Showing papers on "Schottky diode published in 1995"

Properties of Silicon Carbide

Abstract: Basic physical properties optical and paramagnetic properties carrier properties and band structure energy levels surface structure, metallization and oxidation etching diffusion of impurities and ion implantation bulk and epitaxial growth contacts and junctions Schottky diodes, transistors and optoelectronic devices.

High performance of high-voltage 4H-SiC Schottky barrier diodes

Abstract: High performance of high-voltage rectifiers could be realized utilizing 4H-SiC Schottky barrier diodes. A typical specific on-resistance (R/sub on/) of these devices was 1.4/spl times/10/sup 3/ /spl Omega/ cm/sup 3/ at 24/spl deg/C (room temperature) with breakdown voltages as high as 800 V. These devices based on 4H-SiC had R/sub on/'s lower than 6H-SiC based high-power rectifiers with the same breakdown voltage. As for Schottky contact metals, Au, Ni, and Ti were employed in this study. The barrier heights of these metals for 4H-SiC were determined by the analysis of current-voltage characteristics, and the reduction of power loss could be achieved by controlling the barrier heights.

Current-voltage characteristics and barrier parameters of Pd2Si/p-Si(111) Schottky diodes in a wide temperature range

Abstract: Current-voltage characteristics of Pd2Si/p-Si(111) Schottky barrier diodes studied over a wide temperature range (60-201 K) are shown to follow a thermionic emission-diffusion mechanism under both the forward and the reverse bias conditions. The barrier parameters as evaluated from the forward I-V data reveal a decrease of zero-bias barrier height ( phi b0) but an increase of ideality factor ( eta ) and series resistance (Rs) with decrease in temperature. Moreover, the changes in phi b0, eta and Rs become quite significant below ~100 K. An In(Is/T2) versus 1/T plot is found to fit well with two straight lines in different temperatures regimes giving an activation energy of 0.33 eV (201-107 K) and 0.24 eV (below 107 K) and an effective Richardson constant of 33 A cm-2 K-2. However, the activation energy of 0.33 eV corresponds to the zero-bias barrier height at absolute zero. An In(Isf/T2) versus 1/ eta T plot is suggested to obtain the flat-band barrier height and the effective Richardson constant; the corresponding values obtained are 0.401 eV and 32.2 A cm-2 K-2 respectively. It is shown that the `T0 effect` cannot account for the apparent increase in ideality factor and decrease of barrier height at low temperatures. Finally, the decrease of barrier height with voltage under the reverse bias condition is attributed mainly to interfacial layer effects with a small contribution due to image force lowering.

Study of schottky barriers on n-type gan grown by low-pressure metalorganic chemical-vapor-deposition

Abstract: Schottky barriers on n‐type GaN films grown by low‐pressure metalorganic chemical vapor deposition are characterized and derived. A thin Pt or a Pd layer is deposited by electron‐gun evaporation to form Schottky contacts in a vacuum below 1×10−6 Torr. The Schottky barrier heights of Pt on the n‐GaN film are determined to be 1.04 and 1.03 eV by current–voltage (C–V) and current density–temperature (J–T) measurements, respectively. Also based on C–V and J–T measurements, the measured barrier height of Pd on n‐GaN is 0.94 and 0.91 eV, respectively. Schottky characteristics of Pt and Pd observed in the experiment are compared with those of Au and Ti in previous reports.

Electrical impedance measurements of polymer light-emitting diodes

Abstract: We report electrical impedance measurements of polymer light‐emitting diodes employing the soluble, conjugated polymer poly[2‐methoxy, 5‐(2’‐ethyl‐hexyloxy)‐1,4‐phenylene vinylene] (MEH‐PPV) as the light‐emitting layer. The diode structures were metal‐polymer‐metal structures utilizing thin gold as the transparent, positive contact, and calcium as the negative contact. The devices were fabricated using undoped, polymer active layers ∼40 nm thick. The polymer light‐emitting diodes are accurately modeled as a resistor and capacitor in parallel for frequencies from 100 Hz to 1 MHz and for bias conditions from reverse bias to forward current densities of 0.1 A/cm2. The diode capacitance as a function of bias voltage is qualitatively different from conventional Schottky or p‐n junction diodes; in reverse bias, the polymer layer is fully depleted and the capacitance is independent of bias; at small forward bias, traps are charged near the metallic contacts and the capacitance increases; under large forward bias, with significant electron and hole injection, the traps are neutralized and the capacitance decreases. From the magnitude of the initial increase in capacitance with forward bias the trap density is estimated to be only a few times 1016 cm−3.

Evaluation of synchronous-rectification efficiency improvement limits in forward converters

Abstract: Design trade-offs for different implementations of the forward power converter with synchronous rectifiers are presented, and effects of the synchronous rectifier driving method on the conversion efficiency are evaluated. Specifically, the merits and limitations of the RCD-clamp and active-clamp reset approaches for a power converter with self-driven synchronous rectifiers are discussed. Estimates of the upper limits of the efficiency improvements of the discussed synchronous rectification approaches relative to the Schottky diode implementation are derived. Finally, experimental comparisons of efficiencies for an offline, 3.3 V/20 A forward power converter power stage are presented and compared with the theoretically estimated ones. >

Hot insertion power arrangement

Abstract: A plug-in module receives both primary and alternate power via mating connectors on the module and on the backplane. Multilevel connectors are used so that a module being inserted first receives alternate power and ground before primary power and signal connections are made. The initial connect to the alternate power supply directs the transient current to the alternate power supply through an isolating PN junction diode having a forward bias voltage drop of about 0.8 volts. When the module is fully inserted, the module is connected to both the primary and alternate power. Within each module the associated electrical load is now connected directly to the primary power bus. To prevent transient currents produced by the hot insertion of other plug-in modules from affecting the voltage level on the power bus, the primary voltage supply is connected to the primary power bus via a Schottky diode having a forward bias voltage of approximately 0.4 volts. Due to the lower voltage drop by the Schottky diode, the isolating PN junction diode is no longer forward biased when the primary power is connected to the module. The alternate power bus will thus supply power to the module only during the short time from initial insertion into the backplane until the module is fully inserted.

High voltage 4H-SiC Schottky barrier diodes

Abstract: Characteristics of 4H-SiC Schottky barrier diodes with breakdown voltages up to 1000 V are reported for the first time. The diodes showed excellent forward I-V characteristics, with a forward voltage drop of 1.06 V at an on-state current density of 100 A/cm/sup 2/. The specific on-resistance for these diodes was found to be low (2/spl times/10/sup -3/ /spl Omega/-cm/sup 2/ at room temperature) and showed a T/sup 1.6/ variation with temperature. Titanium Schottky barrier height was determined to be 0.99 eV independent of the temperature. The breakdown voltage of the diodes was found to decrease with temperature.

Electrical Properties of Paraelectric(Pb0.72La0.28)TiO3 Thin Films with High Linear Dielectric Permittivity: Schottky and Ohmic Contacts.

Abstract: Linear, paraelectric (Pb072La028)TiO3 or PLT(28) thin films with a bandgap>3 eV were deposited on Pt/Ti/SiO2/Si substrates by the sol-gel technique Specific top-contact metals from two distinct groups (ie, non-noble or M T and noble or M N; the former being oxidizable transition metals) were selected to understand the electrical nature of the interfaces in terms of electrode dependent energy band diagrams and equivalent circuit models Using a high sensitivity high-pass filter circuit to evaluate the charging and discharging behavior coupled with results of the thickness and voltage dependence of capacitance, it was determined that M T ( Ni,Cr,Ti) and M N ( Pt,Au,Ag) metals form Ohmic and Schottky contacts, respectively Supported by thermochemical data and calculations, the ohmic M T- PLT interfaces are envisioned to be of the form: M T-M T Ox-n+ PLT-n PLT In contrast, the M N- PLT interfaces may be characterized by a metal work function independent Schottky diode; the surface Fermi level being pinned at the mid-gap For example, a Schottky barrier height of 183 eV and a built-in voltage of 13 eV at the Pt-PLT interface were estimated From low field capacitance measurements, the ratio of interfacial to bulk resistance, R i/R b, was estimated to be 23

Trench MOS Barrier Schottky (TMBS) rectifier: A Schottky rectifier with higher than parallel plane breakdown voltage

Abstract: A new rectifier structure, called Trench MOS Barrier Schottky (TMBS) rectifier, is proposed and demonstrated by modeling and fabrication to have excellent characteristics. Two-dimensional numerical simulations have demonstrated coupling between the charge in the N − drift region and the metal on the trench sidewalls resulting in an improved electric field distribution. For epitaxial layer doping of 1 × 10 17 cm −3 , simulations show that break-down voltages of three times the plane parallel breakdown can be achieved with low leakage current. The measured on-state voltage drops for the devices fabricated using 0.5 μm technology at 60 and 300 A/cm 2 were 0.2 and 0.28 V, respectively. Due to smaller drift region resistances, TMBS rectifiers can be operated at large current densities (∼ 300 A/cm 2 ) resulting in small evice sizes.

Nondegenerate continuum model for polymer light‐emitting diodes

Abstract: We present a device model to describe polymer light‐emitting diodes (PLEDs) under bias conditions for which strong electrical injection does not occur (i.e., reverse, zero, and weak forward bias). The model is useful to interpret: capacitance–voltage measurements, which probe the charged trap density in the PLEDs; electroabsorption measurements on PLEDs, which probe the built‐in electric field in the device; and internal photoemission measurements, which probe the effective Schottky barriers at the contacts of the PLED. The device model is based on the low‐density nondegenerate continuum model for the electronic structure of polymers. Polarons and bipolarons are the principal charged excitations in this model. Polarons are singly charged excitations which play the primary role in charge injection and in experiments such as internal photoemission which probe single particle interface properties. Bipolarons are doubly charged excitations which can play an important role in establishing Schottky barriers at ...

Resonant tunneling diode structures for functionally complete low power logic

Abstract: Negative-resistance resonant tunnel diodes (RTDs) perform a complete set of logic functions with a single basic configuration. Inputs feed through Schottky diodes to a transfer RTD coupled to a clocked latch having two RTDs in series. Cascaded gates are driven synchronously by multiple clock phases or by asynchronous event signals. An XOR configuration also provides logical inversion.

A unified diode model for circuit simulation

Abstract: A new commercially available diode model is described. This unified model is capable of simulating the widest range of diode technologies of any presently available. The emphasis of this paper is on describing the model's extensive features and flexibility in the different domains of operation and is of particular interest in power applications.

DC - 725 GHz sampling circuits and subpicosecond nonlinear transmission lines using elevated coplanar waveguide

Abstract: Nonlinear transmission lines (NLTL's) fabricated with Schottky diodes on GaAs were used to electrically generate 3.7-V step functions that had a measured 10%-90% fall time of 0.68 ps. These NLTL's were integrated on wafer with sampling circuits that had a measured 3-dB bandwidth of 725 GHz. Key to circuit performance are the use of low-loss, high-wave-velocity elevated coplanar waveguide transmission lines and the elimination of active device pad parasitics by contacting devices above the plane of the wafer. >

Micromachined submicrometer photodiode for scanning probe microscopy

Abstract: A submicrometer photodiode probe with a sub‐50 nanometer tip radius has been developed for optical surface characterization on a nanometer scale. The nanoprobe is built to detect subwavelength optical intensity variations in the near field of an illuminated surface. The probe consists of an Al–Si Schottky diode constructed near the end of a micromachined pyramidal silicon tip. The process for batch fabrication of the nanoprobes is described. Electrical and optical characterization measurements of the nanoprobe are presented. The diode has a submicrometer optically sensitive area with a 150 fW sensitivity.

Schottky barrier contacts of titanium nitride on n-type silicon

Abstract: Schottky contacts of TiN x thin films on n‐type Si(100) were fabricated by reactive magnetron sputtering at room temperature. In situ spectroscopic ellipsometry was used to determine the stoichiometry of the TiN x films. Dark forward bias current–voltage as well as dark reverse bias capacitance–voltage techniques was used to characterize the diodes in the temperature range from 77 to 300 K. The electrical characteristics of the contacts (i.e., barrier height, ideality factor, and leakage current) as well as the inhomogeneity of the spatial distribution of the barrier heights at the interface are improved drastically for overstoichiometric TiN x films obtained by using low negative bias voltage and/or high N2 flow rates during the TiN x deposition.

Temperature dependence and effect of series resistance on the electrical characteristics of a polycrystalline diamond metal‐insulator‐ semiconductor diode

Abstract: Temperature dependency and the series resistance effect on the electrical characteristics of a polycrystalline diamond‐based (Au/Ti)/undoped‐diamond/doped‐diamond metal‐insulator‐ semiconductor Schottky diode were investigated in a temperature range 25–300 °C. The current‐voltage (I‐V) characteristics of the device show rectifying behavior with the forward bias conduction limited by series resistance. Over the temperature range investigated, the I‐V data confirmed that the conduction mechanism of the diode is controlled by thermionic field emission. Modifying the thermionic field emission equation to include the series resistance model allows the ideality factor and barrier height of the Schottky diode to be calculated. Temperature dependence of the ideality factor and apparent barrier height was determined. By extrapolating the forward saturation current data, the evaluated ideality factor was observed to decrease from 2.4 to 1.1 while the apparent barrier increased linearly from 0.68 to 1.02 eV in the temperature range from 25 to 300 °C. The Richardson plot, ln(I0/T2) vs 103/T, has linear characteristics and indicates a true barrier height of 0.31 eV. Analysis of the temperature‐dependent series resistor measurements indicates a boron doping activation energy of 0.104 eV in the p diamond. The capacitance‐voltage‐frequency measurement confirmed that the measured capacitance varies with applied bias and frequency due to the presence of the Schottky barrier, impurity level, and high series resistance. Capacitance‐frequency measurement at zero bias indicated that the degrading capacitance at high frequency is primarily due to the high series resistance of the bulk polycrystalline diamond.

The guard-ring termination for the high-voltage SiC Schottky barrier diodes

Abstract: In this report, we propose the guard-ring structure as the edge termination for the high-voltage SiC Schottky barrier diodes. The local oxidation process is used to form the mesa of a p-n junction as the guard-ring. The comparison between the Al/Ti Schottky barrier diodes with and without the guard-ring indicates the effectiveness of the guard-ring to relax the electric field, from the results that the breakdown voltage is about two times larger with high yield. >

The barrier height and interface effect of Au-n-GaN Schottky diode

Abstract: Schottky barrier contact using Au and ohmic contact using Al were made on n-GaN grown by hydride vapour phase epitaxy. The diodes were characterized in the range 77-373 K. Under forward bias, the ideality parameter n=1.04 and the threshold voltage is 1.1 V. The reverse bias leak current is below 10-9 A on a reverse bias of -10 V. The temperature-dependence of the I-V characteristics shows two regimes of forward current transport: one at low voltage governed by thermionic emission and the high-voltage regime due to spatial inhomogeneities at the metal-semiconductor interface. The barrier height phi B and the electron affinity XS were determined to be 0.91 and 4.19 eV, respectively, by I-V measurement; and 1.01+or-0.02 and 4.09 eV, respectively, by C-V measurement. The results have been discussed.

Si/SiGe MMIC's

Abstract: Silicon-based millimeter-wave integrated circuits (SIMMWIC's) can provide new solutions for near range sensor and communication applications in the frequency range above 50 GHz. This paper presents a survey on the state-of-the-art performance of this technology and on first applications, The key devices are IMPATT diodes for MM-wave power generation and detection in the self-oscillating mixer mode, p-i-n diodes for use in switches and phase shifters, and Schottky diodes in detector and mixer circuits. The silicon/silicon germanium heterobipolar transistor (SiGe HBT) with f/sub max/ values of more than 90 GHz is now used for low-noise oscillators at Ka-band frequencies. First system applications are discussed. >

Electrical properties of Schottky barrier formed on as‐grown and oxidized surface of homoepitaxially grown diamond (001) film

Abstract: Characteristics of Schottky barriers formed on homoepitaxial diamond film have been studied. Current–voltage characteristics of Al contacts on both the as‐grown film and the oxidized film show rectification. On the other hand, ohmic property is observed on Au/as‐grown film while Au/oxidized film shows rectification. These results imply that the mechanism of the barrier formation on the as‐grown diamond is drastically changed by oxidation. The difference of electrical properties between the as‐grown film and the oxidized film is also observed from capacitance–voltage characteristics. This result suggests that additional acceptors which are not related to boron, exist in the as‐grown film and disappear after oxidation.

Schottky-based band lineups for refractory semiconductors

Abstract: An overview is presented of band alignments for small-lattice parameter, refractory semiconductors. The band alignments are estimated empirically through the use of available Schottky barrier height data, and are compared to theoretically predicted values. Results for tetrahedrally bonded semiconductors with lattice constant values in the range from C through ZnSe are presented. Based on the estimated band alignments and the recently demonstrated p-type dopability of GaN, we propose three novel heterojunction schemes which seek to address inherent difficulties in doping or electrical contact to wide-gap semiconductors such as ZnO, ZnSe, and ZnS.

On the modeling and optimization of Schottky varactor frequency multipliers at submillimeter wavelengths

Abstract: Schottky varactor frequency multipliers are used to generate local oscillator power at millimeter and submillimeter wavelengths. The equivalent circuit of the Schottky varactor contains a junction capacitance, a junction conductance, a series resistance and a model for electron velocity saturation. At millimeter wavelengths the equivalent circuit is affected by the edge effects, which are due to the small-area circular anode. The correction factors due to the edge effect for the junction capacitance and for the series resistance are available in the literature. In this work the electron velocity saturation is modeled by limiting the velocity of the transition front between the depleted and undepleted layer. By using this model the maximum current of the diode is given by the actual area of the transition front between depleted and undepleted layers, and is therefore related to the capacitance correction factor. The new model has been tested by analyzing a two diode balanced doubler for 160 GHz presented earlier in the literature. The agreement between the theoretical results and the measurements is excellent. The new diode model is useful in optimization of varactors for high millimeter and submillimeter wave frequencies. >

Field-dependent permittivity in metal-semiconducting SrTiO3 Schottky diodes

Abstract: The field dependence of the dielectric constant of SrTiO3 is investigated using the capacitance versus bias voltage characteristics of various metal‐SrTiO3:Nb Schottky diodes. The relative dielectric constant is shown to decrease one order of magnitude for electric fields ranging from 0.1 to 10 MV/cm. At low fields the permittivity follows the Curie–Weiss law, whereas at fields larger than 500 kV/cm the permittivity is nearly temperature independent. At high doping densities the field dependent permittivity gives rise to a reduction of the depletion width of the Schottky diode.

Schottky contacts on a highly doped organic semiconductor

Abstract: Schottky-diode action in thiophene oligomer is investigated by current-density--voltage (J-V) and capacitance-voltage (C-V) measurements. An energy-band diagram is deduced that explains the diode characteristics for both unintentionally and highly doped thiophene oligomers. We conclude that the diode consists of a thin layer of low ionizable acceptor density (${\mathit{p}}^{\mathrm{\ensuremath{-}}}$) at the metal-oligomer interface and a semiconductor bulk layer that has a higher dopant concentration (${\mathit{p}}^{+}$). The presence of the lower doped ${\mathit{p}}^{\mathrm{\ensuremath{-}}}$ layer leads to a built-in voltage of 0.5 V, which is both experimentally observed and predicted using standard Schottky theory. Differences in J-V characteristics upon doping the thiophene semiconductor are explained by the Schottky-barrier lowering effect for the reverse current density, and by a higher conductivity of the bulk for the forward current density.

Direct current conduction properties of sputtered Pt/(Ba0.7Sr0.3)TiO3/Pt thin films capacitors

Abstract: Current flow through Pt/(Ba0.7Sr0.3)TiO3/Pt stack consists of both polarization current and electronic leakage current, which were separated by monitoring the discharging current when applied voltage was turned off. Electronic current comes from electrical field enhanced Schottky emission at the electrode–dielectric interface, and dominates the current flow at high electric field. At low electric field, polarization current prevails. The voltage and time dependence of the polarization current can be modeled by a distribution of Debye‐type relaxations. The relaxation time and capacitance derived from current–time measurements were applied to simulate the current–voltage behavior, where good fitting to experimental result was obtained.

Manufacturing method of SiC Schottky diode

Abstract: A Schottky electrode is formed on an n-type SiC base member with an Al--Ti alloy or by laying Al films and Ti films alternately, and a resulting structure is subjected to a heat treatment of 600° C. to 1,200° C. A p-type SiC layer may be formed around the Schottky junction so as to form a p-n junction with the n-type SiC base member.