Showing papers on "Diode published in 2000"

ZnO diode fabricated by excimer-laser doping

Abstract: A ZnO diode was fabricated by using a laser-doping technique to form a p-type ZnO layer on an n-type ZnO substrate. A zinc-phosphide compound, used as a phosphorous source, was deposited on the ZnO wafer and subjected to excimer-laser pulses. The current–voltage characteristics showed a diode characteristic between the phosphorous-doped p-layer and the n-type substrate. Moreover, light emission, with a band-edge component, was observed by forward current injection at 110 K.

Light-radiating semiconductor component with a luminescence conversion element

Abstract: The light-radiating semiconductor component has a radiation-emitting semiconductor body and a luminescence conversion element. The semiconductor body emits radiation in the ultraviolet, blue and/or green spectral region and the luminescence conversion element converts a portion of the radiation into radiation of a longer wavelength. This makes it possible to produce light-emitting diodes which radiate polychromatic light, in particular white light, with only a single light-emitting semiconductor body. A particularly preferred luminescence conversion dye is YAG:Ce.

Improving the Performance of Doped pi-Conjugated Polymers for Use in Organic Light-Emitting Diodes

Abstract: Organic light-emitting diodes (OLEDs) represent a promising technology for large, flexible, lightweight, flat-panel displays. Such devices consist of one or several semiconducting organic layer(s) sandwiched between two electrodes. When an electric field is applied, electrons are injected by the cathode into the lowest unoccupied molecular orbital of the adjacent molecules (simultaneously, holes are injected by the anode into the highest occupied molecular orbital). The two types of carriers migrate towards each other and a fraction of them recombine to form excitons, some of which decay radiatively to the ground state by spontaneous emission. Doped pi-conjugated polymer layers improve the injection of holes in OLED devices; this is thought to result from the more favourable work function of these injection layers compared with the more commonly used layer material (indium tin oxide). Here we demonstrate that by increasing the doping level of such polymers, the barrier to hole injection can be continuously reduced. The use of combinatorial devices allows us to quickly screen for the optimum doping level. We apply this concept in OLED devices with hole-limited electroluminescence (such as polyfluorene-based systems), finding that it is possible to significantly reduce the operating voltage while improving the light output and efficiency.

Current injection emission from a transparent p–n junction composed of p-SrCu2O2/n-ZnO

Abstract: An ultraviolet light-emitting diode (LED) operating at room temperature was realized using a p–n heterojunction composed of transparent conductive oxides, p-SrCu2O2 and n-ZnO. Multilayered films prepared by a pulsed-laser deposition technique were processed by conventional photolithography with the aid of reactive ion etching to fabricate the LED device. A rather sharp emission band centered at 382 nm was generated when a forward bias voltage exceeding the turn-on voltage of 3 V was applied to the junction. The emission may be attributed to a transition associated with the electron–hole plasma of ZnO.

Fabrication and performance of GaN electronic devices

Abstract: GaN and related materials (especially AlGaN) have recently attracted a lot of interest for applications in high power electronics capable of operation at elevated temperatures. Although the growth and processing technology for SiC, the other viable wide bandgap semiconductor material, is more mature, the AlGaInN system offers numerous advantages. These include wider bandgaps, good transport properties, the availability of heterostructures (particularly AlGaN/GaN), the experience base gained by the commercialization of GaN-based laser and light-emitting diodes and the existence of a high growth rate epitaxial method (hydride vapor phase epitaxy) for producing very thick layers or even quasi-substrates. These attributes have led to rapid progress in the realization of a broad range of GaN electronic devices, including heterostructure field effect transistors (HFETs), Schottky and p–i–n rectifiers, heterojunction bipolar transistors (HBTs), bipolar junction transistors (BJTs) and metal-oxide semiconductor field effect transistors (MOSFETs). This review focuses on the development of fabrication processes for these devices and the current state-of-the-art in device performance, for all of these structures. We also detail areas where more work is needed, such as reducing defect densities and purity of epitaxial layers, the need for substrates and improved oxides and insulators, improved p-type doping and contacts and an understanding of the basic growth mechanisms.

Improvement of output coupling efficiency of organic light-emitting diodes by backside substrate modification

Abstract: The emission intensity of an organic light-emitting diode at normal viewing angle and the total external emission efficiency have been increased by factors of 9.6 and 3.0, respectively, by applying spherically shaped patterns to the back of the device substrate. The technique captures light previously lost to waveguiding in the substrate and, with proper choice of substrate, light previously lost to waveguiding in the organic/anode layers. A method of applying the technique using laminated films and an optical model for evaluating coupling efficiency are also presented.

Pulse oximetry sensor compatible with multiple pulse oximetry systems

Abstract: An oximeter sensor can be used with multiple oximeter systems. The oximeter sensor includes a first light-emitting diode, a second light-emitting diode and a photodetector. Electrical connections to the anode and the cathode of each light-emitting diode and electrical connections to the terminals of the photodetector are provided on a connector. An interconnector is interposed between the connector of the oximeter sensor and a connector in communication with an oximeter system. The interconnector has interconnection wiring selected to electrically connect the sensor connector and the system connector in a manner to configure the light-emitting diodes in a configuration compatible with the oximeter system. In particular, a first interconnector configures the light-emitting diodes in a common anode arrangement. A second interconnector configures the light-emitting diodes in a back-to-back (anode to cathode, cathode to anode) configuration. Either interconnector may be in the form of a shell having two connectors. Alternatively, either interconnector may be in the form of a flexible cable with connectors at each end.

Hybrid integrated circuit device

Abstract: Disclosed is a hybrid integrated circuit device provided with an active filter. The active filter is constructed mainly from a rectifier circuit, a reactor with one terminal connected with an output terminal of the rectifier, a switching element connected with one terminal of the reactor and a smoothing condenser connected with the other terminal of the reactor. The active filter is mounted on an insulating metal substrate and has, other than the above feature, a specific circuit structure wherein the substrate is divided by a ground pattern or power supply pattern into two blocks. One block is for a large current circuit such as the rectifier circuit, the switching element, and a diode and another block for a small signal circuit such as a control circuit. The hybrid integrated circuit device is of remarkably compact size. Also, it is greatly superior in a noise performance because switching noise does not flow into the chassis of electronic equipment from the metal substrate and the control circuit is shielded from the noise produced by the large current circuit, and also because the noise caused by wiring inductance can be limited.

Surface plasmon enhanced light-emitting diode

Abstract: A method for enhancing the emission properties of light-emitting diodes, by coupling to surface plasmons, is analyzed both theoretically and experimentally. The analyzed structure consists of a semiconductor emitter layer thinner than /spl lambda//2 sandwiched between two metal films. If a periodic pattern is defined in the top semitransparent metal layer by lithography, it is possible to efficiently couple out the light emitted from the semiconductor and to simultaneously enhance the spontaneous emission rate. For the analyzed designs, we theoretically estimate extraction efficiencies as high as 37% and Purcell factors of up to 4.5. We have experimentally measured photoluminescence intensities of up to 46 times higher in fabricated structures compared to unprocessed wafers. The increased light emission is due to an increase in the efficiency and an increase in the pumping intensity resulting from trapping of pump photons within the microcavity.

Light emitting diode light strip

Abstract: A light emitting diode light strip that uses a rigid hollow tube ( 20 ) sized to accommodate a printed circuit board ( 22 ) which has a positive and negative bus extending the full length of the board. One or more resistors ( 38 ) are in contact with the positive bus on one end and a series of light emitting diodes ( 44 ) on the other. The diodes are mounted through holes ( 34 ) in the board and the anode of the diode is in communication with a resistor while the cathode of the diode contacts an adjacent diode anode connecting them in linked series through traces on the bottom of the circuit board. The end cathode in each series, engages the negative bus forming a predetermined group of diodes electrically coupled to a single resistor on one end and the negative bus on the other. A pair of end caps ( 50 ) enclose the tube and an electrical cable ( 60 ) is connected through the caps to the busses on the circuit board. A power supply ( 64 ) is in contact, through the electrical cable, with the board providing low voltage direct current power through the busses to a predetermined group of light emitting diodes, for illumination of the area surrounding the light strip.

Blue InGaN-based laser diodes with an emission wavelength of 450 nm

Abstract: Blue InGaN single-quantum-well-structure laser diodes (LDs) with an emission wavelength of 450 nm were grown on an epitaxially laterally overgrown GaN substrate by a metalorganic chemical vapor deposition method. The threshold current density and voltage were 4.6 kA cm−2 and 6.1 V, respectively. The estimated lifetime was approximately 200 h under room-temperature continuous-wave operation at an output power of 5 mW. When the number of InGaN well layers of the LDs with emission wavelengths longer than 435 nm varied from one to three, the lowest threshold current density was obtained when the number of well layers was one.

Passively mode-locked diode-pumped surface-emitting semiconductor laser

Abstract: A surface-emitting semiconductor laser has been passively mode locked in an external cavity incorporating a semiconductor saturable absorber mirror. The gain medium consists of a stack of 12 InGaAs-GaAs strained quantum wells, grown above a Bragg mirror structure, and pumped optically by a high-brightness diode laser. The mode-locked laser emits pulses of 22-ps full-width at half maximum duration at 1030 nm, with a repetition rate variable around 4.4 GHz.

Diode-pumped femtosecond Yb:KGd(WO(4))(2) laser with 1.1-W average power.

Abstract: We demonstrate what is to our knowledge the first mode-locked Yb:KGd(WO4)2 laser. Using a semiconductor saturable-absorber mirror for passive mode locking, we obtain pulses of 176-fs duration with an average power of 1.1 W and a peak power of 64 kW at a center wavelength of 1037 nm. We achieve pulses as short as 112 fs at a lower output power. The laser is based on a standard delta cavity and pumped by two high-brightness laser diodes, making the whole system very simple and compact. Tuning the laser by means of a knife-edge results in mode-locked pulses within a wavelength range from 1032 to 1054 nm. In cw operation, we achieve output powers as high as 1.3 W.

Comparative dosimetry in narrow high-energy photon beams.

Abstract: A comparison of the response of different dosimeters in narrow photon beams (phi > or = 4 mm) of 6 and 18 MV bremsstrahlung has been performed The detectors used were a natural diamond detector, a liquid ionization chamber, a plastic scintillator and two dedicated silicon diodes The diodes had a very small detection volume and one was a specially designed double diode using two parallel opposed active volumes with compensating interface perturbations The characteristics of the detectors were investigated both for dose distribution measurements, such as depth-dose curves and lateral beam profiles, and for output factors The dose rate and angular dependence of the diamond and the two diodes were also studied separately The depth-dose distributions for small fields agree well for the diamond, the scintillator and the single diode, while the measured dose maximum for the double diode is about 1% higher and for the liquid chamber about 1% lower than the mean of the others when normalized at a depth of 10 cm The plastic scintillator and the liquid ionization chamber detect a penumbra width that is slightly broadened due to the influence of their finite size, while the double diode may even underestimate the penumbra width due to its small size and high density When corrected for the extension of the detector volume a good agreement with Monte Carlo calculated beam profiles was obtained for the plastic scintillator and the liquid ionization chamber Profiles measured with the diamond show an asymmetry when positioned with the smallest dimension facing the beam, while the double diode, the scintillator and the liquid chamber measure symmetric profiles irrespective of positioning Significant differences in the output factors were obtained with the different detectors The natural diamond detector measures output factors close to those with an ionization chamber (less than 1% difference) for field sizes between 3 x 3 and 15 x 15 cm2, but overestimates the output factors for large fields and underestimates the output factors for the smallest field sizes The single and double diodes overestimated the output factor for large field sizes by up to 7 and 12% respectively due to the high content of low-energy photons The double diode, and to some extent the single diode, also showed a relative increase in response compared with the more water equivalent liquid chamber and plastic scintillator at the smallest fields where there is a lack of lateral electron equilibrium Both the plastic scintillator and the liquid chamber also show responses that deviate from the ionization chamber for larger field sizes The major deviations can be explained based on the characteristics of the sensitive materials and the construction of the detectors

Functionalized oligoarylenes as building blocks for new organic materials

Abstract: Some of the current directions in research on new organic materials based on functionalized oligoarylenes are reviewed. Particular emphasis is placed upon the use of chemical synthesis for the incorporation of suitable functionalized oligoarylenes into more complex molecular and polymeric systems. Selected examples of applications of these materials in different fields such as light-emitting diodes, photovoltaic devices, nonlinear optics, two-photon dyes, molecular switches or ligands will be presented.

Blue cooperative upconversion in Yb3+-doped multicomponent sol-gel-processed silica glass for three-dimensional display

Abstract: We propose using blue cooperative upconversion of ytterbium (Yb3+) ions produced by a one-color one-beam pumping scheme for a three-dimensional fluorescence display. The results are presented using a diode laser as a pump source emitting at 973 nm, and the sample used was a multicomponent sol-gel-processed silica glass (1 mol. % of Yb3+). The maximum absolute blue power emitted was ∼1 μW for an excitation power of ∼900 mW.

Control of color and efficiency of light-emitting diodes based on polyfluorenes blended with hole-transporting molecules

Abstract: Adding low-molecular-weight hole-transporting molecules (HTM) with different oxidation potentials to the polyfluorene emission layer of single-layer light-emitting diodes causes significant changes in the device properties The pronounced increase in luminance efficiency combined with a decrease in current is attributed to significant hole trapping, as further suggested by thermoluminescence experiments Using a oligo-triphenylamine HTM with an ionization potential of ∼49 eV, light-emitting diodes with stable blue emission, a brightness of 800 cd/m2 and an efficiency of 087 cd/A were realized Further, the red-emitting contribution to the spectra as observed in the pure polymer devices could be fully suppressed

Semiconductor Devices: Basic Principles

Abstract: Electrons in Solids Electrons in Semiconductors Carrier Dynamics in Semiconductors Processing of Devices: A Review Junctions in Semiconductors: P-N Diodes Semiconductor Junctions with Metals and Insulators Bipolar Junction Transistors Field Effect Transistors: JFET/MESFET Field Effect Transistors: MOSFET MOSFET: Technology Driver Semiconductor Optoelectronics Appendices Index

GaN microdisk light emitting diodes

Abstract: Microdisk light-emitting diodes (μ-LEDs) with diameter of about 12 μm have been fabricated from InGaN/GaN quantum wells. Photolithographic patterning and inductively coupled plasma dry etching have been employed to fabricate these μ-LED devices. Device characteristics, such as the current–voltage characteristics, light output power, and electroluminescence (EL) spectra have been measured and compared with those of conventional broad-area LEDs. Our results showed that, for an identical area, the quantum efficiencies of μ-LED are enhanced over the conventional broad-area LEDs due to an enhanced current density and possibly microsize effects. The implications of our results on the design of future UV/blue microoptoelectronic devices are discussed.

Transition dipole moment of InAs/InGaAs quantum dots from experiments on ultralow-threshold laser diodes

Abstract: Semiconductor ultralow-threshold InAs quantum-dot lasers are investigated operating at 1230–1250 nm at room temperature (laser threshold range is of 16–83 A/cm2 for ground-state emission). The dependence of gain on current is derived from measurements of the threshold current as a function of the cavity length. The ground-state gain appears at very low current: the inversion threshold of ∼13 A/cm2 is a record low value. Analysis of these data for diodes of different molecular beam epitaxial-grown wafers leads to a squared dipole moment of the transition of ∼9.2×10−57 C2 m2 that corresponds to the length of elementary dipole of ∼0.6 nm.

Surface Recombination Measurements on III-V Candidate Materials for Nanostructure Light-Emitting Diodes

Abstract: Surface recombination is an important characteristic of an optoelectronic material. Although surface recombination is a limiting factor for very small devices it has not been studied intensively. We have investigated surface recombination velocity on the exposed surfaces of the AlGaN, InGaAs, and InGaAlP material systems by using absolute photoluminescence quantum efficiency measurements. Two of these three material systems have low enough surface recombination velocity to be usable in nanoscale photonic crystal light-emitting diodes.

Selective Area Deposited Blue GaN-InGaN Multiple-Quantum Well Light Emitting Diodes over Silicon Substrates

Abstract: We report on fabrication and characterization of blue GaN–InGaN multi-quantum well (MQW) light-emitting diodes (LEDs) over (111) silicon substrates. Device epilayers were fabricated using unique combination of molecular beam epitaxy and low-pressure metalorganic chemical vapor deposition growth procedure in selective areas defined by openings in a SiO2 mask over the substrates. This selective area deposition procedure in principle can produce multicolor devices using a very simple fabrication procedure. The LEDs had a peak emission wavelength of 465 nm with a full width at half maximum of 40 nm. We also present the spectral emission data with the diodes operating up to 250 °C. The peak emission wavelengths are measured as a function of both dc and pulse bias current and plate temperature to estimate the thermal impedance.

GaInAsN/GaAs laser diodes operating at 1.52 [micro sign]m

Abstract: GaInAsN/GaAs double quantum well (DQW) lasers have been grown by solid source molecular beam epitaxy (MBE). Room-temperature pulsed operation is demonstrated for a ridge waveguide laser diode at a wavelength of 1517 nm. This is the first report of room-temperature laser emission in the 1.5 /spl mu/m range based on GaAs.

Lower electrode isolation in a double-wide trench

Abstract: The invention relates to a phase-change memory device. The device includes a double-wide trench into which a single film is deposited but two isolated lower electrodes are formed therefrom. Additionally a diode stack is formed that communicates to the lower electrode. Additionally, other isolated lower electrodes may be formed along a symmetry line that is orthogonal to the first two isolated lower electrodes. The present invention also relates to a method of making a phase-change memory device. The method includes forming two orthogonal and intersecting isolation structure s around a memory cell structure diode stack.

Effects of thin oxide in metal-semiconductor and metal-insulator-semiconductor epi-GaAs Schottky diodes

Abstract: The current–voltage (I–V) and capacitance–voltage (C–V) characteristics of metal–insulator–semiconductor (MIS) GaAs Schottky diodes are investigated and compared with metal–semiconductor (MS) diodes. The MIS diode showed nonideal behavior of I–V characteristics with an ideality factor of 1.17 and a barrier height of 0.97 eV. The energy distribution of interface states density was determined from the forward bias I–V characteristics by taking into account the bias dependence of the effective barrier height, though it is small. The reduction in the saturation current in the MIS case is caused by a thin oxide layer and is due to the combination of increased barrier height and a decrease in the Richardson constant. The carrier concentration anomaly observed between the MIS and MS diodes measured from reverse bias C–V measurements is explained via oxide $(\beta-Ga_2O_3)$ traps due to the Ga-vacancy by deep level transient spectroscopy (DLTS) measurement.

A unified simulation of Schottky and ohmic contacts

Abstract: The Schottky contact is an important consideration in the development of semiconductor devices. This paper shows that a practical Schottky contact model is available for a unified device simulation of Schottky and ohmic contacts. The present model includes the thermionic emission at the metal/semiconductor interface and the spatially distributed tunneling calculated at each semiconductor around the interface. Simulation results of rectifying characteristics of Schottky barrier diodes (SBD's) and resistances under high impurity concentration conditions are reasonable, compared with measurements. As examples of application to actual devices, the influence of the contact resistance on salicided MOSFETs with source/drain extension and the immunity of Schottky barrier tunnel transistors (SBTTs) from the short-channel effect (SCE) are demonstrated.

Electro-luminescent display including a current mirror

Abstract: An electro-luminescent display includes a current mirror for supplying uniform drive currents to the electro-luminescent diodes of the electro-luminescent display. The current mirror is not effected by the various threshold voltages V TH of the switching devices in the electro-luminescent display so that uniform current is output to the electro-luminescent diodes throughout the display. The electro-luminescent display includes a gate line, a data line intersecting the gate line, a first TFT for selecting an arbitrary pixel by a gate signal from the gate line, wherein a gate of the first TFT is connected to the gate line, and a current mirror for outputting a signal to an arbitrary pixel selected by the first TFT by receiving a data signal from the data line at the same time the current mirror is being driven by applied voltage. The current mirror includes a second TFT and a third TFT, and an electro-luminescent diode driven by the signal output from the current mirror.

Rate-equation analysis of output efficiency and modulation rate of photonic-crystal light-emitting diodes

Abstract: The performance characteristics of photonic-crystal light-emitting diodes (LEDs) are analyzed, taking into account the effects of both nonradiative recombination and photon reabsorption processes using multimode rate equations. It is shown that, in the presence of strong photon reabsorption, the optimum output efficiency and modulation rates are achieved when the width of the photon density-of-state distribution function is comparable to the width of the spontaneous emission lineshape of the active material. On the other hand, when photon reabsorption is weak, it becomes beneficial to construct high-Q cavities. Based on this analysis, the characteristics of different photonic crystal LED configurations are discussed.

Room-temperature operation at 333 nm of Al0.03Ga0.97N/Al0.25Ga0.75N quantum-well light-emitting diodes with Mg-doped superlattice layers

Abstract: We demonstrate room-temperature deep ultraviolet (UV) current injection emission from Al0.03Ga0.97N/Al0.25Ga0.75N multiquantum-well (MQW) light-emitting diodes (LEDs) fabricated by metalorganic vapor phase epitaxy. The electroluminescence (EL) peaked at 333.0 nm under pulsed current injection. To our knowledge, this is the shortest wavelength ever reported for nitride QW LEDs. A Mg-doped GaN/AlGaN superlattice (SL) hole conductive layer was used as a p-type layer in order to enable current injection into such deep-level AlGaN QWs. We observed single-peak near band-edge emission from the QWs. The output intensity did not saturate up to current densities of 0.33 kA/cm2. We obtained a reasonable well width dependence on the EL peak wavelength of Al0.01Ga0.99N MQW LEDs, which confirms that the main emission peak originates from the QW regions. These results revealed that the Mg-doped SL hole conductive layers are highly suitable for application to GaN-based UV light-emitting devices.

Lithium−Quinolate Complexes as Emitter and Interface Materials in Organic Light-Emitting Diodes

Abstract: We synthesized lithium−quinolate complexes, 8-hydroxyquinolinolatolithium (Liq) and 2-methyl-8-hydroxyquinolinolatolithium (LiMeq), as emitter and electron injection/transport materials to be used in conventional two-layer organic light-emitting diodes in combination with N,N‘-bis(p-methoxyphenyl)-N,N‘-diphenylbenzidine (DMeOTPD) as hole transport material (HTL). The lithium complexes were also examined as interface materials in combination with 8-hydroxyquinolinolato-Al(III) (Alq3) as emitter material. The device efficiency with these complexes was optimized by combinatorial methods. We also compared the electron injection, transport, and emission properties of Li complexes with the well-known emitter Alq3 in the same experiment by taking advantage of the combinatorial approach. The Li quinolates are found to be efficient emitter molecules. But the efficiencies of lithium quinolate devices are lower than that of Alq3 devices. Contrary to the Alq3 emission, the Li quinolates exhibit a bathochromic shift o...