Phonon-assisted tunneling in Schottky barriers

Experimental current-voltage characteristics and their temperature dependencies for AlGaAs Schottky barrier structures are shown to be in agreement with the recent theory of phonon-assisted tunneling.     

Electrical properties of metal-GaAs Schottky barriers

Schottky barrier contacts have been fabricated by vacuum evaporation of thin films of six different metals (Mg, In, Al, Au, Bi and Sb) onto chemically cleaned n-type GaAs substrates. Bi and Sb contacts on GaAs have been reported for the first time. The contacts were examined for their C-V and I-V characteristics. The diodes exhibit near ideal characteristics for all the metals with values of the ideality factor n ranging from 1.06 to 1.1. The values of the barrier height obtained from C-V measurements could be brought into agreement with those obtained from I-V measurements only when the ideality factor was also included in the expression of the saturation current. By employing the most recent and reliable values of metal work function φ_M, the dependence of barrier height on φ_M has been investigated and an estimate of the surface state density and the Fermi level at the GaAs surface has been made. The surface state density obtained from this analysis is significantly larger than that reported by previous workers.     

Schottky barriers in carbon nanotube heterojunctions

Electronic properties of heterojunctions between metallic and semiconducting single-wall carbon nanotubes are investigated. Ineffective screening of the long-range Coulomb interaction in one-dimensional nanotube systems drastically modifies the charge transfer phenomena compared to conventional semiconductor heterostructures. The length of depletion region varies over a wide range sensitively depending on the doping strength. The Schottky barrier gives rise to an asymmetry of the I-V characteristics of heterojunctions, in agreement with recent experimental results by Yao et al. and Fuhrer et al. Dynamic charge buildup near the junction results in a steplike growth of the current at reverse bias.     

Polytypism of silicon carbide and Schottky barriers

The results obtained in our previous work [4] are revised taking into account the dependence of the electron affinity on the polytype of silicon carbide SiC. The dependence of the energy level of vacancies in a polytype of silicon carbide on the band gap is determined from the data on the Schottky barrier height and is explained in the framework of a simple two-band model.     

Direct probing of Schottky barriers in Si nanowire Schottky barrier field effect transistors

This work elucidates the role of the Schottky junction in the electronic transport of nanometer-scale transistors. In the example of Schottky barrier silicon nanowire field effect transistors, an electrical scanning probe technique is applied to examine the charge transport effects of a nanometer-scale local top gate during operation. The results prove experimentally that Schottky barriers control the charge carrier transport in these devices. In addition, a proof of concept for a reprogrammable nonvolatile memory device based on band bending at the Schottky barriers will be shown.     

Reverse characteristics of AgGaS Schottky barriers

It is shown that the current-voltage relation of AgGaS surface barriers can be described within the diffusion theory for Schottky barriers, corrected for the image-force lowering of the barrierheight. The barrier lowering is independently determined from photo-response measurements which yield an image-force dielectric constant of 5.0.     

Amorphous and crystalline IrSi Schottky barriers on silicon

The electro-optical properties of the films are studied by measuring the infrared optical absorption and the yield of hole photoemission across the Schottky barrier to the p-Si substrate. The Schottky barrier height of the amorphous a-IrSi to the valence band of Si is 0.17–0.18 eV. The barrier height of the polycrystalline c-IrSi depends on the degree of texturing of the silicide; the Schottky barrier height increases from 0.14 eV to 0.18 eV when the substrate temperature is increased from room temperature to 400 °C during the Ir metal deposition prior to the 500 °C silicidation. The non-linearity of the photoemission yield observed for the amorphous a-IrSi in the Fowler plot is due to an energy-dependent photon absorption of these amorphous films. An evaluation of the scattering events in the metal films shows that the mean free path for inelastic scattering is λ_in=500 nm in the amorphous a-IrSi which is one order of magnitude larger than that in the crystalline c-IrSi. The mean free path for quasi-elastic scattering λ_qe=0.3 nm, of the amorphous a-IrSi is in the order of the interatomic distance, indicating a localization of the electronic states. Received: 14 November 1997/Accepted: 12 January 1998     

Schottky barriers on diamond (1 1 1)

We have measured Schottky barrier heights Ø_B = 1.3 eV for Au and Ø_B = 1.5 eV for Al on (p-type) diamond(1 1 1)?(1 × 1) using photoelectron spectroscopy with synchroton radiation. These barrier heights yield a barrier index of S = 0.2, which is closer to the values for Si and Ge (S ～ 0.1) than to the value S = 0.4 calculated for jellium on an ideal diamond(1 1 1) surface. After reacting Al with the diamond surface by annealing to 800° C, we find that Ø_B decreases by 0.24 to 1.25 eV.     

Origin of Schottky barriers in gold contacts on GaAs110

Gold contacts on n-type GaAs(110) have been investigated using scanning tunneling microscopy and spectroscopy in cross-sectional configuration. In spatially resolved current voltage spectroscopy the Schottky barrier potential is visible. We find signatures of delocalized gap states at the interface decaying into the semiconductor and observe a defect density at the interface below 3 x 10(13) cm(-2). Both findings support that the Fermi level pinning at the Au/GaAs(110) interface is dominated by metal-induced gap states.     

Photoelectric properties of In/n-CuIn5Se8 Schottky barriers

We have grown homogeneous CuIn₅Se₈ crystals with n-type conductivity and determined the activation energy for the donor centers. We created In/n-CuIn₅Se₈ Schottky barriers and obtained the first spectral dependences of the photoconversion quantum efficiency of these structures. From the results of analysis of the photoactive absorption edge of the Schottky barriers, we have interpreted the nature of the interband optical transitions and determined the bandgap for direct and indirect transitions in CuIn₅Se₈ crystals. We have established that it is feasible to use CuIn₅Se₈ in broadband optical photoconverters. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 4, pp. 502–505, July–August, 2006.     

Design and performance of Yb/ZnS/C Schottky barriers

In this work, ZnS thin films are deposited onto glass and transparent ytterbium substrates under vacuum pressure of 10^?5 mbar. The effects of the Yb substrate on the structural, mechanical, optical, dielectric and electrical performance of the ZnS are explored by means of the energy dispersion X-ray analyzer, X-ray diffraction, UV–VIS spectroscopy, current-voltage characteristics and impedance spectroscopy techniques. The techniques allowed determining the lattice parameters, the grain size, the degree of orientation, the microstrain, the dislocation density, the optical and the excitonic gaps, the energy band offsets and the dielectric resonance and dispersion. The (111) oriented planes of glass/ZnS and Yb/ZnS exhibited 2.06% lattice mismatch between Yb and ZnS and degree of orientation values of 63% and 51.6%, respectively. The interfacing of the ZnS with Yb shrunk the energy band gap of ZnS by 0.50 eV. On the other hand, the electrical analysis on the Yb/ZnS/C Schottky device has revealed a rectification ratio of 3.48 × 10⁴ at a biasing voltage of 0.30 V. The barrier height and ideality factor was also determined. Moreover, the impedance spectroscopy analysis have shown that the Yb/ZnS/C device is very attractive for use as varactor devices of wide tunability. The device could also be employed as microwave resonator above 1337 MHz.     

Investigation of the Schottky barriers in aluminum — vitreous semiconductor contacts

In the present paper, results of investigations of the Schottky barriers based on aluminum — chalcogenide vitreous semiconductor contacts are given. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 73–76, October, 2005.     

Photoelectric Properties of Photodetectors Based on Silicon–Platinum Silicide Schottky Barriers with a Highly-Doped Surface Layer

We have calculated the spectral, threshold, and noise characteristics of p-Si–PtSi photodetectors with highly-doped surface layers produced by molecular-beam epitaxy and short-pulse ion implantation by a recoil method.     

Analysis of thermionic emission from electrodeposited Ni–Si Schottky barriers

Ni–Si Schottky barriers are fabricated by electrodeposition using n on n+ Si substrates. I–V, C–V and low temperature I–V measurements are presented. A high-quality Schottky barrier with extremely low reverse leakage current is revealed. The results are shown to fit an inhomogeneous barrier model for thermionic emission over a Schottky barrier proposed by Werner and Guttler [J.H. Werner, H.H. Guttler, Barrier inhomogeneities at Schottky contacts, J. Appl. Phys. 69 (3) (1991) 1522–1533]. A mean value of 0.76 V and a standard deviation of 66 mV is obtained for the Schottky barrier height at room temperature with a linear bias dependence. X-ray diffraction and scanning electron microscopy measurements reveal a polycrystalline Ni film with grains that span from the Ni–Si interface to the top of the Ni layer. The variation in Ni orientation is suggested as a possible source of the spatial distribution of the Schottky barrier height.     

Ultraviolet photoelectron spectroscopy of nano In clusters Schottky barriers on sputtered InP

Plasmon peaks along with Auger P_LVV peak have been observed in the ultraviolet photoelectron spectra (UPSs) of InP after 5 min of sputtering with 0.5 kV Ar⁺ ions. Plasmon and Auger peaks are not observed in UPS of un-sputtered InP surface with native oxides of In and P. Filled electron energy levels are not observed near the Fermi level from 5 min sputtered InP surface due to increase of ionization potential of nano In clusters.     

Mo/GaAs Schottky barriers prepared by d.c. sputtering

Summary Mo/GaAs Schottky barriers have been prepared by d.c. sputtering, for different values of the sputtering voltage. Current-voltage and capacitance-voltage measurements show that these barriers can have very good properties (near one ideality factor, very low inverse saturation current) if suitable preparation conditions are chosen. A detailed study of the current-voltage characteristics as a function of the temperature allows us to analyse the carrier transport mechanisms and to correlate them to the preparation conditions. The experimental results show that the behaviour of the Mo/GaAs Schottky barriers, prepared by d.c. sputtering, can be successfully explained on the basis of the unified defect model proposed for the GaAs schottky barriers.

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Riassunto In questo lavoro vengono presentati risultati concernenti barriere Schottky Mo/GaAs preparate mediante ?sputtering? in continua, per diversi valori delle tensioni di ?sputtering?. Le misure di caratteristiche corrente-tensione e capacità-tensione mostrano che è possibile ottenere barriere con buone caratteristiche elettriche (fattore di idealità prossimo ad uno, corrente di saturazione inversa molto bassa), purché siano scelte le giuste condizioni di deposizione. è stato anche condotto uno studio dettagliato delle ricavare informazioni sul meccanismo di trasporto dei portatori di carica. I risultati sperimentali mostrano che il comportamento di questo tipo di barriere è perfettamente spiegabile nell'ambito del modello unificato dei difetti nelle barriere Schottky nel GaAs.

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Резюме Барьеры Шоттки Mo/GaAs приготовлены с помощью распыления при различных значениях напряЗения распыления. Измерения зависимостей тока от напряЗения и емкости от напряЗения показывают, что зти барьеры могут иметь очень хорощие свойства, если выбираются соответствующие условия приготовления. Подробное исследование вольт-амперных характеристик в зависимости от температуры позволяет проанализировать механизмы переноса заряда и связать их с усломиями приготовления. Зкспериментальые результаты показывают, что поведение барьеров Шоттки Mo/GaAs, приготовленных с помощьюDC распыления, моЗно успешно объяснить на основе единой модели дефектов, предлоЗенной для барьеров Шоттки GaAs.