunction and Al/p-diamond Schottky barrier diodes

Abstract We evaluate the current–voltage (I–V) and temperature-dependent I–V characteristics of p+-Si/p-diamond heterojunction diodes (HDs) fabricated using surface-activated bonding and compare their characteristics with those of Al/p-diamond Schottky barrier diodes (SBDs) fabricated on the same diamond substrate. The ideality factor, reverse-bias current, and on/off ratio of HDs are improved by annealing them at temperatures up to 873 K, which is in good contrast to the characteristics of SBDs. The barrier height at Si/diamond bonding interfaces is decreased by annealing. The difference in response to annealing between HDs and SBDs implies that the density of interface states formed during the surface activation process is decreased by annealing HDs. The characteristics of HDs are degraded by annealing them at 1073 K, which is assumed to be due to the formation of intermediate layers or the occurrence of local strain at Si/diamond bonding interfaces.

Low etching damage surface obtained by a mixed etching method and the influence of surface states on the C–V characteristics of AlGaN/GaN Schottky barrier diodes

A mixed etching method including ICP dry etching and digital etching (plasma oxidation and wet etching) to remove the p-GaN capping layer was investigated. The results indicated that mixed etching can effectively modify the surface damage induced by dry etching and get a smoother surface. Further research revealed that the existence of nitrogen-vacancy-related states (NVRS) in the devices, which was served as discharging centers, played a key role in the discharging effect of the C–V characteristics of Schottky barrier diodes (SBDs). Based on the discharging effect of NVRS, a charge-discharge C–V model was constructed, and demonstrated validity in cases of inadequately-etching of p-GaN and over-etching of AlGaN. This work demonstrates the discharging effect can be weakened by a retained p-GaN thin layer above the AlGaN barrier layer.

Schottky Diode with Asymmetric Metal Contacts on WS2

AbstractDiode characteristics of transition metal dichalcogenides are studied extensively owing to their electrical and optical properties. In particular, the Schottky barrier diode (SBD) structure has advantages, such as its small leakage current and power consumption, over conventional p–n diodes. This study develops an SBD system using n‐type tungsten disulfide (WS2). By depositing a low work function In (ΦIn = 4.1 eV) and high work function Au (ΦAu = 5.1 eV) on n‐type WS2, the diode characteristics are demonstrated to be close to an ideal diode. The In–Au contacts are measured, and SBD characteristics are confirmed with a 1.02 ideality factor at a zero back‐gate voltage at room temperature and a rectification ratio up to 5 × 102, even at a low temperature (77 K), indicating almost ideal diode properties. In addition, the In electrodes exhibited improved electrical properties, with a high on/off ratio of 107, mobility that is 100 times higher, and Schottky barrier height that is 20 times lower than that of Au electrodes.

Defect-insensitive current–voltage characteristics of Schottky barrier diode formed on heteroepitaxial α-Ga2O3 grown by mist chemical vapor deposition

An n-type α-Ga2O3 layer was grown by mist chemical vapor deposition on a sapphire substrate, and a Ti/α-Ga2O3 Schottky barrier diode was fabricated. Although the α-Ga2O3 layer has a high threading dislocation density (larger than 109 cm−2), the ideality factor of 1.03 was obtained from the forward current–voltage characteristic in the range of 298 K–423 K, indicating the clear thermionic emission transport. The reverse current–voltage characteristic was also investigated, and the leakage current showed good agreement with the theoretical calculation based on the thermionic field emission model without any fitting parameter in the temperature range of 298 K–423 K.

Influence of threading dislocations on diamond Schottky barrier diode characteristics

Influence of dislocations on diamond Schottky barrier diode characteristics of vertical structure p- layer/p+ substrate is studied. Devices are intentionally fabricated at locations corresponding to specific dislocations, stacking faults and growth sector boundaries observed using X-ray topography (XRT) prior to device fabrication. Devices fabricated on [001] threading dislocation area, and threading dislocation with stacking fault (SF) areas showed very large leakage current compared with devices without dislocations. Dislocation vectors of four devices having threading dislocations with SFs, are analyzed using XRT images and compared with current to voltage (I–V) characteristics. The number of threading dislocations and their types vary significantly, and there is not much difference in the I–V characteristics. Thus, threading dislocations are fatal to the device characteristics regardless of their dislocation directions, types, and number counts.

Synergistic enhancement in the microelectronic properties of poly-(dioctylfluorene) based Schottky devices by CdSe quantum dots

This paper reports the potential application of cadmium selenide (CdSe) quantum dots (QDs) in improving the microelectronic characteristics of Schottky barrier diode (SBD) prepared from a semiconducting material poly-(9,9-dioctylfluorene) (F8). Two SBDs, Ag/F8/P3HT/ITO and Ag/F8-CdSe QDs/P3HT/ITO, are fabricated by spin coating a 10 wt% solution of F8 in chloroform and 10:1 wt% solution of F8:CdSe QDs, respectively, on a pre-deposited poly(3-hexylthiophene) (P3HT) on indium tin oxide (ITO) substrate. To study the electronic properties of the fabricated devices, current-voltage (I–V) measurements are carried out at 25 °C in dark conditions. The I–V curves of Ag/F8/P3HT/ITO and Ag/F8-CdSe QDs/P3HT/ITO SBDs demonstrate asymmetrical behavior with forward bias current rectification ratio (RR) of 7.42 ± 0.02 and 142 ± 0.02, respectively, at ± 3.5 V which confirm the formation of depletion region. Other key parameters which govern microelectronic properties of the fabricated devices such as charge carrier mobility (µ), barrier height (ϕb), series resistance (Rs) and quality factor (n) are extracted from their corresponding I–V characteristics. Norde’s and Cheung functions are also applied to characterize the devices to study consistency in various parameters. Significant improvement is found in the values of Rs, n, and RR by 3, 1.7, and 19 times, respectively, for Ag/F8-CdSe QDs/P3HT/ITO SBD as compared to Ag/F8/P3HT/ITO. This enhancement is due to the incorporation of CdSe QDs having 3-dimensional quantum confinement and large surface-to-volume area. Poole-Frenkle and Richardson-Schottky conduction mechanisms are also discussed for both of the devices. Morphology, optical bandgap (1.88 ± 0.5 eV) and photoluminescence (PL) spectrum of CdSe QDs with a peak intensity at 556 nm are also reported and discussed.

Fabrication and characterization of Au/n-type InP Schottky barrier diode with monolayer graphene interlayer

Au/graphene/n-InP Schottky barrier diode (SBD) was fabricated by the use of spray pyrolysis technique with a monolayer graphene interlayer, and the temperature dependent characteristics was performed in a wide temperature range from 60 to 300 K with steps. The Au/GR/n-InP SBD exhibited excellent rectifying behavior however barrier height (Φb0) of the device increased with increasing temperature while ideality factor (n) and series resistance (Rs) decreased. The strong temperature dependency of SBH and the deviation from theoretical value of Richardson constant clarified by considering a Gaussian distribution model of the SBH which was caused by the BH inhomogeneities. The mean BH of 0.94 and 0.59 eV was estimated with the standard deviation of 0.011 and 0.004 eV attributed to the presence of a double GD of SBD. The modified Richardson plots gave mean BH value of 0.98 and 0.70 eV and the Richardson constant values of 8.10, 13,38 A K−2 cm−2 was very close to its theoretical value of 9.4 A K−2 cm−2. These results yields that carrier transport mechanism of Au/GR/n-InP SBD can be clarified by Thermionic-emission-diffusion (TED) mechanism with a double Gaussian distribution of the SBHs. In addition, the I–V characteristics of SBD under dark and light ambiance indicates that Au/graphene/n-InP is strongly dependent on the light effect. Thus, we can conclude that graphene/n-InP device is a potential candidate for photovoltaic systems. Moreover, the UV–vis spectroscopy of the graphene film exhibit a strong absorption as A = 9.45% compared to the literature, that is, Au/GR/n-InP SBD grown by spray pyrolysis has excellent optical properties for optoelectronic applications.

Thermally annealed gamma irradiated Ni/4H-SiC Schottky barrier diode characteristics

Thermal annealing effects on gamma irradiated Ni/4H-SiC Schottky barrier diode (SBD) characteristics are analyzed over a wide range of temperatures (400–1100 °C). The annealing induced variations in the concentration of deep level traps in the SBDs are identified by thermally stimulated capacitance (TSCAP). A little decrease in the trap density at EC – 0.63 eV and EC – 1.13 eV is observed up to the annealing temperature of 600 °C. Whereas, a gamma induced trap at EC – 0.89 eV disappeared after annealing at 500 °C, revealing that its concentration (< 1013 cm−3) is reduced below the detection limit of the TSCAP technique. The electrical characteristics of irradiated SBDs are considerably changed at each annealing temperature. To understand the anomalous variations in the post-annealing characteristics, the interface state density distribution in the annealed SBDs is extracted. The electrical properties are improved at 400 °C due to the reduction in the interface trap density. However, from 500 °C, the electrical parameters are found to degrade with the annealing temperature because of the increase in the interface trap density. From the results, it is noted that the rectifying nature of the SBDs vanishes at or above 800 °C.

Laser-induced interfacial state changes enable tuning of the Schottky-barrier height in SiC

We used a 193-nm ArF excimer laser to produce a surface functional layer with a tunable Schottky barrier height (SBH) on the n-type 4H-SiC surface. The SBHs of the laser-modified layer/SiC contact ranged from 0.38 ± 0.05 to 1.82 ± 0.1 eV. We evaluated the I-V characteristics of Schottky barrier diodes (SBDs) and investigated their corresponding nanoscale current transport characteristics across the laser-modified layer/4H-SiC interface. We attributed changes of the interfacial transport properties between Au and SiC to the laser-induced formation of SiOx/Si compounds with oxygen vacancies in the nitrogen-doped (N-doped) defective graphitic structure. Density functional theory calculations suggested that defect oxide in the SiOx/Si decreased the Schottky barrier width and increased the direct electron tunneling current. Furthermore, the Fermi level of the laser-induced N-doped defective graphitic structure shifted towards the conduction band compared with that of pristine graphene, which was also beneficial for reducing the SBH. This study provides a novel understanding of the interfacial interactions of a laser-modified layer on SiC through nanoscale electrical analysis. These findings will be useful for further investigations of SiC-based nano-photoelectric devices.

Device characteristics of Schottky barrier diodes using In-Ga-Zn-O semiconductor thin films with different atomic ratios

Abstract Oxide semiconductor Schottky barrier diodes (SBDs) were fabricated by using amorphous In-Ga-Zn-O (IGZO) semiconducting thin films with different atomic ratios. Higher rectification ratios and Schottky barrier heights (SBHs) were obtained when the oxygen partial pressure was high during the sputtering deposition of the IGZO films. The increase in Ga composition effectively enhanced the device characteristics, including the rectification ratio and the SBH of the SBDs. These properties were closely related to the control of oxygen vacancy concentration within the IGZO and the resulting conduction behaviors owing to Fermi-level pinning and tunneling current through the Schottky barrier. The fabricated SBD using IGZO with a higher Ga composition (In:Ga:Zn = 1.0:0.8:0.3) exhibited a rectification ratio of 8.3 × 106 and an SBH of 0.79 eV.

Significant improvement in the electrical characteristics of Schottky barrier diodes on molecularly modified Gallium Nitride surfaces

III-Nitride semiconductors face the issue of localized surface states, which causes fermi level pinning and large leakage current at the metal semiconductor interface, thereby degrading the device performance. In this work, we have demonstrated the use of a Self-Assembled Monolayer (SAM) of organic molecules to improve the electrical characteristics of Schottky barrier diodes (SBDs) on n-type Gallium Nitride (n-GaN) epitaxial films. The electrical characteristics of diodes were improved by adsorption of SAM of hydroxyl-phenyl metallated porphyrin organic molecules (Zn-TPPOH) onto the surface of n-GaN. SAM-semiconductor bonding via native oxide on the n-GaN surface was confirmed using X-ray photoelectron spectroscopy measurements. Surface morphology and surface electronic properties were characterized using atomic force microscopy and Kelvin probe force microscopy. Current-voltage characteristics of different metal (Cu, Ni) SBDs on bare n-GaN were compared with those of Cu/Zn-TPPOH/n-GaN and Ni/Zn-TPPOH/n-GaN SBDs. It was found that due to the molecular monolayer, the surface potential of n-GaN was decreased by ∼350 mV. This caused an increase in the Schottky barrier height of Cu and Ni SBDs from 1.13 eV to 1.38 eV and 1.07 eV to 1.22 eV, respectively. In addition to this, the reverse bias leakage current was reduced by 3–4 orders of magnitude for both Cu and Ni SBDs. Such a significant improvement in the electrical performance of the diodes can be very useful for better device functioning.