Showing papers on "Diode published in 1993"

Power Electronics: Circuits, Devices and Applications

Abstract: 1. Introduction. 2. Power Semiconductor Diodes and Circuits. 3. Diode Rectifiers. 4. Power Transistors. 5. DC-DC Converters. 6. Pulse-width Modulated Inverters. 7. Thyristors. 8. Resonant Pulse Inverters. 9. Multilevel Inverters. 10. Controlled Rectifiers. 11. AC Voltage Controllers. 12. Static Switches. 13. Flexible AC Transmission Systems. 14. Power Supplies. 15. DC Drives. 16. AC Drives. 17. Gate Drive Circuits. 18. Protection of Devices and Circuits. Appendices: Three-phase Circuits, Magnetic Circuits, Switching Functions of Converters, DC Transient Analysis, Fourier Analysis, Thyristor Commutation Techniques, Data Sheets.

Efficient light-emitting diodes based on polymers with high electron affinities

Abstract: CONJUGATED polymers have been incorporated as active materials into several kinds of electronic device, such as diodes, transistors1 and light-emitting diodes2. The first polymer light-emitting diodes were based on poly(p-phenylene vinylene) (PPV), which is robust and has a readily processible precursor polymer. Electroluminescence in this material is achieved by injection of electrons into the conduction band and holes into the valence band, which capture one another with emission of visible radiation. Efficient injection of electrons has previously required the use of metal electrodes with low work functions, primarily calcium; but this reactive metal presents problems for device stability. Here we report the fabrication of electroluminescent devices using a new family of processible poly(cyanoterephthalylidene)s. As the lowest unoccupied orbitals of these polymers (from which the conduction band is formed) lie at lower energies than those of PPV, electrodes made from stable metals such as aluminium can be used for electron injection. For hole injection, we use indium tin oxide coated with a PPV layer; this helps to localize charge at the interface between the PPV and the new polymer, increasing the efficiency of recombination. In this way, we are able to achieve high internal efficiencies (photons emitted per electrons injected) of up to 4% in these devices.

Semiconducting polymer‐buckminsterfullerene heterojunctions: Diodes, photodiodes, and photovoltaic cells

Abstract: The characterization of rectifying heterojunctions (diodes) fabricated from a semiconducting polymer, a soluble derivative of poly(phenylene‐vinylene), and buckminsterfullerene, C60, are reported. Rectification ratios in the current versus voltage characteristics exceed 104. When illuminated, the devices exhibit a large photoresponse as a result of photoinduced electron transfer across the heterojunction interface from the semiconducting polymer (donor) onto C60 (acceptor). The photodiode and photovoltaic responses are characterized. Photoinduced electron transfer across the donor‐accepted rectifying heterojunction offers potential for photodetector and for solar cell applications.

Semiconductor Optoelectronic Devices

Abstract: Elemental and compound semiconductors electronic properties of semiconductors optical processes in semiconductors junction theory light-emitting diodes lasers - operating principles lasers - structures and properties photodetectors special detection schemes solar cells opto-electronic modulation and switching devices opto-electronic integrated circuits.

High‐power InGaN/GaN double‐heterostructure violet light emitting diodes

Abstract: InGaN/GaN double‐heterostructure light‐emitting diodes were fabricated. The output power was 90 μW and the external quantum efficiency was as high as 0.15% at a forward current of 20 mA at room temperature. The peak wavelengths of the electroluminescence(EL) varied between 411 and 420 nm with changes in the growth temperatures of an InGaN active layer between 820 and 800 °C. The full widths at half maximum of EL were between 22 and 25 nm.

Blue light-emitting diode with degenerate junction structure

Abstract: A light emitting diode is disclosed that emits light in the blue region of the visible spectrum with increased brightness and efficiency. The light emitting diode comprises an n-type silicon carbide substrate; an n-type silicon carbide top layer; and a light emitting p-n junction structure between the n-type substrate and the n-type top layer. The p-n junction structure is formed of respective portions of n-type silicon carbide and p-type silicon carbide. The diode further includes means between the n-type top layer and the n-type substrate for coupling the n-type top layer to the light-emitting p-n junction structure while preventing n-p-n behavior between the n-type top layer, the p-type layer in the junction structure, and the n-type substrate.

Control of emission characteristics in organic thin‐film electroluminescent diodes using an optical‐microcavity structure

Abstract: An electroluminescent diode with a microcavity structure which comprised a reflective Ag anode (36 nm), a hole transport dye layer (250 nm), an emission dye laser (15 nm), an electron transport dye layer (240 nm), and a reflective MgAg cathode was fabricated. A diode without the microcavity structure with a transparent ITO anode was also prepared for reference. The diode with microcavity was driven in the electric excitation mode and emission spectra at fixed detection angles were measured together with the angular dependence of emission intensity at fixed wavelengths. A sharpening of emission spectra and a marked alteration of emission patterns in the diode with microcavity were observed.

Absorption measurements of water-vapor concentration, temperature, and line-shape parameters using a tunable InGaAsP diode laser.

Abstract: A tunable diode laser diagnostic based on spectrally resolved laser absorption has been developed to detect water vapor. The system uses a distributed feedback InGaAsP diode laser, emitting at ~ 1.38 µm. The diode laser is tuned in wavelength by modulation of the current, resulting in 1-cm(-1) tuning at 80-Hz repetition rate. The directly measured absorption spectra yield values for water-vapor concentration and temperature, as well as a collision-broadening line shape. To our knowledge, we accurately determined required data for H(2)O line strengths and self-broadening coefficients for several spectral lines in a static cell filled with pure water vapor. The temperature and concentration of the water vapor present in laboratory room air and in the postflame gases above a methane-air flat flame burner have also been measured. These results agree well with calculated values and independent measurements.

Frequency dependence of forward capacitance-voltage characteristics of Schottky barrier diodes

Abstract: The frequency dependence of forward capacitance-voltage characteristics of Schottky barrier diodes were investigated by considering the series resistance effect. It is seen that in presence of a series resistance, the capacitance-voltage plot exhibits a peak. The peak value of the capacitance is found to vary with series resistance, interface state density and the frequency of the a.c. signal. The effect of series resistance on the capacitance is found appreciable at higher frequencies when capacitance decreases rapidly with frequency. On the other hand, the conductance of the diode increases with frequency in the high frequency limit. Such a variation in conductance limits the use of well known conductance technique to determine interface state density.

Room temperature continuous operation of blue-green laser diodes

Abstract: Continuous-wave operation in wide-gap II-VI semiconductor current injection laser diodes at room temperature has been demonstrated for the first time. Stimulated emission was observed at a wavelength of 523.5 nm with a threshold current of 45 mA (1.4 kA/cm2) from ZnCdSe/ZnSe/ZnMgSSe single-quantum-well (SQW) separate-confinement heterostructure (SCH) laser diodes.

Polarized surface-emitting laser

Abstract: A vertical-cavity, surface-emitting semiconductor diode laser having a monolithic and planar surface and having lateral anisotropy in order to control the polarization of the emitted beam of light. The diode laser includes a body of a semiconductor material having an active region therein which is adapted to generate radiation and emit the radiation from a surface of the body, and a separate reflecting mirror at opposite sides of the active region with at least one of the mirrors being partially transparent to the generated light to allow the light generated in the active region to be emitted therethrough. The anisotropy may be provided by utilizing anisotropy in the atomic or molecular structure of the materials forming the laser, or by anisotropic patterning or deliberate offset alignment in processing of the laser or through anisotropic structures in the laser cavity to control the polarization of the emitted beam.

Integrated solid state light emitting and detecting array and apparatus employing said array.

Abstract: There is provided an integrated semiconductor source-detector matrix (10) in which solid state photonic diodes (12a-12i) are configured as LEDs, disposed on a substrate and coupled to electronic circuits so that the diodes can be individually driven to emit light to detect light as may be desired. Providing an integrated matrix (10) of light source and light sensor units disposed in close proximity results in each unit having nearly coextensive fields of view and illumination (157). Apparatus, such as bar code and optical readers utilizing such a matrix are shown, and are insensitive to the diffusion and laminate effects. In alternate embodiments the matrix (10) is coupled to remote sensors (94) or another similar matrix to provide optical communication and interchange devices having high bandwidth.

A High Efficiency Diode-Pumped Nd:YVO 4 Slab Laser

Abstract: Optical-to-optical conversion efficiencies of as high as 32% with a slope efficiency of 44% were obtained with a novel diode-bar, side-pumped laser cavity design. A slab geometry with a single, high-angle-of-incidence reflection was used to extract gain from near the pump face of a Nd:YVO(4) bar that absorbed strongly at the pump wavelength. Small-signal gains of greater than 8 cm(-1) and pulse energies of as much as 3.2 mJ were obtained in an almost TEM(00) mode. Aperturing effects by the laser rod were found to limit the effects of nonuniform gain on the laser mode.

Silicon carbide UV photodiodes

Abstract: SiC photodiodes were fabricated using 6 H single-crystal wafers. These devices have excellent UV responsivity characteristics and very low dark current even at elevated temperatures. The reproducibility is excellent and the characteristics agree with theoretical calculations for different device designs. The advantages of these diodes are that they will operate at high temperatures and are responsive between 200 and 400 nm and not responsive to longer wavelengths because of the wide 3-eV bandgap. The responsivity at 270 nm is between 70% and 85%. Dark-current levels have been measured as a function of temperature that are orders of magnitude below those previously reported. Thus, these diodes can be expected to have excellent performance characteristics for detection of low light level UV even at elevated temperatures. >

A low‐noise high‐speed diode laser current controller

Abstract: We describe a new diode laser current controller which features low current noise, excellent dc stability, and the capacity for high‐speed modulation. While it is simple and inexpensive to construct, the controller compares favorably with the best presently available commercial diode laser current controllers.

Measuring device e.g. water or moisture sensor

Abstract: The measurement arrangement has a light emitting diode (10) whose emitted radiation is fed into a plate or wall (11) which is transmissive for a defined wavelength, esp. a reflection path (11a). The light is coupled directly into the wall or plate from the diode. The surface (10a) of the diode facing the wall or plate is matched to the surface shape of the wall or plate. The light emitting diode is a commercially available type with a bright chip whose surface is cut to match that of the wall or plate. The light is coupled into the wall or plate as a beam and at an angle of incidence which essentially differs from a normal to the plate or wall by more than the refraction angle of total reflection.

Synthesized source for white-light sensing systems.

Abstract: We report a novel technique in which by combining the output from two multimode laser diodes a synthesized source with an extremely short coherence length is produced for use in white-light interferometric sensing systems. Experimentally and theoretically it is demonstrated that, by summing the autocorrelation function of two multimode laser diodes with a wavelength difference of 108 nm, a synthesized source with an equivalent coherence length of ~4 μm is generated, greatly reducing the signal-to-noise ratio required to identify the central fringe position.

Visible electroluminescence from porous silicon diodes with an electropolymerized contact

Abstract: An electrochemical technique is proposed to form a solid‐state electrical contact of porous Si (PS) electroluminescence (EL) diodes. The PS layers were created by anodizing nondegenerate p‐type single‐crystal Si wafers in an HF solution, and then electrochemically polymerizing semitransparent conducting polypyrrole films into the PS layer. The current‐voltage characteristics and the voltage and current dependence of the EL intensity were significantly improved in comparison with our experimental PS‐EL diode with a thin Au film contact. Our result suggests that the electrode impregnation into PS is very useful for an efficient and stable EL operation.

Diode-pumped microchip Er-Yb:glass laser.

Abstract: A single-frequency, diode-pumped, Er-Yb:glass microchip laser at a 1530-nm wavelength has been designed and operated. An output power of greater than 25 mW, a linewidth narrower than 1 kHz, and a slope efficiency of 22% have been obtained.

Unidirectional operation in a semiconductor ring diode laser

Abstract: We report the first demonstration of a unidirectional ring diode laser based on the use of an active crossover waveguide. The crossover waveguide introduces both a nonreciprocal loss and gain into the ring cavity to promote unidirectional lasing in the clockwise ring direction. Up to 95% of the continuous‐wave lasing output of 3.5 mW (at 150 mA ring current) is emitted from this preferred lasing direction. Unidirectional operation of the ring diode laser is also shown to increase the linearity of the light‐vs‐current curves, eliminating kinks otherwise occurring from gain competition in the ring cavity.

Implantable cardioversion-defibrillation patch electrodes having means for passive multiplexing of discharge pulses

Abstract: An apparatus for treating arrhythmias of the human heart includes a defibrillator, and an arrangement for providing passive diode multiplexing between two patches for bidirectionally passing an electric current through a human heart. The arrangement is formed by connecting a cathode of a first diode to a first mesh electrode on a first conductor and connecting an anode of a second diode to a second mesh electrode on the first patch. An anode of the first diode and a cathode of the second diode are then connected to a lead. An identical diode arrangement is provided for the second patch.

Continuous-wave operation of 489.9nm blue laser diode at room temperature

Abstract: At room temperature (296 K), continuous-wave (CW) operation of a blue laser diode has been achieved. The emission wavelength is 489.9 nm, and the threshold current and voltage is 93 mA (1.5 kA/cm2) and 6.3 V, respectively. The laser consists of a ZnCdSe/ZnSSe/ZnMgSSe single-quantum-well (SQW) separate-confinement heterostructure (SCH).

High single-transverse-mode output from external-cavity surface-emitting laser diodes

Abstract: Room‐temperature cw electrically pumped external‐cavity surface‐emitting laser diodes are reported. The external cavity provides a way to control the transverse modes of the surface‐emitting laser diodes. Powers greater than 100 mW pulsed and 2.4 mW cw in the lowest order (TEM00) transverse mode are reported. The surface‐emitting laser diode was grown on a p‐doped substrate, resulting in uniform current injection in devices as large as 100 μm in diameter. To our knowledge, this is also the first report of a working surface‐emitting laser diode grown on a p‐type substrate.

Quasi-resonant diode drive current source

Abstract: A quasi-resonant diode drive current source provides high power pulsed current that drives light emitting diodes, and the like. The pulsed output current of the quasi-resonant diode drive current source is sensed, and is regulated by a control loop to a level required by the light emitting diodes. In a specific embodiment of the invention, a zero-current-switched full wave quasi-resonant buck converter is described that provides a high amplitude pulsed output current required to drive light emitting pump diodes used in a solid state diode pumped laser. The use of a quasi-resonant converter as a pulsed current source provides a much higher conversion efficiency than conventional laser current sources. This higher efficiency results in less input power drawn from a power source and cooler operation, resulting in a higher reliability current source.

A broadband, planar, doubly balanced monolithic Ka-band diode mixer

Abstract: A planar monolithic diode mixer that achieves 5-10-dB conversion loss and very low distortion and spurious responses over a 26-40-GHz RF and local oscillator (LO) bandwidth and DC-12-GHz IF is described. Two types of diodes have been used: the first used the gate-to-channel junctions of 0.2- mu m*80- mu m InGaAs HEMTs; and the second used Schottky diodes realized in HBT technology. The baluns are Marchand-like coplanar structures. >

Low-threshold buried-ridge II-VI laser diodes

Abstract: Blue‐green (λ=511 nm) separate confinement laser structures based on lattice‐matched MgZnSSe‐ZnSSe‐CdZnSe have been grown by molecular beam epitaxy. Wide stripe gain‐guided devices have been fabricated from several such wafers. These devices exhibit room‐temperature pulsed threshold current densities as low as 630 A/cm2 and threshold voltages less than 9 V. Using a novel self‐aligned process that results in a planar surface, buried‐ridge laser diodes have also been fabricated. These devices have demonstrated room‐temperature threshold currents as low as 2.5 mA, which is more than a factor of 50 lower than that of any previously reported II‐VI laser diode. Room‐temperature operation at duty factors up to 50% has been demonstrated. The far‐field patterns from these devices indicate single lateral mode operation, suitable for diffraction‐limited applications, such as optical data storage.

Self-heating effects in basic semiconductor structures

Abstract: Investigates the effects of self-heating on the high current I-V characteristics of semiconductor structures using a fully coupled electrothermal device simulator. It is shown that the breakdown in both resistors and diodes is caused by conductivity modulation due to minority carrier generation. In isothermal simulations with T=300 K, avalanche generation is the source of minority carriers. In simulations with self-heating, both avalanche and thermal generation of minority carriers can contribute to the breakdown mechanism. The voltage and current at breakdown are dependent on the structure of the device and the doping concentration in the region with lower doping. For all structures, except highly doped resistors with poor heating sinking at the contacts, the temperature at thermal breakdown ranged from 1.25T/sub i/ to 3T/sub i/, where T/sub i/ is the temperature at which the semiconductor goes intrinsic. Hence, it is found that T=T/sub i/ is not a general condition for thermal (or second) breakdown. From these studies, an improved condition for thermal breakdown is proposed. >

Modeling and design of proton-implanted ultralow-threshold vertical-cavity laser diodes

Abstract: Detailed theoretical models are presented and used for investigating the optical, electrical, and thermal characteristics of gain-guided vertical-cavity lasers. A two-dimensional description of current flow in the proton-implanted region is achieved. Heterojunctions are taken into account for the first time, and their influence on current spreading is demonstrated. Thorough finite-element calculations of the temperature profile in the whole device indicate the formation of a thermally induced waveguide. The temperature dependence of threshold current is evaluated, and it is shown that different mode positions greatly influence the output characteristics of the laser. The models are used to analyze the behavior of three-terminal vertical-cavity lasers. Good agreement is obtained between experimental and theoretical results. Using optimized design, record low threshold currents of 650 mu A have been achieved. >

Low bandgap photovoltaic cell with inherent bypass diode

Abstract: A photovoltaic (PV) cell with a single pn-junction is disclosed that is capable of functioning as both a current source and a bypass diode. The photovoltaic cell is made of material that has a low bandgap energy, 1.0 eV, or less. One version of the PV cell is formed of a GaSb wafer doped with Te to form an n-region; the Te concentration is between 6 and 10×1017 atoms/cm3. Multiple PV cells of this invention can be connected in series or in parallel or in tandem in a primary-booster tandem pair to form a circuit without the requirement of protecting the individual cells of the circuit with a separate bypass diode.