Showing papers on "Diode published in 1995"

Selectively oxidised vertical cavity surface emitting lasers with 50% power conversion efficiency

Abstract: Index-guided vertical cavity top-surface emitting laser diodes have been fabricated from an all epitaxial structure with conducting mirrors by selective lateral oxidation of AlGaAs At low voltage, a 78% slope efficiency, and a 350 mu A threshold current in a single device combine to yield a maximum power conversion efficiency of 50% at less than a 2 mA drive current The device operates in a single mode up to 15 mW >

Method for producing high efficiency light-emitting diodes and resulting diode structures

Abstract: A method of producing light emitting diodes from silicon carbide with increased external efficiency is disclosed which includes directing a beam of laser light at one surface of a portion of silicon carbide, and in which the laser light is sufficient to vaporize the silicon carbide that it strikes to thereby define a cut in the silicon carbide portion; and then dry etching the silicon carbide portion to remove by-products generated when the laser light cuts the silicon carbide portion. The resulting wafer and diode structure are also dislcosed.

High brightness electroluminescent device emitting in the green to ultraviolet spectrum and method of making the same

Abstract: A green-blue to ultraviolet light-emitting optical device, e.g. a green-blue to ultraviolet emitting laser or a green-blue to ultraviolet emitting diode, comprising a green-blue to ultraviolet light emitting gallium nitride material on a base structure including a silicon carbide substrate, which preferably consists of 2H-SiC, 4H-SiC, or a-axis oriented 6H-SiC. The carrier mobility and the transparency of the silicon carbide substrate are optimized by the selection of orientation and polytype, thus enhancing device performance. The light-emitting diodes may incorporate a structural modification to increase the light output comprising a dielectric Bragg mirror beneath the LED structure, made of alternating layers of AlN, GaN, InN or their alloys. Methods for making such light-emitting diodes are provided, including a technique for defining individual devices by mesa etching which avoids possible damage to the active area during dicing.

Micrometer- and Nanometer-Sized Polymeric Light-Emitting Diodes

Abstract: A method for the fabrication of micrometer-and submicrometer-sized polymeric light-emitting diodes is presented. Such diodes have a variety of applications. Light sources of dimensions around 100 nanometers are required for subwavelength, near-field optical microscopy. Another possible application is patterning on the micrometer and nanometer scale. The diodes have been made in the form of a sandwich structure, with the conductive polymer poly(3,4-ethylene-dioxythiophene) polymerized in the pores of commercially available microfiltration membranes defining the hole-injecting contacts, poly[3-(4-octylphenyl)-2,2;-bithiophene] as the light-emitting layer, and a thin film of calcium-aluminum as the electron injector.

Thin-film nonlinear optical diode

Abstract: We present results of a theoretical investigation into a nonlinear thin‐film multilayer device that exhibits passive anisotropic optical transmission—the analogue of the electronic diode. This optical diode is a nonlinear, asymmetric, distributed Bragg reflector. Material parameters for a nonlinear polymer (polydiacetylene 9‐BCMU) and rutile are used in alternating layers to model a realistic device. The diode exhibits more than five times as much transmittance in one direction as in the opposite direction. It has a thickness of only 2 μm and is polarization insensitive.

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.

Bilayer composite electrodes for diodes

Abstract: An ohmic hole injecting electrode or contact (110, 112) for diode structures is disclosed. It is formed of multilayer composite materials (110, 112) and gives superior results in this application. The composite materials include a layer of a high work function inorganic material (112) and a layer of conductive polyaniline ('PANI') (110). In preferred embodiments (140), the anode has substantial transparency. These preferred materials can function as transparent electrodes in light-related diodes such as LEDs and photovoltaic cells where they exhibit lower turn on voltages and higher efficiencies.

Introduction to electronic devices

Abstract: Basics of Quantum Mechanics. Basics of Solid State Physics. Electrons and Holes in Semiconductors. Diodes and Contacts. Bipolar Junction Transistors. MOSFETs. Compound Semiconductor FETs and Thin Film Transistors (TFTs). Photonic Devices. Device Fabrication and Novel Devices. Appendices. Glossary. Index.

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.

Unitary lens semiconductor device

Abstract: A unitary lens semiconductor device and method. The unitary lens semiconductor device is provided with at least one semiconductor layer having a composition varying in the growth direction for unitarily forming one or more lenses in the semiconductor layer. Unitary lens semiconductor devices may be formed as light-processing devices such as microlenses, and as light-active devices such as light-emitting diodes, photodetectors, resonant-cavity light-emitting diodes, vertical-cavity surface-emitting lasers, and resonant cavity photodetectors.

Optical device with low electrical and thermal resistance bragg reflectors

Abstract: A compound-semiconductor optical device and method. The optical device is provided with one or more asymmetrically-graded heterojunctions between compound semiconductor layers for forming a distributed Bragg reflector mirror having an improved electrical and thermal resistance. Efficient light-emitting devices such as light-emitting diodes, resonant-cavity light-emitting diodes, and vertical-cavity surface-emitting lasers may be formed according to the present invention, which may be applied to the formation of resonant-cavity photodetectors.

Method and structure for providing ESD protection for silicon on insulator integrated circuits

Abstract: A method and structure for providing ESD protection for Silicon-On-Insulator (SOI) integrated circuits. The ESD protection circuit includes an electrically conductive pad and first conductor segment fabricated over an insulating layer. The first conductor segment connects the pad directly to a first node, without an intervening input resistor. A first diode is fabricated over the insulating layer and connected between the first node and a first voltage supply rail. Similarly, a second diode is fabricated over the insulating layer and connected between the first node and a second voltage supply rail. Ballast resistors can be included in series with each of the diodes. A cross power supply clamp, also fabricated over the insulating layer, is connected between the first and second voltage supply rails. The first node of the ESD protection circuit is coupled to the SOI integrated circuit to be protected. The ESD protection circuit can be fabricated on a minimum number of silicon islands to improve local thermal spreading. Improved ESD protection is provided to input, output, and I/O pins of an SOI integrated circuit, while promoting high speed signal transfer between these pins and the integrated circuit.

Semiconductor diode with silicide films and trench isolation

Abstract: The invention comprises a diode in a well having trench isolation that has an edge. Both the well contact of the diode and the rectifying contact of the diode are silicided, but the silicide on the rectifying contact is spaced from the trench isolation edge. The spacing is provided by a gate stack or other mask. In one embodiment, the gate stack alone spaces the two diode contacts from each other, eliminating the need for trench isolation therebetween. The structure reduces diode series resistance and silicide junction penetration. It significantly improves heat flow in trench isolation technologies, increasing the level of ESD protection. The invention also comprises an SOI diode having a lightly doped region in the thin layer of semiconductor under a gate stack with an ohmic contact to the lightly doped region self-aligned to an edge of the gate stack.

Cold Electron Emission from Electroluminescent Porous Silicon Diodes

Abstract: It is demonstrated that electroluminescent porous silicon (PS) diodes operate as surface-emitting cold cathodes The PS diode is composed of a semitransparent thin Au film, PS layer, n-type Si substrate and ohmic contact When a sufficient positive bias voltage is applied to the Au contact in vacuum, the diode uniformly emits electrons as well as visible light This cold emission is explained by the model that electrons are injected from the substrate, drifted by the field within the PS layer, and ejected as hot electrons through the thin Au film This mode gives important insight for understanding the electroluminescence mechanism of PS, and shows the potential of PS devices not only for optoelectronic applications, but also for vacuum microelectronic ones

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.

Effects of doping in polymer light‐emitting diodes

Abstract: We observed a dramatic improvement in the performance of polymer light‐emitting diodes (LEDs) upon light doping of the organic layer. The LEDs betrayed symmetrical electrical and light‐emission characteristics. Their turn‐on voltage is lower and their external quantum and power conversion efficiencies are higher by nearly an order of magnitude when compared with devices that utilized a nominally undoped organic layer. We attributed these results to the modification of the tunneling barrier in metal–polymer–metal junctions due to the presence of an induced polarization electric field associated with the ionized dopant counterions and charged polymer chains.

Voltage controlled oscillator band switching technique

Abstract: A band switchable resonant circuit for a voltage controlled oscillator has an inductive component in parallel with a plurality of varactor diodes. Some of the varactor diodes are selectively switchable to control the frequency range of circuit operation.

Device for protecting a secondary battery from overcharge and overdischarge

Abstract: A device for protecting a secondary battery from overcharge and overdischarge has two switches and two diodes respectively connected in parallel with the switches. Each diode is conductive in the same direction as a parasitic diode included in the associated switch. When one of the switches is turned off, a current flows through the diode connected to the switch prior to the parasitic diode of the switch. This prevents a current from flowing through the switch in the opposite direction. The switches are, therefore, free from deterioration and damage and allow the protection device to surely operate without being damaged. Alternatively, a charge path and a discharge path may be connected in parallel with each other, and each may have a serial connection of a switch and a diode opposite in direction to a parasitic diode included in the switch. In this case, when one of the switches assigned to the respective paths is turned off, a current flows through the other path prior to the parasitic diode of the switch turned off.

Multilayer solar cells with bypass diode protection

Abstract: A multilayer solar cell with bypass diodes includes a stack of alternating p and n type semiconductor layers (10, 11, 12, 13, 14) arranged to form a plurality of rectifying photovoltaic junctions (15, 16, 17, 18). Contact is made to underlying layers by way of a buried contact structure comprising groves extending down through all of the active layers, the walls of each groove being doped (33, 34) with n-or p-type impurities depending upon the layers to which the respective contact is to be connected and the grooves being filled with metal contact material (31, 32). One or more bypass diodes are provided by increasing the doping levels on either side (10, 13) of one or more portions of the junctions (16) of the cell such that quantum mechanical tunnelling provides a reverse bias characteristic whereby conduction occurs under predetermined reverse bias conditions. Ideally, the doping levels in the bypass diodes is 1018 atoms/cm3 or greater and the junction area is small.

Microwave and Millimeter-Wave Diode Frequency Multipliers

Abstract: Operating Principles and Basic Limitations of Diode Frequency Multipliers. Semiconductor Diodes for Frequency Multipliers. Basic Diode Frequency Multiplier Circuits. Nonlinear Analysis. Optimization of Diode Frequency Multiplier Operating Conditions. Linear and Noise Analysis. Transmission Lines, Waveguides and Components: Transmission Lines and Waveguides. Practical Microwave and Millimeter-Wave Frequency Multipliers.

Charge pump circuit for high side switch

Abstract: A high side monolithic switching circuit integrated into a silicon chip is described in which the charge pump is connected to the ground terminal by a constant current circuit and floats relative to the ground terminal to reduce noise generation The charge pump is connected to a V cc terminal by an auxiliary power MOSFET having its gate connected to the charge pump output circuit The conventional charge pump diodes are implemented as MOSFET devices which can be easily integrated into the common monolithic chip A clamping circuit across the charge pump permits the use of a low voltage, small area capacitor for a high voltage device

Multi-beam optical system using lenslet arrays in laser multi-beam printers and recorders

Abstract: A multi-beam laser printer for printing on light-sensitive thermal media where a monolithic array of independently modulated diode lasers (13) is used to reduce the size of the printer. A closely spaced array of printing spots (26) is produced from the separate diode lasers using two lenslet arrays (21,34) having power in the array direction. To correct for non-straightness of the laser array, an optical arrangement is used to conjugate the far field of the lasers in a direction perpendicular to the array direction of the printing plane so that the laser array produces a straight line of printing spots on the light-sensitive medium. The second lenslet array avoids vignetting.

Electrostatic discharge protection device for integrated circuit

Abstract: An electrostatic discharge (ESD) device includes a pair of depletion mode MOSFETs connected drain-to-drain in a series path between an input terminal and an output terminal, the gate of each MOSFET being connected to its source. A first diode having a relatively high breakdown voltage is connected between ground and the common drain terminal of the MOSFETs, and a second diode having a relatively low breakdown voltage is connected between ground and the output terminal of the device. The second diode breaks down during a relatively low, long-lived voltage spike (in an automobile, sometimes referred to as a "load dump"), while the second MOSFET saturates, limiting the size of the current through the second diode. The first diode breaks down during a large voltage spike of short duration, such as occurs from an ESD.

In0.53Ga0.47As/AlAs resonant tunnelling diodes with switching time of 1.5 ps

Abstract: Switching times of 1.5 ps for In0.53Ga0.47As/AlAs resonant tunnelling diodes (RTDs) with 1.1 nm wide barriers and a peak current density of 6.8 × 105 A/cm2 are reported. To the authors' knowledge, this is the fastest switching ever reported for any type of RTD. The authors confirm that the obtained switching time is close to the value calculated from the experimentally derived depletion-layer capacitance and average negative differential resistance.

Novel cathode for field-emission applications

Abstract: A CsI salt‐based cathode which is capable of producing a modest perveance, 10 s of A/cm2 electron beam for several microseconds pulse lengths, and has little susceptibility to diode closure has been experimentally characterized. This explosive field‐emission CsI‐coated carbon fiber cathode has operated in modest 10−5 Torr vacuums at voltages up to 160 kV, and can easily be configured to provide space‐charge‐limited solid or annular electron beams in arbitrarily large diameter configurations. The CsI cathode has demonstrated negligible closure for 2 μs pulses, and has operated for 200 shots with no degradation in cathode performance. Data on the operating performance of this salt cathode, including effective gap time history and streak photographs demonstrating uniformity of the current density, are presented. A comparison of CsI cathode performance with a velvet explosive field emitting cathode used in electron‐beam production is also presented.

Light emitting diode-based nanosecond ultraviolet light source for fluorescence lifetime measurements

Abstract: A compact pulsed‐light source is devised from an InGaN/AlGaN double heterostructure light‐emitting diode (LED). The LED emits a 450‐nm (blue) light under conventional dc operation below 30 mA. When a current larger than 50 mA is applied, the intensity of the 450‐nm light saturates, but that of the 380‐nm light due to the InGaN component continues to increase. This phenomenon is utilized to realize a nanosecond ultraviolet (UV) light source. Under repetitive, large current pulsing (frequency=10 kHz, pulse width=4 ns, peak current=2 A), the peak LED emission shifts from 450 to 380 nm. Intense light pulses (peak value=40 mW) of 4‐ns duration were generated. To evaluate the potential of the pulsed LED as an excitation source, the fluorescence lifetime of a quinine‐sulfate solution was measured. The observed lifetime characteristics agreed well with the generally accepted behavior.

An improved full-bridge zero-voltage switching PWM converter using a two-inductor rectifier

Abstract: An improved full-bridge ZVS PWM using a two- inductor rectifier dc/dc converter is presented in this paper. For this improved topology, the main devices are switched on under zero-voltage (ZVS) conditions using the energy stored in the secondary filter inductors. In addition, it utilizes the low leakage inductance of a coaxial winding transformer to reset the currents in the rectifier diodes and eliminate the secondary voltage spike. The two-inductor rectifier has only one diode conduction drop in addition to frequency doubling in the output capacitor. The secondary filter size in the proposed topology is rather small. The advantages of the new topology include a wide load range with ZVS, no lost duty cycle due to diode recovery, no secondary voltage spikes, in addition to high power density and high efficiency

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.