Showing papers on "Schottky diode published in 1974"

Harmonic Mixing with an Anti-Parallel Diode Pair

Abstract: An analytical and experimental investigation of the properties of an antiparallel diode pair is presented. Such a configuration has the following unique and advantageous characteristics as a harmonic mixer: 1) reduced conversion loss by suppressing fundamental mixing products; 2) lower noise figure through suppression of local oscillator noise sidebands; 3) suppression of direct video detection; 4) inherent self protection against large peak inverse voltage burnout. These results are obtained without the use of either filters or balanced circuits employing hybrid junctions.

High-speed integrated logic with GaAs MESFET's

Abstract: The feasibility of using GaAs metal-semiconductor field-effect transistors (GaAs MESFET's) in fast switching and high-speed digital integrated circuit applications is demonstrated. GaAs MESFET's with 1-/spl mu/m gate length are shown to have a current-gain-bandwidth product f/SUB T/ equal to 15 GHz. These devices exhibit a 15 ps internal delay in a large-signal switching test. A simple logic circuit consisting of MESFET's and Schottky diodes was monolithically integrated on a semiinsulating GaAs substrate. This logic circuit exhibits a propagation delay of 60 ps with no output load, and 105 ps when its output is loaded by three similar logic gates. A useful bandwidth of approximately 3 GHz is observed.

The role of the metal-semiconductor interface in silicon integrated circuit technology

Abstract: A typical medium-scale integrated (MSI) circuit requires hundreds of metal-semiconductor (M–S) junctions that are utilized for rectification, interconnection of device elements, and termination to external circuits. Comparison has been made between two metallization technologies, based upon the possible metallurgical reactions with Si: (1) nonreactive, such as evaporated aluminum, and (2) reactive, such as PtSi. Ohmic and rectifying contacts have been contrasted on the basis of the dominant current conduction mechanisms at the M–S interface. Current transport has been characterized in terms of the height and thickness of the potential energy barrier arising from thermal equilibrium among charge carriers between dissimilar conductors. Thermionic emission of electrons and holes provides the first illustration of conduction over a thick potential barrier (≫100 A), resulting in a rectifying contact (Schottky barrier diode). Thus, Schottky diode currents are exponentially dependent upon potential barrier height and inverse temperature. The contrasting illustration deals with a thin barrier (≪100 A) that conducts electrons and holes by quantum mechanical tunneling and forms ohmic contacts with resistance controlled only by contact size and underlying silicon resistivity. The final section covers two possible problems associated with silicon integrated circuit (SIC) fabrication. In the first example, a layer of oxide, too thin to be visible by optical interference (<500 A), can prevent proper contact formation. A method of observation, which makes use of hydrostatic surface tension, has been presented with experimental results on SiO2 films. Successive etching has revealed a detection limit of 11–13 A. The second deleterious phenomenon to be treated is the electrical degradation of Schottky barrier rectification associated with nonplanar penetration of metals into silicon. The destruction of the planar M–S interface could result from either undesired alloy eutectics or metallic precipitation.

Interface and doping profile characteristics with molecular‐beam epitaxy of GaAs: GaAs voltage varactor

Abstract: Studies of the doping profile characteristics of molecular‐beam epitaxy (MBE) of GaAs on GaAs substrates are reported. Highly resistive regions at the substrate—epitaxial‐layer interface, and within the epitaxial layer, may occur if the growth is interrupted. It is shown that almost any arbitrary voltage dependence of the capacitance of such structures can be achieved by varying the dopant deposition rate during epitaxy. To illustrate the versatility of this growth technique, voltage‐variable capacitors have been prepared with Schottky barriers on MBE GaAs layers with precisely controlled doping profiles. Low‐frequency measurements (up to 100 MHz) demonstrate that capacitance variations in excess of a factor of 10 have been achieved by varying the applied bias voltage V from 0.3 V (with no significant forward conduction) to −1.0 V. The feasibility of frequency tuning diodes with C−1/2[sine wave]φ−V, where φ is the effective barrier height, is shown. At ‐3 V bias, cutoff frequencies >40 GHz have been measu...

Submillimeter detection and mixing using Schottky diodes

Abstract: Schottky diodes have been used for the first time as harmonic mixers in the 0.1–1.0‐mm wavelength region. Beat notes between the 33rd harmonic of a 74‐GHz V‐band klystron and 118.8‐μ laser radiation are observed directly without the need of narrow‐band synchronous detection. The demonstrated performance of these room‐temperature diodes as wide‐band or heterodyne detectors of submillimeter radiation and their rugged construction make them superior to current point contact devices.

Metal-silicide Schottky diode employing an aluminum connector

Abstract: In a Schottky diode of the type wherein a metal silicide layer interfaces with a silicon semiconductive body to form a Schottky diode, an inert barrier layer of a refractory metal, such as Mo, Ti, W, Ta and alloys thereof, is deposited overlaying and in electrical contact with the metal silicide layer An aluminum electrical connector electrode is deposited overlaying the barrier layer for intraconnecting the Schottky diode with other devices The refractory barrier layer prevents the aluminum from diffusing into or otherwise reacting with the metal silicide layer in such a way as to deleteriously affect the performance of the Schottky diode

An 8% efficient layered Schottky‐barrier solar cell

Abstract: An 8.1% efficient 1‐cm2 Schottky‐barrier solar cell has been fabricated in our laboratory using a layered Schottky barrier on 2‐Ω cm p‐type silicon. Reproducible results have been obtained on the layered structure which involves 44‐A Cr adjacent to the silicon to obtain good photovoltaic voltage and a 58‐A Cu overlayer to decrease cell resistance. The layered structure provides good control of barrier height, resistance, and optical transmission. Application of this approach should produce a 15% efficient Schottky solar cell and be readily applied to thin‐film silicon solar cells when high‐quality thin silicon films have been developed.

A simplified self-consistent model for image force and interface charge in Schottky barriers

Abstract: Some qualitative features are shown for an electrostatically self-consistent solution, initially without correlation and exchange forces, for the effect of electrons which tunnel from the metal of a Schottky barrier into the energy band gap of the semiconductor. The effect of an incremental electric field in the bulk semiconductor is deduced from a simple analytical treatment. In covalent semiconductors most of the incremental electric field terminates in the semiconductor in a manner almost independent of the nature of the metal, i.e., the effective “metal” electrode exists inside the bulk semiconductor. This is not true for ionic semiconductors. When the “metal” electrode location is used as the origin for the image force, a normal square root of the field dependence of the Schottky image force lowering is predicted at low electric fields and a linear dependence is predicted at high electric fields, both as reported recently by Andrews. The model also predicts the order of magnitude of the very small ba...

Use of Schottky‐diode collectors for SEM determination of bulk diffusion lengths

Abstract: Schottky diodes were used as collectors in the determination of bulk hole diffusion lengths (Lhn) by means of a scanning electron microscope in the beam‐induced current mode The scans were performed on cross sections obtained by cleavage along a plane perpendicular to the metal layer For n‐type GaP this technique yields excellent results

Concentration dependence of the minority carrier diffusion length and lifetime in GaP

Abstract: The minority carrier diffusion length and lifetime have been determined in Zn-doped p-type and in undoped and S-doped n-type GaP grown by liquid phase epitaxy, from the spectral response of Schottky diodes, and the decay of cathodoluminescence respectively. Below 1018 cm−3 the quantities are independent of donor or acceptor concentration, and typical values are 6 μm and 120 ns in n-type, and 3 μm and 30 ns in p-type material. At higher concentrations the values fall rapidly. Electron injection efficiencies in p-n junctions are calculated from the data and are in agreement with diode efficiency measurements. The electron injection efficiency is shown to be a maximum at a donor concentration of 1×1018 cm−3 for a typical lamp structure. Diffusion length can also be derived from the variation of photocurrent with diode capacitance, but low values are obtained. The divergence is explained in terms of recombination in the space-charge layer.

Phenomenology of metal-semiconductor electrical barriers

Abstract: The phenomenological rules governing the values of electrical barriers between metals, and semiconductors or insulators are reviewed. The barrier energies on ionic insulators are shown to vary strongly with metal electronegativity, while in the case of covalent semiconductors, the barrier energies are relatively independent of the metal. The barrier energy from the metal Fermi level to the conduction band of the semiconductor is shown to be approximately two thirds of the semiconductor band gap with certain exceptions. The success of a simple barrier model in accounting for the properties of the barrier are reviewed. The variation of barrier energy with electrical field is reported for Al-SiO2, Al-GaSe, and Al-GaAs and compared with simple theory including image-force lowering and field penetration into the metal. Transport through interfacial barriers is illustrated by discussing transport through metal-GaSe-metal structures and metal-InAs Schottky barriers.

cw generation of tunable narrow-band far-infrared radiation

Abstract: Tunable narrow‐band cw generation of far‐infrared radiation has been achieved for the first time in the 70‐μm to 1‐mm wavelength region by noncollinear difference‐frequency mixing of two single‐mode CO2 lasers in GaAs at 80 K. Using a Schottky diode as a heterodyne harmonic mixer with a carcinotron local oscillator, the far‐infrared signal is shown to have a linewidth of less than 100 kHz and a fine tuning capability in excess of 50 MHz.

Submillimeter Heterodyne Detection and Harmonic Mixing Using Schottky Diodes

Abstract: Schottky diodes have been used for submillimeter , heterodyne detection and harmonic mixing. Using a carcinotron local oscillator at 890 mu m, sensitive detectors of optically pumped lasers have been demonstrated up to fifth harmonic mixing at 1757.5 GHz. The measured noise equivalent power (NEP) in fundamental mixing is approximately 10/sup -16/ W/Hz.

Schottky barriers and plasmons

Abstract: The changes in the electron exchange and correlation potential are related to the collective excitation at the interface of a metal semiconductor junction. They are shown to change discontinuously across the band gap, and the possible effects on the barrier formation are discussed. The possibility of surface superconductivity through exciton and plasmon exchange is considered briefly.

Electrical conduction in reactively sputtered tantalum oxide thin films

Abstract: High-field electrical conduction over a temperature range of 303-363 K has been studied in sandwich structures of Al/Ta2O5/Al and Al/Ta2O5/Ta in the thickness range 400-900 nm. The oxide film was produced by reactively sputtering a tantalum target in a mixture of argon and oxygen. No marked rectification was observed in the samples and it was observed that the conduction process bore strong resemblance to either a Poole-Frenkel or a Schottky mechanism, the results showing a definite lowering of the activation energy for the conduction process with field. Detailed analysis of the data suggest an electrode-limited mechanism such as that suggested by Schottky.

Monolithic semiconductor rectifier circuit structure

Abstract: A monolithic semiconductor rectifier circuit structure incorporating two npn power transistors and two Schottky-barrier diodes is disclosed. The transistors are connected in an inverted mode and are the main rectifying elements. The Schottky-barrier diodes are connected between the emitters and collectors of the respective transistors and help to initiate rapid turn-on of the transistors. The Schottky-barrier diodes have a relatively low forward voltage drop and their reverse recovery currents are substantially zero. Thus, the Schottky diodes operate with minimum power loss. The monolithic circuit structure may be combined with a discrete current transformer unit to form a hybrid rectifying circuit.

GaAs Schottky&#8212;Read diodes for x-band operation

Abstract: High-efficiency performance of GaAs Schottky-Read IMPATT diodes has been observed at X-band frequencies. The highest efficiency measured was 26.1 percent with 2.5-W continuous-wave (CW) output power at 8.8 GHz for a single-mesa diode while multiple-mesa diodes have delivered more than 7 W at X band. The diodes were fabricated from multiple-layer epitaxial material with gold-plated heat sinks. Details of materials preparation and diode fabrication are presented. Theoretical calculations of diode breakdown voltage and efficiencies have been made as a function of the structural properties of the diodes. Good agreement has been obtained between the experimental microwave oscillator performance and the theoretical calculations.

High-temperature stability of Au Pt/n-GaAs Schottky barrier diodes

Abstract: The operating surface temperature for the Au/Pt/ n -GaAs Schottky barrier microwave devices is in the temperature range of 200–250°C. In order to determine operating lifetimes for these devices accelerated aging studies were performed. In this study the reverse bias voltage at currents of 10 μA, 100 μA and 1 mA were determined as a function of annealing time at 350°C for diodes metallized with AuPt and with Pt alone. Two distinct degradation mechanisms were observed. (a) Penetration of Au by diffusion through thin Pt films or by surface migration along edges or cracks in the Pt films resulted in rapid degradation of the devices. (b) The second degradation mechanism was observed in absence of Au and was found to be related to annealing ambient and the metallurgical interaction between Pt and GaAs. A decrease in the reverse bias voltage was observed due to the diffusion of oxygen from the interfacial oxide and from the ambient. Oxygen from the ambient diffused throug platinum into GaAs and was the cause of the final degradation of devices annealed in air. An increase in the reverse bias voltage occurred immediately after the initial decrease due to the interfacial oxide. This recovery has been attributed to the metallurgical interaction between Pt and GaAs which led to the formation of PtAs 2 at the interface and GaPt phases away from the interface.

Electronic properties of undoped polycrystalline silicon

Abstract: Standard semiconductor measurements and techniques have been applied to undoped, high-purity polycrystalline silicon to determine its electronic properties. Resistivity and Hall mobility were determined as function of temperature, and the ability of polycrystalline silicon to form Schottky barriers and p−i−n junctions has been evaluated experimentally. Present results show Si grain boundaries behaving as p-type layers separating high-resistivity grains. An effective mobility, half the monocrystalline value, and an average carrier density in the 1015 cm−3 range are deduced. A qualitative model is discussed to describe present results.

Bias-dependent small-signal parameters of Schottky contact microstrip lines

Abstract: Schottky contact lines are a type of microstrip on semiconducting substrata. The strip forms a rectifying metal-semiconductor interface, the Schottky contact. Schottky contact lines show interesting small-signal and large-signal properties, so far unknown in microwave IC-technology, due to the voltage-dependent capacitance per unit length. In this paper the small-signal transmission line properties are investigated. Formulas for the characteristic impedance and the propagation constant are given. Particular account is taken of the effect of varying external d.c. bias. measurements performed on microstrip lines with Al- and Au-Schottky contacts on n -type silicon are given.

High performance GaAs quasi-planar varactors for millimeter waves

Abstract: A novel quasi-planar and highly reliable varactor configuration has been developed to batch fabricate fully passivated GaAs Schottky varactors with near ideal characteristics and state of the art performance Typically, they exhibit at zero bias a junction capacitance of 012 pF and a cutoff frequency in excess of 700 GHz when measured at 70 GHz As frequency doublers (∼ 35 to 70 GHz) and triplers (35 to 105 GHz), efficiencies greater than 40 and 25 percent, respectively, have been achieved In a parametric amplifier pumped at 105 GHz and operated in the 55- to 65-GHz signal frequency band, a gain of 14 dB, a 1-dB bandwidth of 670 MHz, and a single sideband noise factor of 59 dB were achieved

Schottky barrier diode contacts

Abstract: A Schottky barrier contact includes a thin layer of high carrier concentration impurities ion implanted over the contact surface of the semiconductor. This reduces the electronic barrier height, increases the tunneling component, and thus reduces the forward-bias turn-on voltage of the diode. The implanted layer has a carrier concentration at least ten times that of the semiconductor substrate, and a thickness smaller than the width of the inherent depletion region resulting from the internally generated electric field at the metal-semiconductor interface. An implanted layer of the opposite conductivity type raises the barrier height.

Semiconductor I.C. with protection against reversed power supply

Abstract: A semiconductor integrated circuit includes an integrated resistor body of one conductivity type being contained in a lightly doped pocket of the opposite conductivity type. A metal contact is made to a surface portion of the lightly doped pocked forming a Schottky diode. The metal contact is connected to the hot (Vcd) power supply terminal and thus the diode is normally forward biased. When the power supply is inadvertently reversed, the Schottky diode is reverse biased and prevents destructive currents from flowing in a forward biased p-n isolation junction between the substrate and the pocket.

Low-Noise Diodes and Mixers for the 1--2-mm Wavelength Region

Abstract: Ultralow capacitance low-noise Schottky-barrier diodes have been developed for use in the 1--2-mm-wavelength region. The diodes have been fabricated using both photolithographic and electron-beam lithographic techniques. Use of the latter technique to make diodes shaped as crossed stripes of width 0.25 mu m and 0.4 mu m on epitaxial GaAs resulted in a 30-percent reduction in spreading resistance over that of photolithographically formed circular diodes with approximately the same junction area and capacitance. Because of this reduction, it is suggested that in order to minimize receiver noise figure at frequencies greater than about 200 GHz, it will prove advantageous to use such shaped diodes rather than the conventional circular ones. The diodes were used in mixers operating at 140, 175, and 230 GHz. At 140 and 175 GHz the diodes were mounted in conventional Sharpless wafers. At 230 GHz, in addition to Sharpless wafers, a mixer of unique design was used which incorporated an RF matching element, low-pass filter, and IF output transmission line, all on stripline, whose performance was optimized using low-frequency scaling techniques. Mixer double side-band (DSB) noise figures of 3.8, 8.1, and 12.6 dB were measured at the three frequencies, respectively. At 175 and 230 GHz, however, mixer performance is degraded due to a lack of sufficient local oscillator (LO) power and this is currently the principal limitation to their performance.

Properties of Schottky barriers and p‐n junctions prepared with GaAs and Alx Ga1−x As molecular beam epitaxial layers

Abstract: The properties of molecular beam epitaxy (MBE) that are relevant to device applications have been investigated. Precise control of layer thickness is one of the most attractive features of MBE, and layers from a few hundred angstroms to 10 μ may readily be grown. Unintentionally doped GaAs layers grown on 〈100〉‐oriented substrates are n type, and room‐temperature carrier concentrations of ∼2 × 1015 cm−3 with a mobility of ∼6000 cm2/V sec have been obtained. Schottky barriers on MBE n‐type GaAs layers demonstrate that defect‐free devices with uniform properties may be prepared at the present time. Junctions of p‐ and n‐type MBE have also been fabricated and have been found to compare favorably with p‐n junctions prepared by other techniques. Heterojunctions of GaAs and Alx Ga1−xAs have also been prepared and evaluated. The p‐type Alx Ga1−xAs layers are suitable for heterostructure applications, while n‐type Alx Ga1−xAs layers tend to be high resistivity at the present time.

Forward I-V characteristics of Pt/n-GaAs Schottky barrier contacts

Abstract: The forward I-V characteristics of Pt/n-GaAs planar Schottky diodes and the effect of high temperature annealing on these characteristics have been investigated. Near-ideal (thermionic emission theory) I-V characteristics with an ideality factor n ≈ 1·00–1·09 and a barrier height φB ≈ 0·90–0·95 V are obtained for diodes made on as-received GaAs. On annealing at 350°C in vacuum, n remains practically unchanged although φB increases by ≈ 5–6 per cent and rather large currents are detected at voltages <0·3 V, which are attributed to the recombination centers created during alloying. For diodes made on GaAs which was preannealed in air at 350°C, non-ideal behavior is observed with φB ≈ 0·79–0·80 V and n ≈ 1·29. After annealing at 350°C in vacuum, n gradually decreases to 1·07 whereas φB increases to 0·96 V. Recombination currents are now observed at lower voltages. After further annealing at 350°C in air, n increases, φB decreases and recombination currents at lower voltages are no longer observed. A mechanism is proposed to explain the observed forward I-V characteristic behavior.

Compensated monolithic integrated current source

Abstract: A main semiconductor element is placed on a circuit chip; additionally, a compensating semiconductor element is placed thereon, the compensating semiconductor element being a diode, a substrate diode, a Schottky diode, a transistor with shortcircuited base emitter junction, open base transistor, or a resistor, the additional semiconductor element having one terminal connected to the main semiconductor and the other terminal either to the substrate or to a source of potential at least as large as the potential of the main element. The leakage current to be bypassed may affect the main element directly, particularly when the main element is operated in digital on-off mode, or indirectly by passing a compensating current which affects another element such as an operational amplifier, or provides directly for additional current compensating for leakage current of the main element. Placing the additional element on the same substrate and making the element of approximately the same surface extent provides for comparable passage of compensating leakage current over a wide range of semiconductor crystal temperatures.

Integrated circuit memory cell

Abstract: A cell for an integrated circuit memory is formed of two interconnected identical halves. Each such half is integrally formed without surface metal interconnections. The memory is fabricated from a semiconductor body which comprises an epitaxial layer of one conductivity type overlying a semiconductor substrate of the opposite type. Each half comprises a vertical npn transistor having the collector thereof at the exposed surface of the epitaxial layer and a lateral current source transistor. The collector region of each vertical transistor has two metal contacts, one to form a Schottky diode to couple to a bit line, and one to form an ohmic connection for crosscoupling of the two halves. Power is distributed by a line diffused in the epitaxial layer which line comprises the emitters of the lateral current source transistors and power is returned through word lines which are formed in the substrate of the body prior to growth of the epitaxial layer.

Substrate fed logic - An improved form of injection logic

Abstract: A novel form of integrated injection logic is described which has significant advantages over its conventional counterpart in packing density and power-delay product. The structure is formed from two epitaxial layers on a heavily doped p type sub-strate. The p type epitaxial layer, which forms the base of the npn transistor, is lightly doped, allowing the fabrication of Schottky contacts. This gives rise to an extremely powerful multi-input, multi-output logic element on a single base land. The fundamental SFL structure has been successfully demonstrated. Gates and a ring oscillator have been operated and a reduction in power-delay product has been shown. A viable technology for Schottky Barrier Diodes has been demonstrated and an optimised structure has been designed.

Large Area Reach-Through Avalanche Diodes for Radiation Monitoring

Abstract: Avalanche diodes, up to 20 mm2 in area, have been made with sensitivities up to 6 × 106 counts/ Roentgen. Operating at 200 volts, typical gains of 20 are achieved. This permits the detection of 6 keV X-rays and dosimetry of gamma rays down to 30 keV with background counting rates of about 0.1 c/s.