Showing papers on "Diode published in 2012"

Graphene Barristor, a Triode Device with a Gate-Controlled Schottky Barrier

Abstract: Despite several years of research into graphene electronics, sufficient on/off current ratio I(on)/I(off) in graphene transistors with conventional device structures has been impossible to obtain. We report on a three-terminal active device, a graphene variable-barrier "barristor" (GB), in which the key is an atomically sharp interface between graphene and hydrogenated silicon. Large modulation on the device current (on/off ratio of 10(5)) is achieved by adjusting the gate voltage to control the graphene-silicon Schottky barrier. The absence of Fermi-level pinning at the interface allows the barrier's height to be tuned to 0.2 electron volt by adjusting graphene's work function, which results in large shifts of diode threshold voltages. Fabricating GBs on respective 150-mm wafers and combining complementary p- and n-type GBs, we demonstrate inverter and half-adder logic circuits.

AlGaN Deep-Ultraviolet Light-Emitting Diodes with External Quantum Efficiency above 10%

Abstract: Improvements of the internal quantum efficiency by reduction of the threading dislocation density and of the light extraction by using UV transparent p-type cladding and contact layers, UV reflecting ohmic contact, and chip encapsulation with optimized shape and refractive index allowed us to obtain the external quantum efficiency of 104% at 20 mA CW current with the output power up to 93 mW at 278 nm for AlGaN-based deep-ultraviolet light-emitting diodes grown on sapphire substrates

Metal--Semiconductor Schottky Barrier Junctions and Their Applications

Abstract: 1. Physics of Schottky Barrier Junctions.- 1. Introduction.- 2. Origins of Barrier Height.- 2.1. Schottky-Mott Theory of Ideal Metal-Semiconductor Contact.- 2.2. Modifications to Schottky Theory.- 2.3. Classifications of Metal-Semiconductor Interfaces.- 2.4. Contacts on Reactive Interfaces.- 2.5. Contacts with Surface States and an Insulating Interfacial Layer.- 2.6. Contacts on Vacuum Cleaved Surfaces.- 3. Measurement of Barrier Height.- 3.1. Capacitance-Voltage Measurement.- 3.2. Current-Voltage Measurement.- 3.3. Photoelectric Measurement.- 4. Results of Barrier Height Measurements.- 4.1. Chemically Prepared Surfaces.- 4.2. Vacuum Cleaved Surfaces.- 4.3. Concluding Remarks.- 5. Capacitance-Voltage Characteristics.- 5.1. Electric Field and Potential Distribution in the Depletion Region.- 5.2. Depletion Region Capacitance.- 5.2.1. Ideal Schottky Barrier.- 5.2.2. Effect of Minority Carriers.- 5.2.3. Effect of Interfacial Layer.- 5.2.4. Effect of Deep Traps.- 6. Current-Voltage Characteristics.- 6.1. Transport Mechanisms.- 6.1.1. Diffusion and Thermionic Emission over the Barrier.- 6.1.2. Tunneling through the Barrier.- 6.1.3. Carrier Generation and Recombination in the Junction Depletion Region.- 6.1.4. Minority Carrier Injection.- 6.2. Forward Characteristics.- 6.3. Reverse Characteristics.- 7. Transient Behavior.- 8. Low-Resistance Schottky Barrier Contacts.- References.- 2. Interface Chemistry and Structure of Schottky Barrier Formation.- 1. Introduction.- 2. Perspectives on Schottky Barrier Formation.- 2.1. Introduction.- 2.2. Brief Review of Phenomenological Schottky Barrier Data.- 3. The Chemistry and Structure of the Interfacial Layer.- 3.1. Synopsis of the Layer-by-Layer Evolution.- 3.2. Some Techniques for Studying the Stages of Interface Formation.- 4. Evolution of the Interfacial Layer.- 4.1. Stage 0: The Clean Semiconductor Surface.- 4.1.1. Silicon (100) and (111) Surfaces.- 4.1.2. GaAs (110) and GaAs (100) Surfaces.- 4.2. Stage 1: The Dilute Limit (< 1/2 Monolayer).- 4.3. Stage 2: Monolayer Formation-Metal Film Nucleation.- 4.4. Stage 3: Additional Monolayers and Interdiffusion.- 4.5. Some Specific Characteristics of the Interfacial Layers.- 5. Formation of Interface States.- 5.1. Intrinsic Interface States Derived from the Metal and Semiconductor.- 5.2. Localized Defect and Impurity Related States.- 5.3. Interface States and the Stages of Interface Formation.- 6. Case Studies of the Chemistry and Structure of Schottky Barrier Formation.- 6.1. Case Studies of Silicon Schottky Barriers.- 6.1.1. Al, Ag, Cu, and Au Schottky Barriers.- 6.1.2. Silicide-Silicon Interfaces.- 6.2. Case Studies of III-V and II-VI Compound Semiconductor Schottky Barriers.- 6.2.1. The Ga-Al-As System.- 6.2.2. The GaAlAs Ternary System with Au Schottky Barriers.- 6.2.3. InP.- 6.2.4. Some II-VI Examples.- 7. Summary.- References.- 3. Fabrication and Characterization of Metal-Semiconductor Schottky Barrier Junctions.- 1. Introduction.- 2. Selection of Semiconductor Materials.- 3. Metal-Semiconductor Systems.- 3.1. Metal-Silicon Systems.- 3.2. Metal-GaAs Systems.- 3.3. Multilayer Metallization Systems.- 4. Design Considerations.- 5. Fabrication Technology.- 5.1. Surface Processing.- 5.2. Dielectric Film Deposition.- 5.3. Ohmic Contact Formation.- 5.4. Metal Deposition.- 5.5. Other Steps.- 6. Characterization.- References.- 4. Schottky-Barrier-Type Optoelectronic Structures.- 1. Introduction.- 2. Barrier Formation in Schottky-Barrier-Type Junctions.- 3. Transport in Schottky-Barrier-Type Structures.- 3.1. MS and MIS Structures.- 3.2. SIS Structures.- 4. Schottky-Barrier-Type Optoelectronic Structures.- 4.1. Schottky-Barrier-Type Light-Emitting Structures.- 4.2. Schottky-Barrier-Type Photodiodes.- 4.3. Schottky-Barrier-Type Photovoltaic Devices.- 4.3.1. MS and MIS Photovoltaic Devices.- 4.3.2. SIS Photovoltaic Devices.- 3. Summary.- References.- 5. Schottky Barrier Photodiodes.- 1. Introduction.- 2. General Parameters of Photodiodes.- 2.1. Signal-to-Noise Ratio (S/N).- 2.2. Noise Equivalent Power (NEP).- 2.3. Detectivity (D).- 2.4. Normalized Detectivity (D*).- 2.5. Detectivity Normalized Also with Respect to the Field of View(D**).- 2.6. Resistance Area Product.- 2.7. Response Time.- 3. Selection of Materials.- 3.1. Metal Systems.- 3.2. Semiconducting Materials.- 4. Fabrication Technology.- 5. Techniques for Evaluating Device Parameters.- 5.1. Current-Voltage Characteristics.- 5.2. Capacitance-Voltage Characteristics.- 5.3. Photoelectric Measurements.- 5.4. Electron Beam Induced Current Technique.- 6. Applications.- 7. Conclusions.- References.- 6. Microwave Schottky Barrier Diodes.- 1. Introduction.- 2. Diode Design Considerations.- 2.1. Equivalent Circuit.- 2.2. Frequency Conversion.- 2.3. Basic Mixer Diode RF Parameters.- 2.3.1. Conversion Loss Theory.- 2.3.2. Noise-Temperature Ratio.- 2.3.3. Overall Receiver Noise Figure.- 2.3.4. Mixer Noise Temperature.- 2.3.5. RF Impedance.- 2.3.6. IF Impedance.- 2.3.7. Receiver Sensitivity.- 2.3.8. Doppler Shift.- 2.3.9. Typical Doppler Radar System.- 2.4. Basic Detector RF Parameters.- 2.4.1. Video Resistance (Rv).- 2.4.2. Voltage Sensitivity.- 2.4.3. Current Sensitivity ?.- 2.4.4. Minimum Detectable Signal (MDS).- 2.4.5. Tangential Signal Sensitivity (TSS).- 2.4.6. Nominal Detectable Signal (NDS).- 2.4.7. Noise Equivalent Power (NEP).- 2.4.8. Video Bandwidth.- 2.4.9. Superheterodyne vs. Single Detection.- 2.5. Mixer Configurations.- 2.5.1. Single-Ended Mixer.- 2.5.2. Single-Balanced Mixer.- 2.5.3. Double-Balanced Mixer.- 2.5.4. Image Rejection Mixer.- 2.5.5. Image Enhanced or Image Recovery Mixer.- 3. Properties of Schottky Barrier Diodes.- 3.1. Diode Theory.- 3.2. DC Parameters.- 3.2.1. Junction Capacitance.- 3.2.2. Overlay Capacitance.- 3.2.3. Series Resistance.- 3.2.4. Figure of Merit.- 3.3. Semiconductor Materials.- 3.4. Epitaxial GaAs.- 3.5. Barrier Height Lowering.- 3.6. Fabrication.- 4. Microwave Performance.- 4.1. Mixer Diodes.- 4.2. Detector Diodes.- 5. RF Pulse and CW Burnout.- 5.1. Introduction.- 5.2. Factors Affecting RF Burnout.- 5.3. Experimental Results.- 5.4. Physical Analysis of RF Pulsed Silicon Schottky Barrier Failed Diodes.- 5.5. Physical Analysis of RF Pulsed Millimeter GaAs Schottky Barrier Failed Diodes.- 5.6. Electrostatic Failure of Silicon Schottky Barrier Diodes.- 6. Conclusions.- References.- 7. Metal-Semiconductor Field Effect Transistors.- 1. Introduction.- 2. Small-Signal FET Theory.- 3. Design Parameters of a Low-Noise Device.- 4. Practical Small-Signal FET Fabrication Techniques.- 4.1. Material Growth Techniques.- 4.2. FET Fabrication Technology.- 5. GaAs Power Field Effect Transistors.- 5.1. Principle of Power FET Operation.- 5.2. Thermal Impedance.- 5.3. Power FET Technology.- 6. Conclusions.- References.- 8. Schottky Barrier Gate Charge-Coupled Devices.- 1. Introduction.- 2. Schottky Gate CCDs.- 3. Potential-Charge Relationships.- 3.1. Surface Channel CCD.- 3.2. Bulk Channel CCD.- 3.3. Schottky Gate CCD.- 4. Charge Storage Capacity.- 4.1. Surface Channel CCD.- 4.2. Bulk Channel CCD.- 4.3. Schottky Gate CCD.- 5. Charge Transfer.- 5.1. Charge Transfer Efficiency.- 5.2. Charge Transfer Mechanisms.- 5.2.1. Surface Channel CCD.- 5.2.2. Bulk Channel CCD.- 5.2.3. Schottky Gate CCD.- 6. Input-Output Circuits.- 7. Schottky Gate Heterojunction CCDs.- 8. Experimental Results.- 8.1. High-Frequency Devices.- 8.2. Heterojunction Devices.- 9. Applications.- References.- 9. Schottky Barriers on Amorphous Si and their Applications.- 1. Introduction.- 2. Properties of Amorphous Si.- 2.1. Deposition Methods.- 2.2. Structural Properties.- 2.3. Electronic Properties.- 2.4. Surfaces.- 3. The Schottky Barrier on ?-Si:H.- 3.1. Current-Voltage Measurements.- 3.2. Capacitance Measurements.- 3.3 Internal Photoemission.- 4. Interface Kinetics and Its Effect on the Schottky Barrier.- 5. Applications.- 5.1. Drift Mobility.- 5.2. Deep Level Transient Spectroscopy.- 5.3. Solar Cells.- 5.4. Thin Film Transistors.- 6. Concluding Remarks.- References.

Colossal electroresistance in metal/ferroelectric/semiconductor tunnel diodes for resistive switching memories

Abstract: We propose a tunneling heterostructure by replacing one of the metal electrodes in a metal/ferroelectric/metal ferroelectric tunnel junction with a heavily doped semiconductor. In this metal/ferroelectric/semiconductor tunnel diode, both the height and the width of the tunneling barrier can be electrically modulated due to the ferroelectric field effect, leading to a colossal tunneling electroresistance. This idea is implemented in Pt/BaTiO3/Nb:SrTiO3 heterostructures, in which an ON/OFF conductance ratio above 10$^4$ can be readily achieved at room temperature. The colossal tunneling electroresistance, reliable switching reproducibility and long data retention observed in these ferroelectric tunnel diodes suggest their great potential in non-destructive readout nonvolatile memories.

Visible-Light Communications Using a CMOS-Controlled Micro-Light- Emitting-Diode Array

Abstract: We report the high-frequency modulation of individual pixels in 8 × 8 arrays of III-nitride-based micro-pixellated light-emitting diodes, where the pixels within the array range from 14 to 84 μ m in diameter. The peak emission wavelengths of the devices are 370, 405, 450 and 520 nm, respectively. Smaller area micro-LED pixels generally exhibit higher modulation bandwidths than their larger area counterparts, which is attributed to their ability to be driven at higher current densities. The highest optical -3 dB modulation bandwidths from these devices are shown to be in excess of 400 MHz, which, to our knowledge, are the highest bandwidths yet reported for GaN LEDs. These devices are also integrated with a complementary metal-oxide-semiconductor (CMOS) driver array chip, allowing for simple computer control of individual micro-LED pixels. The bandwidth of the integrated micro-LED/CMOS pixels is shown to be up to 185 MHz; data transmission at bit rates up to 512 Mbit/s is demonstrated using on-off keying non return-to-zero modulation with a bit-error ratio of less than 1 × 10-10, using a 450 nm-emitting 24 μm diameter CMOS-controlled micro-LED. As the CMOS chip allows for up to 16 independent data inputs, this device demonstrates the potential for multi-Gigabit/s parallel data transmission using CMOS-controlled micro-LEDs.

Time division modulation with average current regulation for independent control of arrays of light emitting diodes

Abstract: Method and computer-readable medium embodiments provide for sourcing current to a series of light-emitting diodes in a plurality of series of light-emitting diodes. A method comprises generating a current, sequentially and separately switching the current to each of the series of light-emitting diodes in the plurality of series of light-emitting diodes for a corresponding period of time, and predicting an output voltage across a selected series of light-emitting diodes using a plurality of parameters stored in a memory.

An optical temperature sensor based on the upconversion luminescence from Tm3+/Yb3+ codoped oxyfluoride glass ceramic

Abstract: An optical temperature sensor based on the upconversion luminescence of Tm3+ has been developed. Under a 980 nm diode laser excitation, the fluorescence intensity ratio (FIR) between 700 (Tm3+:3F2,3 → 3H6) and 800 nm (Tm3+:3H4 → 3H6) upconversion emissions from Tm3+/Yb3+ codoped oxyfluoride glass ceramic was studied as a function of temperature in the range of 293–703 K. The 3F2,3 and 3H4 states of Tm3+ are verified to be thermally coupled levels. By using FIR technique, the sensitivity for detecting temperature variations achieved here is better than previous reported rare earth ions fluorescence based temperature sensors. With the advantages of intense upconversion luminescence and absolutely separated 700 and 800 nm emission bands, the Tm3+/Yb3+ codoped oxyfluoride glass ceramic is a very promising candidate for accurate optical temperature sensors with much higher sensitivity and resolution.

Spin-Polarized Light-Emitting Diode Based on an Organic Bipolar Spin Valve

Abstract: The spin-polarized organic light-emitting diode (spin-OLED) has been a long-sought device within the field of organic spintronics. We designed, fabricated, and studied a spin-OLED with ferromagnetic electrodes that acts as a bipolar organic spin valve (OSV), based on a deuterated derivative of poly(phenylene-vinylene) with small hyperfine interaction. In the double-injection limit, the device shows ~1% spin valve magneto-electroluminescence (MEL) response, which follows the ferromagnetic electrode coercive fields and originates from the bipolar spin-polarized space charge–limited current. In stark contrast to the response properties of homopolar OSV devices, the MEL response in the double-injection device is practically independent of bias voltage, and its temperature dependence follows that of the ferromagnetic electrode magnetization. Our findings provide a pathway for organic displays controlled by external magnetic fields.

Rectification at Graphene-Semiconductor Interfaces: Zero-Gap Semiconductor-Based Diodes

Abstract: Diodes based on metal-semiconductor interfaces are common place in semiconductor electronics. What happens when the normal metal is replaced by monolayer graphene? A group of physicists at University of Florida experimentally demonstrate that graphene-semiconductor interfaces make interesting diodes for a surprisingly wide variety of semiconductors.

Low-Power Wireless Power Delivery

Abstract: This paper addresses design and implementation of integrated rectifier-antennas (rectennas) for wireless powering at low incident power densities, from 25 to 200 μW/cm2. Source-pull nonlinear measurement of the rectifying devices is compared to harmonic-balance simulations. Optimal diode RF and dc impedances for most efficient rectification, as a function of input power, are obtained. This allows optimized antenna design, which can eliminate or simplify matching networks and improve overall efficiency. As an example of the design methodology, Schottky diodes were characterized at 1.96 GHz and an antenna is matched to the optimal complex impedance for the most efficient rectifier. For incident power density range of interest, the optimal impedance is 137 + j149 Ω, with an RF to dc conversion efficiency of the rectifying circuit alone of 63% and total rectenna efficiency of 54%.

Room-Temperature Terahertz Detectors Based on Semiconductor Nanowire Field-Effect Transistors

Abstract: The growth of semiconductor nanowires (NWs) has recently opened new paths to silicon integration of device families such as light-emitting diodes, high-efficiency photovoltaics, or high-responsivity photodetectors. It is also offering a wealth of new approaches for the development of a future generation of nanoelectronic devices. Here we demonstrate that semiconductor nanowires can also be used as building blocks for the realization of high-sensitivity terahertz detectors based on a 1D field-effect transistor configuration. In order to take advantage of the low effective mass and high mobilities achievable in III–V compounds, we have used InAs nanowires, grown by vapor-phase epitaxy, and properly doped with selenium to control the charge density and to optimize source–drain and contact resistance. The detection mechanism exploits the nonlinearity of the transfer characteristics: the terahertz radiation field is fed at the gate-source electrodes with wide band antennas, and the rectified signal is then rea...

X-Band Reflectarray Antenna With Switching-Beam Using PIN Diodes and Gathered Elements

Abstract: An electronically switching-beam reflectarray antenna to be used in X-band has been designed, manufactured and tested, using PIN diodes as switching device. The antenna has 244 elements arranged in a circular aperture. With the aim of saving electronic devices and reducing both manufacturing complexity and cost, the phase control has been implemented at sub-array level, using aperture-coupled patches gathered by pairs to a common delay line. The antenna was designed to switch the beam between ±5°, in a scanning plane tilted 18.3° with respect to the YZ plane. Each state was obtained by forward biasing one half of the diodes, while the other half remains in reverse biasing. A third state with the beam pointing to 0° was obtained when all the diodes are in reverse biasing. The concept has been demonstrated by manufacturing and testing a breadboard. The measured radiation patterns fulfill the design requirements.

Controlling electron overflow in phosphor-free InGaN/GaN nanowire white light-emitting diodes.

Abstract: We have investigated for the first time the impact of electron overflow on the performance of nanowire light-emitting diodes (LEDs) operating in the entire visible spectral range, wherein intrinsic white light emission is achieved from self-organized InGaN quantum dots embedded in defect-free GaN nanowires on a single chip. Through detailed temperature-dependent electroluminescence and simulation studies, it is revealed that electron leakage out of the device active region is primarily responsible for efficiency degradation in such nanowire devices, which in conjunction with the presence of nonradiative surface recombination largely determines the unique emission characteristics of nanowire light-emitting diodes. We have further demonstrated that electron overflow in nanowire LEDs can be effectively prevented with the incorporation of a p-doped AlGaN electron blocking layer, leading to the achievement of phosphor-free white light-emitting diodes that can exhibit for the first time virtually zero efficiency droop for injection currents up to ~2200 A/cm(2). This study also provides unambiguous evidence that Auger recombination is not the primary mechanism responsible for efficiency droop in GaN-based nanowire light-emitting diodes.

Interplay of polarization fields and Auger recombination in the efficiency droop of nitride light-emitting diodes

Abstract: We use theoretical modeling to investigate the effect of polarization fields and non-radiative Auger recombination on the efficiency-droop and green-gap problems of polar and nonpolar nitride light-emitting diodes. The dependence of radiative and nonradiative recombination rates on electron-hole wave-function overlap is analyzed. Device designs that minimize the polarization fields lead to higher efficiency, not because the internal quantum efficiency is improved at a given carrier density but because they can be operated at a lower carrier density for a given current density.

Power semiconductor device

Abstract: The present invention relates to a power semiconductor device such as a diode and thyristor. In a semiconductor device such as a diode and thyristor having at least one pn junction between a pair of main surfaces, a first main electrode is formed on the surface of one of the main surfaces and a second main electrode is formed on the surface of the other one of the main surfaces. A semiconductor lattice defect is formed such that its lattice defect density increases gradually in the direction from the first main electrode to the second main electrode. Since the distribution of carrier density in the conduction state can be flattened according to the invention, the reverse recovery charge can be reduced substantially without causing the ON-state voltage to increase.

Light and pH Cooperative Nanofluidic Diode Using a Spiropyran-Functionalized Single Nanochannel

Abstract: An artificial nanofluidic diode system is prepared, mimicking the light-gated and pH-tunable ion channels that play an important role in life sciences. When UV light is off, the nanochannel is in the closed state, analogous to a resistance. Under UV light irradiation and at pH 7, the current flows from the tip to the base, analogous to a diode; at pH 3, the situation (and the diode) is reversed.

Fast-Switching GaN-Based Lateral Power Schottky Barrier Diodes With Low Onset Voltage and Strong Reverse Blocking

Abstract: GaN-based heterostructure lateral Schottky barrier diodes (SBDs) grown on n-SiC substrate are investigated in this letter. These SBDs own very low onset voltage VF = 0.43 V, high reverse blocking VBR >; 1000 V, very low capacitive charge of 0.213 nC/A, and a very fast recovery time of 10 ps. These unique qualities are achieved by combining lateral topology, GaN:C back-barrier epitaxial structure, fully recessed Schottky anode (φB = 0.43 eV), and slanted anode field plate in a robust and innovative process. Diode operation at elevated temperature up to 200 °C was also characterized.

Continuous-wave InAs/GaAs quantum-dot laser diodes monolithically grown on Si substrate with low threshold current densities.

Abstract: We report the first room-temperature continuous-wave operation of III-V quantum-dot laser diodes monolithically grown on a Si substrate. Long-wavelength InAs/GaAs quantum-dot structures were fabricated on Ge-on-Si substrates. Room-temperature lasing at a wavelength of 1.28 μm has been achieved with threshold current densities of 163 A/cm2 and 64.3 A/cm2 under continuous-wave and pulsed conditions for ridge-waveguide lasers with as cleaved facets, respectively. The value of 64.3 A/cm2 represents the lowest room-temperature threshold current density for any kind of laser on Si to date.

Analytic model for the efficiency droop in semiconductors with asymmetric carrier-transport properties based on drift-induced reduction of injection efficiency

Abstract: An analytic model is developed for the droop in the efficiency-versus-current curve for light-emitting diodes (LEDs) made from semiconductors having strong asymmetry in carrier concentration and mobility. For pn-junction diodes made of such semiconductors, the high-injection condition is generalized to include mobilities. Under high-injection conditions, electron drift in the p-type layer causes a reduction in injection efficiency. The drift-induced leakage term is shown to have a 3rd and 4th power dependence on the carrier concentration in the active region; the values of the 3rd- and 4th-order coefficients are derived. The model is suited to explain experimental efficiency-versus-current curves of LEDs. V C 2012 American Institute of Physics .[ http://dx.doi.org/10.1063/1.4704366]

Engineering the current-voltage characteristics of metal-insulator-metal diodes using double-insulator tunnel barriers

Abstract: The femtosecond-fast transport in metal–insulator–metal (MIM) tunnel diodes makes them attractive for applications such as ultra-high frequency rectenna detectors and solar cells, and mixers. These applications impose severe requirements on the diode current–voltage I ( V ) characteristics. For example, rectennas operating at terahertz or higher frequencies require diodes to have low resistance and adequate nonlinearity. To analyze and design MIM diodes with the desired characteristics, we developed a simulator based on the transfer-matrix method, and verified its accuracy by comparing simulated I ( V ) characteristics with those measured in MIM diodes that we fabricated by sputtering, and also with simulations based on the quantum transmitting boundary method. Single-insulator low-resistance diodes are not sufficiently nonlinear for efficient rectennas. Multi-insulator diodes can be engineered to provide both low resistance and substantial nonlinearity. The improved performance of multi-insulator diodes can result from either resonant tunneling or a step change in tunneling distance with voltage, either of which can be made to dominate by the appropriate choice of insulators and barrier thicknesses. The stability of the interfaces in the MIIM diodes is confirmed through a thermodynamic analysis.

Suppression of electron overflow and efficiency droop in N-polar GaN green light emitting diodes

Abstract: In this letter, we experimentally demonstrate direct correlation between efficiency droop and carrier overflow in InGaN/GaN green light emitting diodes (LEDs). Further, we demonstrate flat external quantum efficiency curve up to 400 A/cm2 in a plasma assisted molecular beam epitaxy grown N-polar double quantum well LED without electron blocking layers. This is achieved by exploring the superior properties of reverse polarization field of N-face polarity, such as effective carrier injection and higher potential barriers against carrier overflow mechanism. The LEDs were found to operate with a low (∼2.3 V) turn-on voltage.

Thermal resistance reduction in high power superluminescent diodes by using active multi-mode interferometer

Abstract: Low thermal resistance of high power superluminescent diodes (SLEDs) by using active multi-mode interferometer (active-MMI) is presented in this paper. The active layer temperature evaluation demonstrates that the power saturation mechanism in active-MMI SLED is heat for the first time. Low thermal resistance of 4.83 K/W in active-MMI SLEDs leads to a high power of 115 mW. Moreover, the effect of the active area size on the output power is demonstrated both experimentally and theoretically. Good agreement between the theoretical and experimental results indicates that active-MMI configuration is a new design in support of efficient heat dissipation and thermal resistance reduction for SLEDs.

Back-to-back Schottky diodes: the generalization of the diode theory in analysis and extraction of electrical parameters of nanodevices

Abstract: We report on the analysis of nonlinear current?voltage characteristics exhibited by a set of blocking metal/SnO2/metal. Schottky barrier heights in both interfaces were independently extracted and their dependence on the metal work function was analyzed. The disorder-induced interface states effectively pinned the Fermi level at the SnO2 surface, leading to the observed Schottky barriers. The model is useful for any two-terminal device which cannot be described by a conventional diode configuration.

A review of developments in near infrared methane detection based on tunable diode laser

Abstract: Diode laser based absorption spectroscopy (DLAS) is widely used for gas detection in variety of applications across the energy, petrochemical and mining industries. Recent developments in near and mid infrared diode lasers have improved the sensitivity of gas measurement based on high resolution spectra of target species. The availability of near-infrared diodes that can operate at room temperature has expanded the application of spectroscopy technique in hand-held gas detection devices. DLAS in conjunction with optical fibres has also been applied for the distributed sensing and monitoring of various gases in real-time basis. This paper, after introducing methane characteristics and semiconductor diode lasers, comprehensively reviews development in spectroscopic methane sensing techniques in accordance with methane absorption lines in the near infrared spectrum.

1.1-Gb/s White-LED-Based Visible Light Communication Employing Carrier-Less Amplitude and Phase Modulation

Abstract: We demonstrate 1.1-Gb/s visible light communication (VLC) employing carrier-less amplitude and phase modulation (CAP) and a commercially available phosphorescent white light emitting diode (LED). Optical blue filtering, precompensation, and decision feedback equalization are used to compensate the frequency response of the phosphor-based white LED. Various modulation orders of CAP signals are investigated to maximize the capacity of the VLC system. The record data rate of 1.1 Gb/s with the bit error rate performance below the FEC limit of 10-3 is successfully achieved >; 23-cm air-transmission via a 220-MBaud 32-CAP signal.

Light-emitting diode

Abstract: The invention discloses a light-emitting diode, comprising a semiconductor substrate with a first conduction type, an active layer on the surface of the semiconductor substrate and a semiconductor covering layer provided with the active layer surface and a second conduction layer, wherein an electrode is arranged on one surface, opposite to the active layer, of the semiconductor covering layer and comprises a graphene layer and a metal layer, and the graphene layer is arranged between the metal layer and the semiconductor covering layer to improve ohmic contact between the metal layer and semiconductor materials. The light-emitting diode has the advantage that through inserting the graphene layer, the surface electronic state of the semiconductor materials can be changed greatly without a process of annealing or etching and the like, thereby reducing contact barrier between any metal or alloy and a semiconductor.

Performance tradeoff between lateral and interdigitated doping patterns for high speed carrier-depletion based silicon modulators

Abstract: Carrier-depletion based silicon modulators with lateral and interdigitated PN junctions are compared systematically on the same fabrication platform. The interdigitated diode is shown to outperform the lateral diode in achieving a low VπLπ of 0.62 V∙cm with comparable propagation loss at the expense of a higher depletion capacitance. The low VπLπ of the interdigitated PN junction is employed to demonstrate 10 Gbit/s modulation with 7.5 dB extinction ration from a 500 µm long device whose static insertion loss is 2.8 dB. In addition, up to 40 Gbit/s modulation is demonstrated for a 3 mm long device comprising a lateral diode and a co-designed traveling wave electrode.

Practical Design and Implementation Procedure of an Interleaved Boost Converter Using SiC Diodes for PV Applications

Abstract: The implementation of an interleaved boost converter (IBC) using SiC diodes for photovoltaic (PV) applications is presented in this paper. The converter consists of two switching cells sharing the PV panel output current. Their switching patterns are synchronized with 180° phase shift. Each switching cell has a SiC Schottky diode and a CoolMOS switching device. The SiC diodes provide zero reverse-recovery current ideally, which reduces the commutation losses of the switches. Such an advantage from the SiC diodes enables higher efficiency and higher power density of the converter system by reducing the requirement of the cooling system. This paper presents also an optimization study of the size and efficiency of the IBC. Based on 1) the steady-state characteristic of the topology; 2) the static and dynamic characteristics of the switching cells; 3) the loss model of the magnetic components; and 4) the cooling system design, the paper provides a set of design criteria, procedures, and experimental results for a 2.5 kW IBC prototype using SiC diodes.