Showing papers on "Diode published in 1990"

Light therapy system

Abstract: A light therapy system utilizes an array of light emitting diodes which emit noncoherent light in a narrow bandwidth centered at a designated wave length. The diodes are mounted to project and focus their output on a dermal zone of a patient. A continuous or a pulsed voltage differential is utilized to energize the diodes. Higher voltage differential and peak current flow across the diodes is provided in pulsed operation than in continuous operation. With a designated wave length in the infra red bandwidth, a treatment regimen including a session of 5-10 minutes of continuous operation and a session of 5-10 minutes of pulsed operation once or twice per day has been effective in alleviating various musculoskeletal disorders. A similar treatment regimen utilizing diodes emitting light centered at the red light wave length has proven effective in the treatment of skin ulcers and delayed post operative wound healing.

Optical control of microwave semiconductor devices

Abstract: The use of optically controlled devices to perform a range of circuit functions is reviewed. The optical control of amplifier performance is discussed. The optical control of two- and three-terminal oscillators and optically pumped mixers is discussed. Among the active devices treated are Gunn and IMPATT oscillators; MESFET and HEMT amplifiers, oscillators, and mixtures; and diode mixers. Future directions for research in this area are discussed. >

Temperature dependence of I-V and C-V characteristics of Ni/n-CdF2 Schottky barrier type diodes

Abstract: Current-voltage (I-V) and capacitance-voltage (C-V) measurements were performed in the temperature range 45–330 K on Ni/n-CdF2 Schottky barrier type diodes fabricated on unpolished CdF2 surface, etched with 1 : HCl. The diodes showed an MIS structure with interface states and deep donor bulk defects. Under forward bias and for T ⩾ 280 K, the electric current transport was controlled by the thermionic emission process. However, for T ⩽ 280 K, the current was controlled by thermionic field emission. The zero bias and zero temperature barrier height, φ0 = (0.67 ± 0.07) V was obtained from the I-V measurements and agreed very well with the value of φ0 = (0.60 ± 0.06) V, determined from the C-V data. The energy density of interface states estimated from the room temperature I-V measurements was ≈ 1012 cm−2 eV−1. The interface states were responsible for the non-ideal behavior of the forward I-V characteristics of the diodes. However, the non-linearity in the C−2vsV curves under reverse bias was introduced by the deep donor levels. From the C-V measurements under reverse bias, two deep levels with energies of EC - (0.7 ± 0.1) eV and EC - (1.0 ± 0.1) eV were detected.

Generation of 41 mW of blue radiation by frequency doubling of a GaAlAs diode laser

Abstract: A monolithic ring resonator of KNbO3 was used for efficient frequency doubling of a 856 nm GaAlAs diode laser. A special electronic servo technique was devised to lock the diode laser frequency to the KNbO3 cavity so that stable generation of blue output was obtained. With 105 mW of incident near‐infrared power, 41 mW of 428 nm radiation were produced. The conversion efficiency from electrical input power into the diode laser to blue output was ∼10%.

Temperature dependence of the electrical characteristics of Yb/p-InP tunnel metal-insulator-semiconductor junctions

Abstract: High barrier Yb/p‐InP metal‐insulator‐semiconductor (MIS) and metal‐semiconductor (MS) junctions were fabricated by evaporation of Yb on InP:Zn substrates. The capacitance‐voltage (C‐V) and current‐voltage (I‐V) characteristics of these devices were measured over a wide range of temperatures. From the room‐temperature forward I‐V data, the values of 1.06 and 1.30 for the ideality factor (n) were obtained for the MIS and MS diodes, respectively. The higher value of n was attributed to an order of magnitude higher density of interface states in the MS junction than in the MIS diodes. The I‐V/T data over the temperature range 190–400 K, indicated that the forward current transport in the Yb/p‐InP MIS junction was controlled by the thermionic‐field emission (TFE) mechanism. The analysis of the reverse saturation current I0 in terms of the TFE model provided a value of 1.07±0.03 V for the zero bias, zero temperature barrier height (φ0) which was in close agreement with the value of φ0=1.03±0.04 V, provided by ...

Focusing of diode laser beams: a simple mathematical model.

Abstract: A simplified mathematical model for the far field of a monomode diode laser is employed for easy but fairly accurate computations of the optical field in the focal region. The present treatment is concerned with laser junctions significantly narrower than the wavelength. The field distribution in the plane perpendicular to the diode junction is considered in detail. The results of computations are shown to agree well with the measurements. Hence, the computational code is valuable for the designing of optical devices, such as diode-fiber couplings and laser Doppler anemometers. The present work is not concerned with design calculations for specific applications. Instead, it is intended to illustrate the general features of the proposed mathematical model of monomode diode laser beams.

Submilliamp threshold vertical‐cavity laser diodes

Abstract: We report for the first time room‐temperature, continuous‐wave operation of individual vertical‐cavity laser diodes with submilliampere threshold currents. A single quantum well active region emitting at 979 nm surrounded by GaAs/AlAs Bragg reflector mirrors was used. Threshold currents were as low as 0.7 mA. A record low linewidth‐power product of 5 MHz mW and a linewidth as narrow as 85 MHz was measured. High yield and good uniformity were demonstrated.

High efficiency submillimeter frequency multipliers

Abstract: Solid-state sources have been developed for 330 and 500 GHz using cascaded varactor multipliers driven by a Gunn oscillator. The 330-GHz source uses a cascade of two balanced doublers, achieving very high efficiency, and produces an output of 4 mW. The 500-GHz source uses a cascade of a balanced doubler and single diode tripler and produces 0.7 mW. The doubler output at 330 GHz has been used to drive a harmonic mixer at 660 GHz, and plans are to drive yet another doubler at 660 GHz, where an output of 0.1-0.2 mW is expected. The output may prove to be enough LO for a cooled Schottky diode mixer. The tripled power at 500 GHz is quite sufficient for operation of Schottky diode mixers at this frequency and should be adequate as a pump source for a low-power doubler at 1 THz, such as would be used with a superconductor-insulator-superconductor (SIS) mixer. >

Characterization of p‐type ZnSe

Abstract: Lithium‐doped ZnSe has been grown on (100) GaAs by molecular beam epitaxy. The epitaxial layers are p‐type with net acceptor concentrations (NA−ND) as high as 8×1016 cm−3— the highest ever reported for molecular beam epitaxial ZnSe. Room temperature ac measurements show resistivities as low as 2.9 Ω cm. Higher Li concentrations give rise to self‐compensation and a decrease in NA−ND. The details of the electrical and optical characterization of these layers are presented. Rudimentary blue light emitting pn junction diodes have been fabricated. While these devices show dominant blue emission (463 nm) at room temperature, large turn‐on voltages indicate that the p‐ZnSe/p‐GaAs interface presents a large barrier to hole transport. Moreover, we find that difficulty in making device‐quality ohmic contacts to p‐ZnSe is the next major obstacle to the fabrication of efficient blue light emitting diodes.

A novel passive waveshaping method for single-phase diode rectifiers

Abstract: A novel passive waveshaping method for single-phase diode rectifiers is presented. It is shown that application of the proposed method maintains high-input power factor, lowers rectifier current stresses, and lowers the volt-ampere (VA) rating of the associated reactive components as compared to the standard diode rectifier. Relevant input and output current waveforms, component ratings, and power factor values are derived. Different modes of operation are discussed as a means of obtaining high performance. Key predictions, such as input/output waveforms and associated harmonic spectra, have been verified experimentally on a 1 kVA laboratory prototype unit. >

Analysis of class E zero-voltage-switching rectifier

Abstract: Analysis of Class E rectifiers offer a novel means of high-frequency high-efficiency rectification. An analysis and experimental results are presented for a class E zero-voltage-switching (lowdv/dt) rectifier. The circuit consists of a diode, a capacitor shunting the diode, and a second-order low-pass output filter. The shunt capacitor shapes the voltage across the diode so that the diode turns on and off at low dv/dt. Therefore, switching losses and switching noise are reduced significantly. An advantage of the rectifier is that the diode junction capacitance is absorbed into the shunt capacitor. The basic equations governing rectifier operation are derived. The following performance parameters are determined: current and voltage waveforms, device stresses, component values, and power-output capability. The measured performance shows excellent agreement with the design calculations. >

ZnSe light‐emitting diodes

Abstract: We report the successful fabrication of ZnSe p‐n junction light‐emitting diodes in which Li and Cl are used as p‐type and n‐type dopants, respectively.

Power and stability limitations of resonant tunneling diodes

Abstract: Stability criteria for resonant tunneling diodes are investigated. Details of how extrinsic elements, such as series inductance and parallel capacitance, affect the stability are presented. A GaAs/AlAs/InGaAs/AlAs/GaAs double-barrier diode is investigated, showing the effect of different modes of low-frequency oscillation and the extrinsic circuit required for stabilization. The effect of device stabilization on high-frequency power generation is described. The main conclusions of the paper are: (1) stable resonant tunneling diode operation is difficult to obtain, and (2) the circuit and device conditions required for stable operation greatly reduce the amount of power that can be produced by these devices. >

Influence of barrier inhomogeneities on noise at Schottky contacts

Abstract: Electronic properties of Schottky diodes depend sensitively on spatial inhomogeneities of the metal/semiconductor interface. We find that, contrary to previous theories for low‐frequency noise, the electronic properties of Schottky contacts cannot be understood if one neglects spatial fluctuations of the Schottky barrier height. Our systematic investigation of several silicide/silicon diodes yields as an empirical law that excess noise increases drastically when the standard deviation σs of the spatial distribution of Schottky barrier heights exceeds the critical threshold value of 2kT.

Repetitive flash x‐ray generator utilizing a simple diode with a new type of energy‐selective function

Abstract: The construction and the fundamental studies of a repetitive flash x‐ray generator having a simple diode with an energy‐selective function are described. This generator consisted of the following components: a constant high‐voltage power supply, a high‐voltage pulser, a repetitive high‐energy impulse switching system, a turbo molecular pump, and a flash x‐ray tube. The circuit of this pulser employed a modified two‐stage surge Marx generator with a capacity during main discharge of 425pF. The x‐ray tube was of the demountable‐diode type which was connected to the turbo molecular pump and consisted of the following major devices: a rod‐shaped anode tip made of tungsten, a disk cathode made of graphite, an aluminum filter, and a tube body made of glass. Two condensers inside of the pulser were charged from 40 to 60 kV, and the output voltage was about 1.9 times the charging voltage. The peak tube voltage was primarily determined by the anode‐cathode (A‐C) space, and the peak tube current was less than 0.6 kA. The peak tube voltage slightly increased when the charging voltage was increased, but the amount of change rate was small. Thus, the maximum photon energy could be easily controlled by varying the A‐C space. The pulse width ranged from 40 to 100 ns, and the x‐ray intensity was less than 1.0 μC/kg at 0.3 m per pulse. The repetitive frequency was less than 50 Hz, and the effective focal spot size was determined by the diameter of the anode tip and ranged from 0.5 to 3.0 mm in diameter.

Method for mirror passivation of semiconductor laser diodes

Abstract: A method for passivating mirrors in the process of fabricating semiconductor laser diodes is disclosed. Key steps of the method are: (1) providing a contamination-free mirror facet, followed by (2) an in-situ application of a continuous, insulating (or low conductive) passivation layer. This layer is formed with material that acts as a diffusion barrier for impurities capable of reacting with the semiconductor but which does not itself react with the mirror surface. The contamination-free mirror surface is obtained by cleaving in a contamination-free environment, or by cleaving in air, followed by mirror etching, and subsequent mirror surface cleaning. The passivation layer consists of Si, Ge or Sb.

33 ps optical switching of symmetric self‐electro‐optic effect devices

Abstract: We describe a new method of operation of symmetric self‐electro‐optic effect devices (S‐SEEDs) using excitation pulses shorter than the diode sweep out times. We shall call this dynamic SEED switching. Previous SEEDs are optically bistable logic devices which use the unique properties of multiple quantum well structures placed in the intrinsic i regions of two p‐i‐n diodes reverse biased in series. Conventional operation of S‐SEEDs is at the exciton wavelength where absorption decreases with increasing electric field. Utilizing the dynamic properties of the S‐SEED we demonstrate that switching is possible at any wavelength where there is a nonlinear response showing a threshold. The major advantages of dynamic over conventional operation, is that it can be faster while requiring less optical energy, is automatically reset each cycle, and is less susceptible to saturation.

Monolithically integrated power MOSFET and Schottky diode with improved reverse recovery characteristics

Abstract: A power DMOSFET structure with a monolithically integrated Schottky diode located under the source contact pad is described. In this structure the source contact metallization step is also used to fabricate an epitaxial drift region Schottky diode in parallel with the parasitic body p-n junction diode of the power MOSFET. Such a structure results in significantly improved internal diode switching characteristics with no degradation in the on-state resistance and drain-source breakdown voltage. The integral power MOSFET technology was used to fabricate 30- and 45-V vertical power DMOSFETs with a reduction in peak reverse current and stored charge of more than 25% as compared to a conventional power DMOSFET. The Schottky diode consumed less than 15% of the active transistor area. >

A 2 kbit array of symmetric self-electrooptic effect devices

Abstract: A 64*32 array of symmetric self-electrooptic effect devices, each of which can be operated as a memory element or logic gate, is discussed. The required optical switching energies of the devices were approximately 800 fJ and approximately 2.5 pJ at 6 and 15 V bias, respectively, and the fastest switching time measured was approximately 1 ns. Either state of the devices could be held with continuous or pulsed incident optical signals with an average optical incident power per input beam of approximately 200 nW or less than 1 mW for the entire array. Photocurrent and reflectivity were measured for all 2048 devices. Only one device failed to have the negative resistance required for bistability, and only nine of the devices fell outside a band of +or-20% of the mean. Additionally, over 200 devices in the array were operated in parallel using low-power semiconductor laser diodes. >

Electronic properties of junctions between silicon and organic conducting polymers

Abstract: Diodes formed from semiconductor/metal interfaces often display non-ideal electronic properties. For instance, silicon/metal (Schottky) diodes made from n-type silicon and a variety of contacting metals exhibit only small differences in their rectification properties, despite theoretical and practical expectations that changes in the metal should effect changes in device properties. Similarly, Schottky diodes formed on p-type silicon generally exhibit ohmic behaviour with poor rectification characteristics. This lack of electrical response to changes in the properties of the contacting metal phase is generally attributed to interfacial reactions that take place during the high-temperature thermal or electron-beam deposition of metals onto silicon. Here we describe the fabrication of diodes using a low-temperature chemical procedure, in which contact to the semiconductor is made by a layer of the conducting organic polymer, polyacetylene. Unlike conventional metals, the electrical properties of polyacetylene can be manipulated through choice of the polymer dopant. The resultant organic/inorganic interfaces behave more ideally than contacts with conventional metals, in that changes in the electrical properties of the conducting polymer exert a large and predictable effect on the electrical properties of the resulting semiconductor/polymer diodes.

Semiconductor device physics of conjugated polymers

Abstract: Conjugated polymers which can be processed to form thin, coherent films can be used as the active layers in semiconductor device structures. We have used the Durham precursor route to polyacetylene to fabricate a range of unipolar devices including Schottky barrier diodes, MIS diodes and MISFET’s. Although carrier mobilities are low, limited by thermally-activated transport between chains, these devices work well, and we find that these structures are remarkably free of surface states and bulk defect states with energy levels within the gap. The fundamental excitation of the trans-polyacetylene chain is the self-localised soliton-like kink defect in the bond alternation pattern along the chain; the soliton has associated with it an energy state at mid-gap of non-bonding pz character. We have been particularly concerned to demonstrate the formation of solitons from charges injected into the polyacetylene layer in these device structures, and have measured the changes in the optical properties that accompany soliton formation. For the MIS structures working in accumulation mode we find the ‘mid-gap’ transition from soliton level to the band edge at energies ranging between 0.55 eV (characteristic of the bulk) for polyacetylene on polymeric insulator layers to 0.8 eV when formed on silicon dioxide. We discuss this spread in energies in terms of the different surface structures at these different interfaces. We also show data for the characteristic vibrational excitations of the soliton, including both the IR-active translation modes and the Raman active amplitude modes.

Anomalous inductive effect in selenium Schottky diodes

Abstract: A region of anomalous negative capacitance has been observed with forward bias in Se‐Tl Schottky evaporated layer structures. The effect, which is more prevalent in diodes with lower series resistance, is due to an inductive contribution to the impedance that is believed to arise from high‐level injection of minority electrons into the bulk selenium.

Instrumentation for the stable operation of laser diodes

Abstract: We have developed a constant current supply and a temperature control circuit that can be used for frequency‐stable operation of laser diodes. These instruments can stabilize laser diode injection current and temperature to better than ±1 μA and ±0.3 mK, respectively, over time periods exceeding 1 h. We have excited the Li(2S↔2P) transition with a red‐light‐emitting laser diode and find that our instrumentation stabilizes the laser frequency to within ±10 MHz over a period exceeding 1 h.

Method and apparatus for increasing the high frequency sensitivity response of a sampler frequency converter

Abstract: A method and apparatus comprising a sampler frequency converter having a first and a second diode. A local oscillator having a frequency F LO , a step recovery diode and a balun transformer are used for providing positive and negative sampling pulses to the diodes for sampling an input signal applied to the diodes having a frequency F IN . An output signal is provided by the diodes having a frequency F OUT which is defined by the relationship F OUT |F IN ±N×F LO | where N is an integer harmonic number 1, 2, 3 . . . and the output signal has an amplitude which varies as a function of (sin x)/x where x=F IN . A bandpass filter is provided which is responsive to the output signal for filtering a predetermined band of frequencies therefrom and a bias circuit is provided for forward biasing the diodes so that the frequency F IN of said input signal at which nulls occur in said (sin x)/x relationship occur at a lower frequency after said biasing than before said biasing.

Rod laser with optical pumping from a source having a narrow emitting area

Abstract: An Nd/YAG slab laser (1) is pumped by laser diodes (2) placed at a distance from the laser slab. Reflectors (7) convey the light from the diodes to the slab. The distance is such that the density of such light is made uniform. A cooling fluid flows along a compartment (5) between the diodes and the slab. The invention is applicable to producing infrared coherent light.

Flat doping profile double-drift silicon IMPATT for reliable CW high-power high-efficiency generation in the 94-GHz window

Abstract: The main results of a theoretical and experimental study of the optimization of flat doping profile double-drift silicon IMPATT diodes for the realization of reliable CW high-power high-efficiency solid-state oscillators operating in the 94 GHz atmospheric propagation window are presented. This study has been carried out by means of an IMPATT oscillator model which takes into account the thermal limitation, bias effect, and diode impedance matching. It relies on an accurate p-n junction device drift-diffusion model that includes the heavily doped regions of the collectors. This model has been used to quantify the influence of the various parameters determining the oscillator RF output performance. An explanation of the interesting noise performance of these millimeter-wave IMPATT diodes is proposed. >

Input protection circuit for CMOS devices

Abstract: An input protection circuit protects MOS semiconductor circuits from electrostatic discharge voltages and from developing circuit latchup. The input protection circuit includes a low resistance input resistor, and two complementary true gated diodes. One true gated diode has a P-doped node coupled to the input node, and a gate and N-doped node coupled to a high voltage power supply node. The other true gated diode has a N-doped node coupled to the input node, and a gate and P-doped node coupled to a second power supply node.

Non-equilibrium modes of operation of narrow-gap semiconductor devices

Abstract: Research work is reviewed which uses the phenomena of minority carrier extraction and minority carrier exclusion to reduce the carrier densities in narrow-gap Hg1-xCdxTe alloys to near-extrinsic values at temperatures where the materials are normally intrinsic. This is of particular interest for the suppression of Auger noise which otherwise severely limits the performance achievable from infrared detectors at near-ambient operating temperatures. Improved performance has been obtained from excluding photoconductive detectors at modulation frequencies above 10 kHz. Theoretical work predicts improved performance from heterojunction extracting diodes. Early experiments on 'proximity-extracting' diode structures show large reductions in leakage current at intermediate and ambient temperatures compared to non-extracted diodes, but the residual current is higher than that predicted from Shockley-Read generation. Bipolar transistor action is observed at temperatures where the material is near-intrinsic in equilibrium. The transistor characteristics are strongly influenced by electron impact ionisation.

A broad-area mode-coupling model for multiple-stripe semiconductor lasers

Abstract: An analytical perturbation model is presented for calculating the eigenmodes of multistripe diode laser arrays. In contrast to the supermode theory, the array modes are developed into a linear combination of broad-area modes instead of individual waveguide modes. Two perturbations from which mode coupling originates are taken into account, namely the periodic gain and index grating formed by the current stripes and the effect of temperature variations across the junction. Results for the model are shown to be in excellent agreement with the experimental data, particularly concerning the details of the far-field structure of free-running diode arrays. The model provides a new physical interpretation of the coupling of modes due to temperature variations across the array width. >