Determination of the laterally homogeneous barrier height of metal/p-InP Schottky barrier diodes

We have reported a study of a number of metal/p-type InP (Cu, Au, Al, Sn, Pb, Ti, Zn) Schottky barrier diodes (SBDs). Each one diode has been identically prepared on p-InP under vacuum conditions with metal deposition. In Schottky diodes, the current transport occurs by thermionic emission over the Schottky barrier. The current–voltage characteristics of Schottky contacts are described by two fitting parameters such as effective barrier height and the ideality factor. Due to lateral inhomogeneities of the barrier height, both characteristic diode parameters differ from one diode to another. We have determined the lateral homogeneous barrier height of the SBDs from the linear relationship between experimental barrier heights and ideality factors that can be explained by lateral inhomogeneity of the barrier height. Furthermore, the barrier heights of metal–semiconductor contacts have been explained by the continuum of metal-induced gap states (MIGS). It has been seen that the laterally homogeneous barrier heights obtained from the experimental data of the metal/p-type InP Schottky contacts quantitatively confirm the predictions of the combination of the physical MIGS and the chemical electronegativity.     

Determination of the laterally homogeneous barrier height of metal/p-InP Schottky barrier diodes

We have reported a study of a number of metal/p-type InP (Cu, Au, Al, Sn, Pb, Ti, Zn) Schottky barrier diodes (SBDs). Each one diode has been identically prepared on p-InP under vacuum conditions with metal deposition. In Schottky diodes, the current transport occurs by thermionic emission over the Schottky barrier. The current–voltage characteristics of Schottky contacts are described by two fitting parameters such as effective barrier height and the ideality factor. Due to lateral inhomogeneities of the barrier height, both characteristic diode parameters differ from one diode to another. We have determined the lateral homogeneous barrier height of the SBDs from the linear relationship between experimental barrier heights and ideality factors that can be explained by lateral inhomogeneity of the barrier height. Furthermore, the barrier heights of metal–semiconductor contacts have been explained by the continuum of metal-induced gap states (MIGS). It has been seen that the laterally homogeneous barrier heights obtained from the experimental data of the metal/p-type InP Schottky contacts quantitatively confirm the predictions of the combination of the physical MIGS and the chemical electronegativity.     

Quantitative Experimental Analysis of Schottky Barriers and Poole–Frenkel Emission in Carbon Nanotube Devices

In this paper, we investigated carbon nanotube FETs (CNT FETs) utilizing semiconducting single-walled CNTs (SWCNTs). Multiple devices, each of different metal source and drain contacts, were fabricated on a single SWCNT. Over specific temperature regimes, transport properties of the devices were found to be consistent with the Bethe theory of thermionic emission for Schottky contacts, and the Poole–Frenkel emission was dependent on the device position. As was expected, transport from thermionic emission over the barrier was found to be the dominant mechanism. Barriers of 25–41 meV were present, as found by activation energy analysis for temperatures ranging from 20 to 300 K for the devices. A Schottky diode was also fabricated on a separate nanotube using an ohmic contact at the Pd source and a Schottky contact for the Ag drain electrode. Assuming the same physical assumptions for an Si semiconductor device, the results indicate an ideality factor greater than 2, Schottky barrier of $sim$0.37 eV, and image charge lowering of $sim$0.1 eV.      

Photovoltaic characterization of amorphous hydrogenated and chlorinated silicon films

Hydrogenated and chlorinated silicon films were used to deposit Schottky barrier solar cells. Photovoltaic characterization, together with the results of electronic transport measurements, led to the conclusion that the presence of chlorine is detrimental to the properties of this kind of device.     

Gate‐Tunable Graphene–WSe2 Heterojunctions at the Schottky–Mott Limit

Metal–semiconductor interfaces, known as Schottky junctions, have long been hindered by defects and impurities. Such imperfections dominate the electrical characteristics of the junction by pinning the metal Fermi energy. Here, a graphene–WSe₂ p‐type Schottky junction, which exhibits a lack of Fermi level pinning, is studied. The Schottky junction displays near‐ideal diode characteristics with large gate tunability and small leakage currents. Using a gate electrostatically coupled to the WSe₂ channel to tune the Schottky barrier height, the Schottky–Mott limit is probed in a single device. As a special manifestation of the tunable Schottky barrier, a diode with a dynamically controlled ideality factor is demonstrated.     

Carbon nanotube Schottky diode: an atomic perspective

The electron transport properties of semiconducting carbon nanotube (SCNT) Schottky diodes are investigated with atomic models using density functional theory and the non-equilibrium Green's function method. We model the SCNT Schottky diode as a SCNT embedded in the metal electrode, which resembles the experimental set-up. Our study reveals that the rectification behaviour of the diode is mainly due to the asymmetric electron transmission function distribution in the conduction and valence bands and can be improved by changing metal-SCNT contact geometries. The threshold voltage of the diode depends on the electron Schottky barrier height which can be tuned by altering the diameter of the SCNT. Contrary to the traditional perception, the metal-SCNT contact region exhibits better conductivity than the other parts of the diode.     

A SPICE-Compatible New Silicon Nanowire Field-Effect Transistors (SNWFETs) Model

Extraction of carrier mobilities of silicon nanowire FETs (SNWFETs) with Schottky source and drain contacts is performed using a newly developed compact model, which is suitable for efficient circuit simulation. The SNWFET model is based on an equivalent circuit including a Schottky diode model for two metal-semiconductor contacts and a SPICE LEVEL 3 MOSFET model for an intrinsic NW. The Schottky diode model is based on our recently developed Schottky diode model that includes thermionic field emission for reverse bias and thermionic emission mechanism for forward bias. It also includes a new analytical Schottky barrier height model dependent on the gate voltages as well as the drain-source voltages. The results simulated from the SNWFET model reproduce various, previously reported experimental results within 10% errors. The mobilities extracted from our model are compared with the mobility calculated without considering the Schottky contacts.     

Electrical characterization of n/p-type nickel silicide/silicon junctions by Sb segregation

In this paper, n/p-type nickel-silicided Schottky diodes were fabricated by incorporating antimony atoms near the nickel silicide/Si junction interface and the electrical characteristics were studied through measurements and simulations. The effective Schottky barrier height (SBH) for electron, extracted from the thermionic emission model, drastically decreased from 0.68 to less than 0.1 eV while that for hole slightly increased from 0.43 to 0.53 eV. In order to identify the current conduction mechanisms, the experimental current-temperature-voltage characteristics for the n-type diode were fitted based on various models for transport of charge carrier in Schottky diodes. As the result, the large change in effective SBH for electron is ascribed to trap-assisted tunneling rather than barrier height inhomogeneity.     

Graphene-silicon Schottky diodes

We have fabricated graphene-silicon Schottky diodes by depositing mechanically exfoliated graphene on top of silicon substrates. The resulting current-voltage characteristics exhibit rectifying diode behavior with a barrier energy of 0.41 eV on n-type silicon and 0.45 eV on p-type silicon at the room temperature. The I-V characteristics measured at 100, 300, and 400 K indicate that temperature strongly influences the ideality factor of graphene-silicon Schottky diodes. The ideality factor, however, does not depend strongly on the number of graphene layers. The optical transparency of the thin graphene layer allows the underlying silicon substrate to absorb incident laser light and generate a photocurrent. Spatially resolved photocurrent measurements reveal the importance of inhomogeneity and series resistance in the devices.     

Influence of annealing effects on the electrical and microstructural properties of Se Schottky contacts on n-type GaN

The electrical and microstructural properties of Se/n-gallium nitride (GaN) Schottky diode have been investigated by current–voltage (I–V), capacitance–voltage (C–V) and transmission electron microscopy (TEM) measurements as a function of annealing temperature. The Se/n-GaN Schottky contact exhibited an excellent rectification behavior. The barrier height of the as-deposited Se/n-GaN Schottky contact is 0.94 eV (I–V) and 1.55 eV (C–V), respectively. However, the barrier height of Se/n-GaN Schottky diode decreases to 0.90 eV (I–V) and 1.33 eV (C–V) upon annealing at 200 °C. Cheung’s and modified Norde functions are employed to determine the barrier height and series resistance. TEM results reveal that the Se film becomes fully crystallized for the contact annealed at 200 °C compared to the as-deposited contact without the reaction between Se film and GaN substrate. It is observed that the barrier height of Se/n-GaN Schottky diode decreases with increasing annealing temperature. This could be associated with the decrease in series resistance caused by the phase transformation from high resistance amorphous Se to low resistance crystalline Se. Further, the interface states density is found to be increased with the increasing annealing temperature. The Schottky emission mechanism is found to dominate the reverse leakage current in Se/n-GaN Schottky diodes irrespective of annealing temperatures.     

Current–voltage characteristics and inhomogeneous barrier height analysis of Au/poly(o-toluidine)/p-Si/Al heterojunction diode

Thin films of poly(o-toluidine) (POT) with amorphous structure were prepared onto the surface of p-Si single crystal by spin coating technique. The electrical conduction mechanisms and related parameters of the Au/POT/p-Si/Al heterojunction diode were investigated using current–voltage (I–V) characteristics in temperature range 298–378 K. The device showed rectifying behavior. At relatively low forward applied voltages; the current through the junction has been analyzed on the bases of the standard thermionic emission theory. The ideality factor decreases with increasing temperature, whereas the barrier height increases. This behavior could be elucidated in terms of inhomogeneity model of barrier heights. In addition, the values of series resistance, ideality factor and effective barrier height at zero-bias are determined at different temperatures by using Cheung’s functions. At relatively high forward bias voltages, analysis of the double logarithmic I–V characteristics indicates that transport through the device is controlled by a space-charge-limited current process characterized by single trap of distribution in which the related parameters are estimated. Data analysis in reverse direction showed that the current can be described in terms of Poole–Frenkel mechanism at low applied voltage and in terms of Schottky mechanism at higher applied voltage.     

A TaSix barrier for low resistivity and high reliability of contacts to shallow diffusion regions in silicon

It is shown that a thin TaSi_x layer underneath the aluminium-based metallization considerably improves the contacts from the metallization to shallow diffusion regions in silicon. TaSi_x with x < 2 acts as a barrier against aluminium and silicon diffusion at the contacts and thus impedes aluminium spiking as well as silicon precipitates in the contacts. Furthermore the silicon erosion induced by high currents is reduced by one order of magnitude. The contact resistance to n⁺ -Si is decreased by a factor of 3–5. Finally the TaSi_x provides a low barrier Schottky diode on lightly doped n-Si and p-Si.     

Quantum mechanical simulation of hole transport in p-type Si Schottky barrier MOSFETs

A full quantum-mechanical simulation of p-type nanowire Schottky barrier metal oxide silicon field effect transistors (SB-MOSFETs) is performed by solving the three-dimensional Schr?dinger and Poisson's equations self-consistently. The non-equilibrium Green's function (NEGF) approach is adopted to treat hole transport, especially quantum tunneling through SB. In this work, p-type nanowire SB-MOSFETs are simulated based on the 3-band k.p method, using the k.p parameters that were tuned by benchmarking against the tight-binding method with sp3s* orbitals. The device shows a strong dependence on the transport direction, due to the orientation-sensitive tunneling effective mass and the confinement energy. With regard to the subthreshold slope, the [110] and [111] oriented devices with long channel show better performance, but they are more vulnerable to the short channel effects than the [100] oriented device. The threshold voltage also shows a greater variation in the [110] and [111] oriented devices with the decrease of the channel length.     

Characteristics of Schottky barrier silicon nanocluster floating gate flash memory

The silicon nanocluster floating gate memory device based on the Schottky barrier metal-oxide-semiconductor field effect transistor (SB-MOSFET) was proposed. The silicon nanoclusters were formed via the digital gas-feeding low pressure chemical vapor deposition. Erbium silicide process was used to form the Schottky junctions at the source/drain. In addition to the SB-MOSFET operation, the program/erase times of the nonvolatile memory device were determined to be 10 ms and 100 ms under the + 18 and − 18 V gate bias conditions, respectively. Maximum memory window was 5.5 V and the charge retention characteristics were maintained with a memory window of 0.5 V at 10⁶ s.     

Poly(3-hexylthiophene)-zinc oxide rectifying junctions

The rectifying junction formed at the interface of solvent-cast, as-prepared poly(3-hexylthiophene) (P3HT) and conductive ZnO-coated glass was investigated by recording the l-V and C-V characteristics. The data have been discussed in terms of the Schottky thermionic-emission current transport model. The diode “quality factor” determined for these devices was 3.6, and indicated imperfect model fitting. The Schottky barrier was estimated as 0.93 eV. A negative differential resistance regime was observed for P3HT/ZnO devices under reverse-bias high-field conditions. This effect was concluded to be a filament-formation burnout failure process.     

A Pt/Ga/sub 2/O/sub 3/-ZnO/SiC Schottky diode-based hydrocarbon gas sensor

In this paper, a novel metal-reactive insulator-silicon carbide device with a catalytic layer for hydrocarbon gas-sensing is presented. This structure, employed as a Schottky diode, utilizes sol-gel prepared Ga/sub 2/O/sub 3/-ZnO layer as the reactive insulator. The sensor has been exposed to propene gas, which lowers the barrier height of the diode. The responses were stable and repeatable at operating temperatures between 300 and 600/spl deg/C. The response to propene in different ambients was examined. The effect of diode bias has been investigated by analyzing the sensors response to various propene concentrations when held at constant currents of 2 and 8 mA.     

Electrical properties of Schottky diode Pt/SiC and Pt/porous SiC performed on highly resistif p-type 6H-SiC

We investigated the electrical characteristics of two different Schottky diode as Pt/SiC and Pt/porous SiC, elaborated on highly resistif hot-pressed p-type 6H-SiC supplied by Goodfellow. The Schottky diode was characterized in air ambient and in vacuum, this latter could be used for exhaust gas monitoring as gas sensors for different gas (O₂, H₂, CO, CO₂ and hydrocarbure). The result shows an ideality factor in range 1.1-1.5 with a barrier height varying between 0.780 and 0.950 eV function of the ambient characterization. The result indicated clearly the dependence of electrical parameters on the surface whose Schottky contact was realized (Pt) and on the ambient where the electrical tests were performed.     

A comparative study of position-sensitive detectors based on Schottky barrier crystalline and amorphous silicon structures

The response and properties of thin film position-sensitive detectors (PSDs) fabricated from novel hydrogenated amorphous silicon (a-Si : H) Schottky barrier (SB) structures are compared in this work with conventional crystalline layered devices. The sputtered a-Si : H detectors were configured as SB-intrinsic-n-type (SB-i-n) devices and exhibited properties similar to doped a-Si : H p-i-n diodes produced by conventional plasma-enhanced vapor deposition processes. A figure of merit is the correlation coefficient (r) which measures the linearity of the device output and which has a maximum value of 1. Based on this, the a-Si : H structures gave very promising results (r=0.983 to 0.997), while the overall best results were obtained with crystalline silicon (c-Si) devices, with Pt/c-Si and Au-Zn/c-Si devices having r~1 for a range of measurements. The maximum detectable position range, or spatial resolution, of optical sensors is another figure of merit and in this work this parameter for the crystalline devices was measured to be less than 10 µm while for the a-Si devices it was less than 50µm. A comparison of device response was made using a green diode laser (532 nm) and a red gas laser (633 nm) and a focused white light source.     

结构为Pt/SiNWs/n-Si/Al肖特基二极管的电子特性(英文)

采用湿化学刻蚀法直接在n-Si衬底上制备了硅纳米线(Si NWs),用无电镀法在制备好的硅纳米线上修饰Pt纳米粒子作为上电极以形成结构为Pt/Si NWs/n-Si/Al的肖特基二极管。研究了无电镀参数(如氯铂酸钾K2PtCl6浓度,无电镀时间)对结构为Pt/Si NWs/n-Si/Al的肖特基二极管电流-电压的影响。从所得的电流-电压特性曲线中提取了肖特基二极管的三个特征参数(理想因子、势垒高度以及串联电阻),并分析了这三个特征参数与无电镀参数的关系,从而确定了一个制备结构为Pt/Si NWs/n-Si/Al肖特基二极管的理想条件。研究还发现所制备的肖特基二极管理想因子大于1,势垒高度～0.67eV,与金属铂(Pt)的功函数无关,这些特性可以用巴丁模型来解释。     

Superposed forward current-voltage characteristics in TbMnO3/n-Si and TbMnO3/p-Si heterostructures

TbMnO₃/n-Si (n-N) and TbMnO₃/p-Si (p-n) heterojunctions were fabricated under identical conditions. Good rectifying characteristics were found with almost the same forward current-voltage behavior in a temperature range from 150 to 300 K. Such intriguing superposed rectifying behaviours at the interfaces between TbMnO₃ and Si of two different doped types can be explained by a similar Schottky barrier diode behavior with its current-voltage dependence generally dominated by only one type of carrier. This work will favor both electronic transport analysis and future device applications.