Showing papers on "Diode published in 2001"

Active matrix light emitting diode pixel structure and concomitant method

Abstract: LED pixel structures and methods that improve brightness uniformity by reducing current nonuniformities in a light-emitting diode of the pixel structures are disclosed.

An efficient room-temperature silicon-based light-emitting diode.

Abstract: There is an urgent requirement for an optical emitter that is compatible with standard, silicon-based ultra-large-scale integration (ULSI) technology. Bulk silicon has an indirect energy bandgap and is therefore highly inefficient as a light source, necessitating the use of other materials for the optical emitters. However, the introduction of these materials is usually incompatible with the strict processing requirements of existing ULSI technologies. Moreover, as the length scale of the devices decreases, electrons will spend increasingly more of their time in the connections between components; this interconnectivity problem could restrict further increases in computer chip processing power and speed in as little as five years. Many efforts have therefore been directed, with varying degrees of success, to engineering silicon-based materials that are efficient light emitters. Here, we describe the fabrication, using standard silicon processing techniques, of a silicon light-emitting diode (LED) that operates efficiently at room temperature. Boron is implanted into silicon both as a dopant to form a p-n junction, as well as a means of introducing dislocation loops. The dislocation loops introduce a local strain field, which modifies the band structure and provides spatial confinement of the charge carriers. It is this spatial confinement which allows room-temperature electroluminescence at the band-edge. This device strategy is highly compatible with ULSI technology, as boron ion implantation is already used as a standard method for the fabrication of silicon devices.

High-power AlGaInN flip-chip light-emitting diodes

Abstract: Data are presented on high-power AlGaInN flip-chip light-emitting diodes (FCLEDs). The FCLED is “flipped-over” or inverted compared to conventional AlGaInN light-emitting diodes (LEDs), and light is extracted through the transparent sapphire substrate. This avoids light absorption from the semitransparent metal contact in conventional epitaxial-up designs. The power FCLED has a large emitting area (∼0.70 mm2) and an optimized contacting scheme allowing high current (200–1000 mA, J∼30–143 A/cm2) operation with low forward voltages (∼2.8 V at 200 mA), and therefore higher power conversion (“wall-plug”) efficiencies. The improved extraction efficiency of the FCLED provides 1.6 times more light compared to top-emitting power LEDs and ten times more light than conventional small-area (∼0.07 mm2) LEDs. FCLEDs in the blue wavelength regime (∼435 nm peak) exhibit ∼21% external quantum efficiency and ∼20% wall-plug efficiency at 200 mA and with record light output powers of 400 mW at 1.0 A.

Efficient silicon light-emitting diodes

Abstract: Considerable effort is being expended on the development of efficient silicon light-emitting devices compatible with silicon-based integrated circuit technology. Although several approaches are being explored, all presently suffer from low emission efficiencies, with values in the 0.01-0.1% range regarded as high. Here we report a large increase in silicon light-emitting diode power conversion efficiency to values above 1% near room temperature-close to the values of representative direct bandgap emitters of a little more than a decade ago. Our devices are based on normally weak one- and two-phonon assisted sub-bandgap light-emission processes. Their design takes advantage of the reciprocity between light absorption and emission by maximizing absorption at relevant sub-bandgap wavelengths while reducing the scope for parasitic non-radiative recombination within the diode. Each feature individually is shown to improve the emission efficiency by a factor of ten, which accounts for the improvement by a factor of one hundred on the efficiency of baseline devices.

Three-dimensional memory array and method of fabrication

Abstract: A multi-level memory array is described employing rail-stacks. The rail-stacks include a conductor and semiconductor layers. The rail-stacks are generally separated by an insulating layer used to form antifuses. In one embodiment, one-half the diode is located in one rail-stack and the other half in the other rail-stack.

Ultraviolet Emission From a Diamond Pn Junction

Abstract: We report the realization of an ultraviolet light–emitting diode with the use of a diamond pn junction. The pn junction was formed from a boron-doped p-type diamond layer and phosphorus-doped n-type diamond layer grown epitaxially on the {111} surface of single crystalline diamond. The pn junction exhibited good diode characteristics, and at forward bias of about 20 volts strong ultraviolet light emission at 235 nanometers was observed and was attributed to free exciton recombination.

Led integrated heat sink

Abstract: An electrically driven light emitting diode (LED) assembly comprising a light emitting diode ( 12 ), first ( 14 ) and second ( 16 ) electrical leads for conducting electricity to and from the light emitting diode ( 12 ), and a heat sink ( 18 ). The assembly is characterized by the first lead ( 14 ) including the heat sink ( 18 ) for conducting electricity and heat from the light emitting diode ( 12 ) through the heat sink ( 18 ). In other words, the diode ( 12 ) conducts electricity through a heat sink ( 18 ) allowing the diode ( 12 ) to be in electrical conductivity with the heat sink ( 18 ).

High Output Power InGaN Ultraviolet Light-Emitting Diodes Fabricated on Patterned Substrates Using Metalorganic Vapor Phase Epitaxy

Abstract: Ultraviolet (UV) light-emitting diodes (LEDs) with an InGaN multi-quantum-well (MQW) structure were fabricated on a patterned sapphire substrate (PSS) using a single growth process of metalorganic vapor phase epitaxy. In this study, the PSS with parallel grooves along the sapphire direction was fabricated by standard photolithography and subsequent reactive ion etching (RIE). The GaN layer grown by lateral epitaxy on a patterned substrate (LEPS) has a dislocation density of 1.5×108 cm-2. The LEPS-UV-LED chips were mounted on the Si bases in a flip-chip bonding arrangement. When the LEPS-UV-LED was operated at a forward-bias current of 20 mA at room temperature, the emission wavelength, the output power and the external quantum efficiency were estimated to be 382 nm, 15.6 mW and 24%, respectively. With increasing forward-bias current, the output power increased linearly and was estimated to be approximately 38 mW at 50 mA.

Application of an ultrathin LiF/Al bilayer in organic surface-emitting diodes

Abstract: Organic surface-emitting diodes have been constructed with a multilayer stacked cathode consisting of (1) an ultrathin LiF/Al bilayer acting as an effective electron injector, (2) an optically low-loss and electrically conducting silver intermediate layer for sheet resistance reduction, and (3) a transparent and nonconducting capping layer for refractive index matching to optimize optical transmission. The entire cathode structure is prepared by conventional thermal evaporation without incurring radiation damage, and the resulting organic surface-emitting diodes exhibit superior electrical and optical characteristics.

Efficient and high-power AlGaN-based ultraviolet light-emitting diode grown on bulk GaN

Abstract: By introducing thick bulk GaN as a substrate, we improved the performance of an AlGaN-based ultraviolet (UV) light-emitting diode (LED). The output power exceeds 3 mW at the injection current of 100 mA under a bare-chip geometry. Internal quantum efficiency is estimated as more than 80%, and the peak wavelength is 352 nm. The maximum power exceeds 10 mW at a large current injection of 400 mA, with an operation voltage of less than 6 V. These results indicate that an efficient UV LED is intrinsically possible by the combination of appropriate device design and the nitride substrate. By introducing packaging technology to enhance extraction efficiency, we will have a compact and efficient UV light source in the wide wavelength range of 200–360 nm, similar to conventional longer-wavelength LEDs.

Integrated circuit capacitor

Abstract: Use of different materials for different conductive films forming plates or electrodes of one or more capacitors formed in a trench in a body of semiconductor materials allow connections to be made selectively to the plates. The films may be undercut by different etchants at respective connection apertures to avoid formation of connections or connections made by doped polysilicon of different conductivities forming connections to some plates of similarly doped polysilicon and blocking diode junctions with oppositely doped polysilicon. The blocking diodes may include a compensation implant to adjust reverse breakdown characteristics and provide transient and electrostatic discharge protection.

Fabrication and Optoelectronic Properties of a Transparent ZnO Homostructural Light-Emitting Diode

Abstract: A transparent ZnO homostructural light-emitting diode (LED) with a structure of Au electrode/p(i)-ZnO film/n-ZnO single crystal/In electrode was fabricated using the technique of N2O plasma-enhanced pulsed laser reactive deposition. The contact between the p(i)-ZnO layer and n-ZnO wafer was found to exhibit nonlinear and rectifying current–voltage (I–V) characteristics. A current injection emission with bluish-white light was clearly observed at room temperature, and its intensity increased with increases in the injected electric current.

Diode-pumped Kerr-lens mode-locked Yb:KY(WO 4 ) 2 laser

Abstract: A self-starting Kerr-lens mode-locked Yb:KYWO42 laser directly end pumped by two 1.6-W diodes is demonstrated for what is to our knowledge the first time. Pulses as short as 71 fs with 120-mW average output power, at a center wavelength of 1057 nm, were obtained at a repetition rate of 110 MHz. A 10-nm tuning range was achieved with longer pulses and higher average output power.

Impact of texture-enhanced transmission on high-efficiency surface-textured light-emitting diodes

Abstract: The transmission properties of semiconductor surfaces can be changed by surface texturing. We investigate these changes experimentally and find that an enhancement of the angle-averaged transmission by a factor of 2 can be achieved with optimum texturing parameters. This enhanced transmission provides an additional light extraction mechanism for high-efficiency surface-textured light-emitting diodes. External quantum efficiencies of 46% and 54% are demonstrated before and after encapsulation, respectively.

Preferred embodiment to led light string

Abstract: An LED light string employs a plurality of LEDs wired in block series-parallel, where the one or more series blocks, each driven at the same input voltage as the source voltage (110 VAC or 220 VAC), are coupled in parallel. The LED light string interfaces to the source voltage using a common household plug; it may also include a corresponding common, household socket, coupled in electrical parallel, to enable multiple light strings to be connected to each other from end to end. In order to directly drive a network of diodes without current-limiting circuitry, the voltage of each series block of diodes must be matched to the input source voltage. This voltage matching requirement for direct AC drive places fundamental restrictions on the number of diodes on each diode series block, depending on the types of diodes used. For the voltage to be “matched,” in each series block, the peak input voltage must be less than or equal to the sum of the maximum diode voltages for each series block.

SiC power diodes provide breakthrough performance for a wide range of applications

Abstract: The electrical performance of silicon carbide (SiC) power diodes is evaluated and compared to that of commercially available silicon (Si) diodes in the voltage range from 600 V through 5000 V. The comparisons include the on-state characteristics, the reverse recovery characteristics, and power converter efficiency and electromagnetic interference (EMI). It is shown that a newly developed 1500-V SiC merged PiN Schottky (MPS) diode has significant performance advantages over Si diodes optimized for various voltages in the range of 600 V through 1500 V. It is also shown that a newly developed 5000 V SiC PiN diode has significant performance advantages over Si diodes optimized for various voltages in the range of 2000 V through 5000 V. In a test case power converter, replacing the best 600 V Si diodes available with the 1500 V SiC MPS diode results in an increase of power supply efficiency from 82% to 88% for switching at 186 kHz, and a reduction in EMI emissions.

Fabrication and characterization of ultraviolet-emitting diodes composed of transparent p-n heterojunction, p-SrCu2O2 and n-ZnO

Abstract: An ultraviolet light-emitting diode (UV-LED) was realized using a p-n heterojunction composed of the transparent oxide semiconductors p-SrCu2O2 and n-ZnO. A Ni/SrCu2O2/ZnO/ITO multilayered film was epitaxially grown on an extremely flat YSZ (111) surface by a pulsed-laser deposition technique. SrCu2O2 (112) was preferentially grown on ZnO (0001) at 350°C, while the preferential plane was changed into the (100) when the temperature was increased to 600 °C. The grown films were processed by conventional photolithography followed by reactive ion etching to fabricate heterojunction diodes. The resulting devices exhibited rectifying I-V characteristics inherent to p-n junctions. A relatively sharp electroluminescence band centered at 382 nm, attributed to transitions associated with exciton-exciton collision or electron-hole plasma in ZnO, was generated by applying a forward bias voltage greater than the turn-on voltage of 3 V. UV-LED performance characteristics such as threshold current and conversion efficie...

Light-emitting element, semiconductor light-emitting device, and manufacturing methods therefor

Abstract: A GaN-based LED element 1 having a double heterostructure, which includes a GaN layer and the like and is formed on a sapphire substrate, is mounted face-down on a Si diode element 2 formed in a silicon substrate. Electrical connections are provided via Au microbumps 11 and 12 between a p-side electrode 5 of the GaN-based LED element 1 and an n-side electrode 8 of the Si diode element 2 and between an n-side electrode 6 of the GaN-based LED element 1 and a p-side electrode 7 of the Si diode element 2. The Si diode element 2 functions to protect the LED element 1 from an electrostatic destruction. The Si diode element 2 has a backside electrode 9 connected to a leadframe 13 a. The p-side electrode 7 of the Si diode element 2 has a bonding pad portion 10 connected to a leadframe 13 b via an Au wire 17.

Correlation between leakage current density and threading dislocation density in SiGe p-i-n diodes grown on relaxed graded buffer layers

Abstract: A correlation between bulk leakage current density and threading dislocation density in silicon–germanium mesa-isolated diodes fabricated on relaxed graded buffer layers is presented. Si0.75Ge0.25 p-i-n diodes were grown on SiGe graded buffers with different grading rates. Graded buffers with different grading rates yielded “virtual substrates” with varying densities of threading dislocations. Bulk leakage current densities were differentiated from surface leakage currents by using p-i-n diodes with different areas. We demonstrate that the increase in bulk leakage current density in SiGe p-i-n diodes can be modeled by generation processes assisted by deep levels related to threading dislocations.

Emission properties of different cathodes at E⩽105 V/cm

Abstract: We present results of the investigation of different types of cathodes operating in an electron diode powered by a high-voltage generator (300 kV, 250 ns, 84 Ω, ⩽5 Hz). The cathodes which have the same emitting area of 100 cm2 are made of metal–ceramic, carbon fibers, carbon fabric, velvet, or corduroy. We also tested carbon fibers and carbon fabric cathodes coated by CsI. It was shown that for all types of cathodes the electron emission occurs from the plasma which is formed as a result of a flashover of separate emitting centers. The amount of the emitting centers and the time delay in the electron emission were found to depend strongly on the accelerating electric field growth rate. Experimental data concerning the uniformity of the light emission from the cathode surface and divergence of the generated electron beams are presented. Data related to the general parameters of the diode, namely its impedance, power, and energy are given as well. For all the cathodes investigated the observed diode impedance indicated the existence of a quasistationary cathode plasma boundary for electron current density ⩽20 A/cm2. We present the dependencies of the average emitted electron current density and of the time delay in the electron emission on the number of generator shots. We also present data of the vacuum deterioration as a result of the tested cathodes operation. The obtained data are discussed within the framework of plasma formation as a result of cathode surface flashover.

Gallium nitride material devices and methods including backside vias

Abstract: The invention includes providing gallium nitride material devices having backside vias and methods to form the devices. The devices include a gallium nitride material formed over a substrate, such as silicon. The device also may include one or more non-conducting layers between the substrate and the gallium nitride material which can aid in the deposition of the gallium nitride material. A via is provided which extends from the backside of the device through the non-conducting layer(s) to enable electrical conduction between an electrical contact deposited within the via and, for example, an electrical contact on the topside of the device. Thus, devices of the invention may be vertically conducting. Exemplary devices include laser diodes (LDs), light emitting diodes (LEDs), power rectifier diodes, FETs (e.g., HFETs), Gunn-effect diodes, and varactor diodes, among others.

Unipolar spin diodes and transistors

Abstract: Unipolar devices constructed from ferromagnetic semiconducting materials with variable magnetization direction are shown theoretically to behave very similarly to nonmagnetic bipolar devices such as the p-n diode and the bipolar (junction) transistor. Such devices may be applicable for magnetic sensing, nonvolatile memory, and reprogrammable logic.

Temperature dependent write current source for magnetic tunnel junction MRAM

Abstract: An MRAM storage device includes temperature dependent current sources that adjust their outputs as temperature varies. Temperature dependent current sources include one or more diodes connected to a transistor. As temperature varies so does the voltage drop across the diodes. In addition, the MRAM data storage device includes at least one digit line, at least one bit line, and at least one MRAM cell disposed proximate to a junction of a digit line and a bit line. Each end of each digit line is connected to temperature dependent current sources and current sinks. One end of each bit line is connected to a temperature dependent current source while the other end of each bit line is connected to a current sink. Two logic signals R and D are used to activate a write operation and determine the direction of the write current in the digit line.

Theoretical modeling and experimental characterization of a rod-pinch diode

Abstract: The rod-pinch diode consists of an annular cathode and a small-diameter anode rod that extends through the hole in the cathode. With high-atomic-number material at the tip of the anode rod, the diode provides a small-area, high-yield x-ray source for pulsed radiography. The diode is operated in positive polarity at peak voltages of 1 to 2 MV with peak total electrical currents of 30–70 kA. Anode rod diameters as small as 0.5 mm are used. When electrode plasma motion is properly included, analysis shows that the diode impedance is determined by space-charge-limited current scaling at low voltage and self-magnetically limited critical current scaling at high voltage. As the current approaches the critical current, the electron beam pinches. When anode plasma forms and ions are produced, a strong pinch occurs at the tip of the rod with current densities exceeding 106 A/cm2. Under these conditions, pinch propagation speeds as high as 0.8 cm/ns are observed along a rod extending well beyond the cathode. Even f...

Unipolar spin diodes and transistors

Abstract: Unipolar devices constructed from ferromagnetic semiconducting materials with variable magnetization direction are shown theoretically to behave very similarly to nonmagnetic bipolar devices such as the p-n diode and the bipolar (junction) transistor. Such devices may be applicable for magnetic sensing, nonvolatile memory, and reprogrammable logic.

A dual-wavelength indium gallium nitride quantum well light emitting diode

Abstract: We have designed and implemented a monolithic, dual-wavelength blue/green light emitting diode (LED) consisting of two active indium gallium nitride/gallium nitride (InGaN/GaN) multiple-quantum-well segments. The segments are part of a single vertical epitaxial structure in which a p++/n++ InGaN/GaN tunnel junction is inserted between the LEDs, emitting in this proof-of-concept device at 470 nm and 535 nm, respectively. The device has been operated as a three-terminal device with independent electrical control of each LEDs to a nanosecond time scale.

A Spin Esaki Diode

Abstract: We demonstrate electrical electron spin injection via interband tunneling in ferromagnetic/nonmagnetic semiconductor Esaki diodes. An interband tunnel junction between ferromagnetic p+-(Ga,Mn)As and nonmagnetic n+-GaAs under reverse-bias allows spin-polarized tunneling of electrons from the valence band of (Ga, Mn)As to the conduction band of n+-GaAs. The spin polarization of tunneled electrons is probed by circular polarization of electroluminescence (EL) from an n-GaAs/InGaAs/p-GaAs light emitting structure integrated with the diode. Clear hysteresis loop with ±6.5% remanence is observed in the magnetic-field dependence of the EL polarization at 6 K, below the Curie temperature of (Ga, Mn)As.

Semiconductor light-emitting device

Abstract: PROBLEM TO BE SOLVED: To obtain a semiconductor light-emitting device without any absorption of emission light from an active layer and with improved cooling properties. SOLUTION: A light-emitting diode device is transparent to emission light and has relatively high thermal conductivity, and a substrate 11 made of n-type GaN where the orientation of a main surface has (0001) face. On the substrate 11, a buffer layer 12 that is made of an n-type GaAs as thick as approximately 1 μm and relaxes the lattice mismatching between the substrate 11 and each semiconductor layer on the substrate 11, a first clad layer 13 that is made of an n-type AlGaAS that is approximately 0.5 μm and entraps carriers contributing to emission into a light emission layer 14, the light emission layer 14 that is made of undoped AlGaAs that is as thick as approximately 0.1 μm and generates emission light by recombining the entrapped carriers, and a second clad layer 15 that is made of a p-type AlGaAs with a thickness of approximately 0.5 μm and entraps the carriers into the light emission layer 14 are successively formed.