Showing papers on "Diode published in 1989"

Self-consistent study of the resonant-tunneling diode

Abstract: Quantum transport in the resonant-tunneling diode (RTD) is modeled here with the Wigner formalism including self-consistent potentials for the first time. We examine the computational aspects of the Wigner-function approach and the boundary conditions for the model. The calculated I-V characteristics show an intrinsic bistability in the negative-differential-conductivity region of the curve. Intrinsic bistability results from charge storage and the subsequent shifting of the internal potential of the device. The cathode region of the RTD shows a strong depletion and quantization of electrons in a deep triangular potential well, which reduces the barrier height to a ballistic electron injected from the cathode, enhancing the valley current and reducing the peak-to-valley ratio. Undoped spacer layers prevent the formation of a deep quantum well at the cathode barrier, and the distribution does not deplete as sharply as without the spacer layer. The I-V curve with the spacer layers shows a much lower negative resistance, and a sharper bistable region. A finite relaxation time for the electrons increases the negative resistance, reduces the peak-to-valley ratio of the current, and causes a ``soft'' hysteresis in the bistable region. A zero-bias anomaly is found to result from high-momentum tails in the distribution at the barrier interface. These high-momentum tails contribute a small high-conductance current. The transient current during switching from the peak to the valley of the I-V curve shows inductive behavior and negative resistance for frequencies below 2 THz.

Blue light emitting diode formed in silicon carbide

Abstract: The present invention comprises a light emitting diode formed in silicon carbide and that emits visible light having a wavelength of between about 465-470 nanometers, or between about 455-460 nanometers, or between about 424-428 nanometers. The diode comprises a substrate of alpha silicon carbide having a first conductivity type and a first epitaxial layer of alpha silicon carbide upon the substrate having the same conductivity type as the substrate. A second epitaxial layer of alpha silicon carbide is upon the first epitaxial layer, has the opposite conductivity type from the first layer, and forms a p-n junction with the first epitaxial layer. In preferred embodiments, the first and second epitaxial layers have carrier concentrations sufficiently different from one another so that the amount of hole current and electron current that flow across the junction under biased conditions are different from one another and so that the majority of recombination events takes place in the desired epitaxial layer.

Method of production of light emitting diodes

Abstract: The invention is a method for preparing a plurality of light emitting diodes on a single substrate of a semiconductor material. The method is used for structures where the substrate includes an epitaxial layer of the same semiconductor material that in turn comprises layers of p-type and n-type material that define a p-n junction therebetween. The epitaxial layer and the substrate are etched in a predetermined pattern to define individual diode precursors, and deeply enough to form mesas in the epitaxial layer that delineate the p-n junctions in each diode precursor from one another. The substrate is then grooved from the side of the epitaxial layer and between the mesas to a predetermined depth to define side portions of diode precursors in the substrate while retaining enough of the substrate beneath the grooves to maintain its mechanical stability. Ohmic contacts are added to the epitaxial layer and to the substrate and a layer of insulating material is formed on the diode precursor. The insulating layer covers the portions of the epitaxial layer that are not covered by the ohmic contact, any portions of the one surface of the substrate adjacent the mesas, and the side portions of the substrate. As a result, the junction and the side portions of the substrate of each diode are insulated from electrical contact other than through the ohmic contacts. When the diodes are separated they can be conventionally mounted with the junction side down in a conductive epoxy without concern that the epoxy will short circuit the resulting diode.

Oscillations up to 420 GHz in GaAs/AlAs resonant tunneling diodes

Abstract: We report room‐temperature oscillations up to frequencies of 420 GHz in a GaAs resonant tunneling diode containing two 1.1‐nm‐thick AlAs barriers. These results are consistent with a recently proposed equivalent circuit model for these diodes in which an inductance accounts for the temporal delay associated with the quasibound‐state lifetime. They are also in accordance with a generalized impedance model, described here, that includes the effect of the transit time delay across the depletion layer. Although the peak‐to‐valley ratio of the 420 GHz diode is only 1.5:1 at room temperature, we show that its speed is limited by the parasitic series resistance rather than by the low negative conductance. A threefold reduction in this resistance, along with a comparable increase in the peak‐to‐valley ratio, should allow oscillations up to about 1 THz.

Quantum-Barrier-Varactor Diodes for High-Efficiency Millimetre-Wave Multipliers

Abstract: A new device, the quantum-barrier-varactor diode (QBV diode), is proposed for use in multipliers for millimetre waves. Since the capacitance/voltage characteristic is symmetric, only odd harmonics are obtained. Hence there is no idler circuit to consider for the tripler and only one for the quintupler. It is shown that for triplers and quintuplers, the theoretical efficiency using QBVs is comparable or possibly larger than using Schottky varactor diodes.

Enhanced mode locking of color-center lasers.

Abstract: A significant enhancement in the mode locking of a KCl:Tl color-center laser has been observed when a length of optical fiber having positive group-velocity dispersion was incorporated within an external control cavity. Pulse durations of ~260 fsec were obtained by this method, representing a compression factor ~60× that with the color-center laser alone. Similar results have also been observed with an InGaAsP semiconductor diode amplifier as the nonlinear element within the control cavity.

Double epitaxy improves single-photon avalanche diode performance

Abstract: A new single-proton avalanche diode (SPAD) with double-epitaxial silicon structure is presented. The device has a time response with short diffusion tail (270 ps time-constant), high resolution (45 ps FWHM, full-width at half maximum of the peak) and low noise, i.e. low-dark-count rate.

Resonant interband tunnel diodes

Abstract: Novel device structures are proposed, incorporating quantum wells and a pn diode structure. Such a device combines the structure and behavior of both resonant tunneling diodes and conventional tunnel diodes, leading to high speed and low excess current. There is interband tunneling between the conduction band and the valence band, as is in the case for a tunnel diode, but carriers are confined within quantum wells. Under small forward bias the diodes are expected to behave in a manner very similar to that of a tunnel diode formed of bulk material. Under large forward bias, however, the devices act much like resonant tunneling diodes, and display additional negative resistance regions.

Double heterostructure GaAs/AlGaAs thin film diode lasers on glass substrates

Abstract: The epitaxial liftoff approach has been attracting increasing interest as an alternative to lattice-mismatched heteroepitaxy. A thin-film GaAs double heterostructure injection diode laser fabricated on a glass substrate by the epitaxial liftoff technique is reported. This presages the integration of the two major optical communication materials, III-V semiconductor crystals with SiO/sub 2/ glass. >

High quantum efficiency, high power, modulation doped GaInAs strained-layer quantum well laser diodes emitting at 1.5 mu m

Abstract: Buried heterostructure Ga0.2In0.8As strained-layer (strain 1.8%) separate confinement, multiple quantum well laser diodes emitting at 1.5 μm were fabricated by hybrid LP-MOVPE/LPE. Improved performance as a result of the application of a strained-layer active region is demonstrated for the first time. A CW threshold current of 10 mA, differential quantum efficiency of 82%, T0 of 97 K and maximum output powers/facet as high as 70 mW CW and 180 mW for pulsed operation were measured. Lifetests at 60°C heat-sink temperature and 5 mW output power show almost no degradation after 2000 h.

Fabrication of detectors and transistors on high-resistivity silicon

Abstract: A new process for the fabrication of silicon p-i-n diode radiation detectors is described. The utilization of backside gettering in the fabrication process results in the actual physical removal of detrimental impurities from critical device regions. This reduces the sensitivity of detector properties to processing variables while yielding low diode reverse-leakage currents. In addition, gettering permits the use of processing temperatures compatible with integrated-circuit fabrication. P-channel MOSFETs and silicon p-i-n diodes have been fabricated simultaneously on 10 k..cap omega../center dot/cm silicon using conventional integrated-circuit processing techniques. 25 refs., 5 figs.

Coherent operation of an array of diode lasers using a spatial filter in a Talbot cavity

Abstract: Coherent operation of an array of AlGaAs diode lasers was obtained by placing the array in an external cavity which made use of the Talbot self‐imaging effect to couple the laser diodes together. A spatial filter was required to suppress oscillation of the highest order mode of the array. This filter introduced no significant loss to the cavity mode, and the mode was observed to be stable up to the maximum rated drive current for the device.

Stability and quantum efficiency performance of silicon photodiode detectors in the far ultraviolet.

Abstract: Recent improvements in silicon photodiode fabrication technology have resulted in the production of photodiodes which are stable after prolonged exposure to short wavelength radiation and which have efficiencies in the far ultraviolet close to those predicted using a value of 3.63 eV for electron-hole pair production in Si. Quantum efficiency and stability data are presented in the 6-124-eV region for several variations on the basic successful design and on devices with extremely thin silicon dioxide antireflecting/passivating layers. The results indicate that the oxide is dominant in determining many of the performance parameters and that a stable efficient far ultraviolet diode can be fabricated by careful control of the Si-SiO(2) interface quality.

432-nm source based on efficient second-harmonic generation of GaAlAs diode-laser radiation in a self-locking external resonant cavity

Abstract: Using a potassium niobate crystal in a modified self-locking power-buildup cavity, we have frequency doubled the 865-nm output from a GaAlAs laser diode. With 12.4 mW of input power we have obtained a unidirectional output of 0.215 mW at 432 nm. In contrast to previous diode doubling experiments, the output was both single frequency and circular Gaussian. With better optics, substantially higher conversion efficiencies should be possible using this technique.

Pulsed molecular-beam, diode-laser spectrometry using rapid scanning techniques

Abstract: We describe a diode‐laser spectrometer for obtaining direct absorption, rovibrational spectra of monomers and/or weakly bound, molecular complexes which are found in supersonic expansions. The spectrometer incorporates a tunable, semiconductor diode‐laser source and a pulsed‐gas slit nozzle. White cell optics are used in the vacuum chamber to increase effective path length, and a Fabry–Perot etalon is used for relative frequency calibration. Stabilization of the source output is accomplished by locking onto a zero crossing of the etalon fringe‐spacing pattern with a gated integrator. The diode laser is scanned rapidly (∼0.2 cm−1/ms) to modulate absorption signals at frequencies which can be electronically filtered from source noise. For 2000 scans, absorbances as small as 1.3×10−5 (0.003% absorption) can be detected. Amplitude fluctuations in the detected signal due to interference effects in the optics and gain variations in the diode laser are eliminated by recording data with and without gas flow from ...

Improved recovery of fast power diodes with self-adjusting p emitter efficiency

Abstract: A fast p-n-n/sup +/ power rectifier, which shows a significantly improved recovery behavior, is discussed. The p layer of this diode consists of a p/sup +/ region of high injection efficiency and a densely interspersed p region of low injection efficiency. The lateral distances are chosen in such a manner that the high efficiency of the p/sup +/ region becomes effective at high currents only, whereas, up to the normal operative forward current, the p emitter efficiency is small. By commutation, this results in a strong reduction of the peak reverse current and a significantly softer reverse current decay compared to standard diodes designed for the same blocking and forward voltages. >

Two terminal multi-band infrared radiation detector

Abstract: A radiation detector 10 includes a first heterojunction 14A and a second heterojunction 16A electrically coupled together in series between a first electrical contact 18 and a second electrical contact 20. The detector comprises at least a three regions or layers including a first layer 12 having a first type of electrical conductivity, a second layer 14 having a second type of electrical conductivity, and a third layer 16 having the first type of electrical conductivity. The first and second heterojunctions are coupled in series and function electrically as two back-to-back diodes. During use the detector is coupled to a switchable bias source 22 that includes a source of positive bias (+Vb) 22A and a source of negative bias (-Vb) 22B. With +Vb applied across the detector the first heterojunction is in far forward bias and functions as a low resistance conductor, thereby contributing no significant amount of photocurrent to the circuit. The second heterojunction is in a reverse bias condition and modulates the circuit current in proportion to the photon flux of an associated spectral region or color. Conversely, with -Vb applied across the detector the second heterojunction is in forward bias and contributes no significant photocurrent to the circuit while the first heterojunction is reversed biased and produces a current modulation proportional to the flux incident thereon, the flux being associated with a different spectral region.

Electronic transport properties of epitaxial erbium silicide/silicon heterostructures

Abstract: We studied electrical parallel and perpendicular transport in thin epitaxial erbium silicide films obtained by solid phase reaction and by codeposition of Er and Si on (111) Si. Resistivity measurements show that the silicide is metallic with a room‐temperature resistivity of 34 μΩ cm; the dependence of the Hall coefficient on temperature can be explained by a two‐band conduction model. Magnetic effects are shown to affect the low‐temperature resistivity and the Hall coefficient. Perpendicular transport properties are studied by electrical [current‐voltage I(V) and capacitance‐voltage C(V) characteristics] and internal photoemission methods on erbium silicide/n‐ or p‐type Si diodes. The p‐type diodes have a perfect rectifying behavior with a Schottky barrier height of about 0.74 eV measured by I(V) and photoemission methods. The n‐type junction is ohmic at room temperature and rectifying at low temperatures; C(V) and optical measurements yield a Schottky barrier height of about 0.28 eV. Some potential app...

GaAs SCHOTTKY BARRIER MIXER DIODES FOR THE FREQUENCY RANGE 1-10 THz~

Abstract: Recent technological advances have made possible the development of heterodyne receivers with high sensitivity and high spectral resolution for frequencies up to 3,000 GHz (3 THz). These receivers rely on GaAs Schottky barrier mixer diodes to translate the high-frequency signal to a lower frequency where amplification and signal processing are possible. In the frequency range from 1–10 THz several new effects will limit diode performance. These effects are discussed and guidelines for diode design are presented.

Resonant tunneling diodes for switching applications

Abstract: Rise times for simple pulse‐forming circuits are presented. Switching times for present best devices are in the range of 5–15 ps. An equivalent circuit model for resonant tunneling diodes inclusive of space‐charge effects and transit time effects in the depletion region is presented. From these models it is shown that switching times are limited by the device RC time constants and are relatively unaffected by the resonant state lifetime or depletion layer transit times. Appropriate figures of merit for switching applications are the device capacitance and peak current density. Less emphasis should be placed on improving the peak‐to‐valley ratio. Optimally designed devices which maximize the current density should be capable of switching in under 5 ps.

New principles of high power switching with semiconductor devices

Abstract: The present-day laser and accelerator technology, new types of radar, controlled fusion research and other areas of science and applications require very high power switching (MW to TW) in the micro-, nano-, subnanosecond ranges. The new principles of switching make use of semiconductor devices for such power switching. The principle of switching involving a controlling plasma layer has been employed to develop three new classes of devices, namely, reversely switched dynistors (RSD), reversely controlled transistors (RCT), and drift step-recovery diodes (DSRD). The highest-power microsecond-range RSDs switch 300 kA single pulse current, and 50 kA current at 100 Hz; high power DSRDs generate current pulses of 103 A in a few nanoseconds at frequencies > 104 Hz. The switching principle based on the impact ionization wave was used to develop diode pulse sharpeners (PS) switching power of a hundreds kW in tens of picoseconds at a frequency > 104 Hz. By this principal parameter, pulsed switching power, all these devices surpass the devices employing the conventional principles.

Light emitting diode array

Abstract: A light emitting diode lamp that operates directly from an AC input. The lamp has an even number of light emitting diodes that are disposed on a cylindrical cluster plate. The diodes are separated into two halves that are conductable in opposite electrical directions. The two halves of diodes are connected at two terminals. The diodes are arranged in a circular configuration near the edge of the circular cluster plate. Leads are connected to the terminals. The leads extend toward the center of the circular configuration and extend through the cluster plate. A modifying resistor is connected between one lead and an end terminal of a lamp housing. The other lead is connected to a base terminal of the lamp housing.

Characteristics of laser diodes for interferometric use.

Abstract: Low-coherence-length light from laser diode sources has applications in extending the useful range of interferometric fiber optic sensors. The characteristics of two commercial low-coherence laser diodes were investigated and compared with theoretical models to determine the operational characteristics of the devices. Reasonable trends in the comparison were seen.

Modeling and fabricating micro-cavity integrated vacuum tubes

Abstract: The authors discuss the modeling and fabricating miniature, vacuum, field-emission diodes and triodes for use in electronics in hazardous environments. They are micrometer-sized devices that are fabricated on a semiconductor wafer using integrated-circuit fabrication techniques and that use field emission rather than thermionic emission to generate charge carriers. Compared to existing semiconductor devices, they should be faster and much more tolerant of high temperatures and radiation. The device design uses the sacrificial layer technique to produce the device on a silicon wafer. All of the processing is completely compatible with existing integrated-circuit technology, making possible eventual integration of these devices and existing integrated-circuit components. To model these devices, the authors have used a static field modeling code to analyze the effect of device design variations on the field at the field-emission tip. Using these field results, they have calculated the tube's plate resistance, transconductance, gain, and current versus voltage characteristics. They have completed construction of a diode and are currently testing and interpreting the results. In addition, they have nearly completed a triode design. >

Efficient frequency noise reduction of GaAlAs semiconductor lasers by optical feedback from an external high-finesse resonator

Abstract: The reduction of frequency noise power level of non-antireflection-coated GaAlAs laser diodes by several orders of magnitude using optical feedback from an external high-finesse Fabry-Perot resonator is discussed. Optimum oscillation parameters were derived from a steady-state model. Long-term performance was obtained by electronic feedback phase control. >

Semiconductor device having a semiconductor region in which a band gap being continuously graded

Abstract: An improved semiconductor device such as an improved graded band gap transistor and an improved graded band gap diode, characterized by comprising a non-single-crystal material containing silicon atom, a band gap adjusting atom and a localized level reducing atom and having a region in which a band gap being continuously graded at least one position other than junction position and only one of a conduction band and a valence band being continuously graded. It gives a significant improvement in both the frequency characteristic and the photoresponse.

Semiconductor programmable memory device

Abstract: A field programmable device such as a PROM in which a memory cell is formed from a series connection of a capacitor and a diode or FET. Programming is performed by forming a short circuit in an insulation film of the capacitor due to electrical breakdown of the capacitor. The capacitor is formed of first and second semiconductor layers and an insulation film between the two layers. The instability of short circuits due to further oxidation of the insulation film is avoided by the above described structure. The memory stored in the device is stabilized, and the reliability of the device is increased. The insulation film of the capacitor is oxidized or nitrided by ion implantation of oxygen or nitrogen into the semiconductor substrate, or polycrystalline material.

Interface capacitance in metal‐semiconductor junctions

Abstract: A new theory of the interface capacitance at metal‐semiconductor junctions is presented. The diode capacitance is attributed to the modulation of the effective Schottky barrier height by interface charge. Relations between the measured capacitance and the physical properties of the interface states are formulated by using Shockley–Read statistics and taking into account the electron relaxation‐time dispersion. This theory is applied to NiSi2‐nSi diodes with both epitaxial and nonepitaxial interfaces. Spectra of density distribution, as well as other interface parameters, are obtained, indicating that interface states in these diodes are most probably defect related.

Theory of applied‐B ion diodes

Abstract: A recently introduced theory of applied‐B ion diodes [Phys Rev Lett 59, 2295 (1987)] is developed and presented in detail The theory incorporates the self‐consistent virtual cathode motion to obtain the steady‐state ion current as a function of diode voltage The existence of a limiting voltage at which the ion current diverges is demonstrated The voltage–current characteristics of the diode are combined with a simple circuit model of the accelerator to calculate the operating point of the diode The theoretical results are in good agreement with experimental data at peak power An important consequence of the theory is a relation between the limiting diode voltage and the insulating magnetic flux, suggesting a late‐time voltage decay driven by flux penetration into the anode plasma