Reverse Biased Diode Research Articles

A NOVEL DUAL-BAND RECONFIGURABLE SQUARE-RING MICROSTRIP ANTENNA

A novel compact dual-band reconfigurable square-ring microstrip antenna is presented. The tuning is achieved using a single varactor diode connected to a small square patch attached to an inner corner of the square-ring. The square patch perturbs the symmetry and splits the two degenerate modes to create dual-band operation. The frequency ratio in the range of 1.04 to 1.4 can be achieved by the proper selection of the square patch size. The lower resonance frequency can be further decreased by loading the square patch at its corner by a reverse biased varactor diode. The diode has almost no effect on the upper resonance frequency. This technique is used to implement an electronically tunable dual-band antenna on FR4 material with er =4 .5 and 1.5 mm thickness. The size of the ring,the square patch,and the varactor used,are selected to yield a fixed upper resonance frequency at about 1.93 GHz. The resulting lower resonance frequency is tuned from 1.37 to 1.7 GHz in the voltage range from 0 to 30 V,respectively. The measurements agree well with simulation results.

Dual-Band Electronically Switchable Shorted Patch Antenna

An improved design of a shorted patch antenna with electronic switching of the operating bands is proposed. PIN diodes are used as switches for connecting four shorting posts to the ground plane. With reverse biased diodes the antenna operates at 2 GHz, while with forward biased diodes the operating frequency is 4 GHz. Two electronically switched impedance matching networks are designed, one for each band. The impedance matching networks are electronically switched with the same bias voltage used for switching the patch resonant frequency. The E- and H-plane co-polarization and cross-polarization radiation patterns are measured in both bands. The results show good radiation characteristics and lower cross-polarization levels in comparison to previous designs.

Raman-based silicon photonics

This paper reviews recent progress in a new branch of silicon photonics that exploits Raman scattering as a practical and elegant approach for realizing active photonic devices in pure silicon. The large Raman gain in the material, enhanced by the tight optical confinement in Si/SiO2 heterostructures, has enabled the demonstration of the first optical amplifiers and lasers in silicon. Wavelength conversion, between the technologically important wavelength bands of 1300 and 1500 nm, has also been demonstrated through Raman four wave mixing. Since carrier generation through two photon absorption is omnipresent in semiconductors, carrier lifetime is the single most important parameter affecting the performance of silicon Raman devices. A desired reduction in lifetime is attained by reducing the lateral dimensions of the optical waveguide, and by actively removing the carriers with a reverse biased diode. An integrated diode also offers the ability to electrically modulate the optical gain, a unique property not available in fiber Raman devices. Germanium-silicon alloys and superlattices offer the possibility of engineering the otherwise rigid spectrum of Raman in silicon.

Simulation Results on Submillimeter Wave Detection by Josephson Fluxonic Diode and a Method to Address Its Focal Plane Array

Application of radiation to a reverse-biased Josephson fluxonic diode (JFD) creates vortex-antivortex pairs. Pairs are created at each peak of sinusoidal radiation and move under the application of the bias current, exhibiting a voltage which depends on the frequency of incoming radiation. Simulation results for frequencies ranging from 50 to 700 GHz have been obtained. A simple and practical addressing scheme is proposed for a matrix of JFD pixels. Ease of fabrication, inherent gain, simultaneous determination of amplitude and frequency of radiation, large output current, and simple addressability in focal plane arrays are among the advantages of JFD as a direct submillimeter wave detector

Electrolyte diodes with weak acids and bases. I. Theory and an approximate analytical solution

Until now acid-base diodes and transistors applied strong mineral acids and bases exclusively. In this work properties of electrolyte diodes with weak electrolytes are studied and compared with those of diodes with strong ones to show the advantages of weak acids and bases in these applications. The theoretical model is a one dimensional piece of gel containing fixed ionizable groups and connecting reservoirs of an acid and a base. The electric current flowing through the gel is measured as a function of the applied voltage. The steady-state current-voltage characteristic (CVC) of such a gel looks like that of a diode under these conditions. Results of our theoretical, numerical, and experimental investigations are reported in two parts. In this first, theoretical part governing equations necessary to calculate the steady-state CVC of a reverse-biased electrolyte diode are presented together with an approximate analytical solution of this reaction-diffusion-ionic migration problem. The applied approximations are quasielectroneutrality and quasiequilibrium. It is shown that the gel can be divided into an alkaline and an acidic zone separated by a middle weakly acidic region. As a further approximation it is assumed that the ionization of the fixed acidic groups is complete in the alkaline zone and that it is completely suppressed in the acidic one. The general solution given here describes the CVC and the potential and ionic concentration profiles of diodes applying either strong or weak electrolytes. It is proven that previous formulas valid for a strong acid-strong base diode can be regarded as a special case of the more general formulas presented here.

Electrolyte diodes with weak acids and bases. II. Numerical model calculations and experiments

This is the second part of our work dealing with electrolyte diodes with weak acids and bases. In the first part an approximative analytical solution was derived for the steady-state current-voltage characteristic (CVC) of a reverse-biased diode (a quasi-one-dimensional gel connecting an acidic and an alkaline reservoir), applying either strong or weak electrolytes. An approximative analytical solution is compared here with a numerical solution free of any approximations and with CVCs measured experimentally with both strong and weak electrolytes. It is shown that the deviations between the numerical and analytical solutions are mostly due to assumptions made for the fixed charge concentration profiles. The concept of optimal analytical solution is introduced which does not use such assumptions and applies only the quasielectroneutrality and quasiequilibrium approximations. It is proven that the slope of the CVC based on the optimum analytical solution can be calculated without the complicated derivation of that solution itself. The calculation of that slope is based on the fact that in the optimum analytical solution all currents are inversely proportional to the length if the boundary conditions are held constant and realizing that in the middle part of the gel the only mobile counterions of the fixed ionized groups are hydrogen ions. In the experimental part the apparatus and the preparation of the gel are described together with the CVCs measured with strong and weak electrolytes. From these CVCs the fixed ion concentration in the middle part of the gel can be determined. That fixed ion concentration is 1.96 x 10(-4)M measured with weak electrolytes and 3.48 x 10(-4)M measured with strong electrolytes. The deviation indicates that the strong base causes some hydrolysis of the gel. Finally, possible applications of weak acid-weak base diodes are discussed.

Large-signal diode modeling-an alternative parameter-extraction technique

An alternative numerical optimization method of large-signal equivalent-circuit diode modeling using dc and small-signal S-parameter measurements is described. In general, there are two ways to extract the equivalent-circuit parameters to model a nonlinear device such as a diode. They are based on numerical optimization or noniterative analytical procedure. The former is usually better in approximating the device response. Nevertheless, it requires arbitrary selection of a voltage-dependent S-parameter set to obtain the voltage-independent parameters. In this alternative numerical optimization method, an arbitrary selection of a voltage-dependent S-parameter set to obtain the voltage-independent parameters is not required. Validation of this parameter-extraction technique is done via modeling a forward-biased tunnel diode and a reverse-biased varactor diode. The models are further verified by implementing them in designing and developing an oscillator and a voltage-controlled oscillator.

Soliton transistor

An all soliton transistor is introduced which uses a train of soliton-like vortices inside long Josephson junctions to turn off the movement of another train of vortices. In our practical realization, a long Josephson junction injects vortices into a reverse-biased Josephson fluxonic diode, corresponding to the ON state of the transistor. Injecting antivortices through a third long junction annihilates vortices before they could reach the Josephson fluxonic diode. This corresponds to the OFF state. Experimental results on the successful operation of this transistor as a NOT gate are provided.

Observed trapping of minority-carrier electrons in p-type GaAsN during deep-level transient spectroscopy measurement

Deep-level transient spectroscopy measurements on a reverse-biased p-type GaAsN Schottky diode grown by metalorganic chemical vapor deposition show a minority-carrier trap signal corresponding to an electron trap having an activation energy of about 0.2eV. The proportion of trapped electrons agrees with that of modeled defect states near the Schottky-barrier metal interface whose occupation is affected by changing reverse-bias conditions. Estimates of thermionic emission provide adequate filling of the traps with electrons from the metal. The inclusion of a GaAs layer between the metal and GaAsN layer reduces the electron-trapping signal.

Characterization of Er/O-doped Si-LEDs with Low Thermal Quenching

AbstractElectroluminescence studies of MBE-grown Er/O-doped Si-diodes at reverse bias have been done. For some devices there is much reduced thermal quenching of the emission at 1.54 νm. There are examples where the temperature dependence is abnormal in that the intensity for a constant current even increases with temperature up to e.g. 80 °C. These devices have been studied with cross-sectional transmission electron microscopy to see the microstructure of the Er/O-doped layers as well as the B-doped SiGe-layers that are used as electron emitters during reverse bias. Although there are defects in the layers there is no evidence for large thick precipitates of SiO2. While reduced thermal quenching often is attributed to having the Er-ions within SiO2 layers, this is not the case for our structures as evidenced by our TEM-studies. The origin of the abnormal temperature dependence is attributed to the two mechanisms of breakdown in the reverse-biased diodes. At low temperature the breakdown current is mainly due to avalanche resulting in low-energy electrons and holes that quenches the intensity by Auger deexcitation of the Er-ions. At higher temperature the breakdown current is mainly phonon-assisted tunneling which results in a more efficient pumping with less de-excitation of the Er-ions. Finally at the highest temperatures the thermal quenching sets in corresponding to an activation energy of 125 meV, which is slightly lower than 150 meV that has been reported in other studies.

Non-degenerate fs pump-probe study on InGaN with multi-wavelength second-harmonic generation

Non-degenerate fs pump-probe experiments in the UV-visible range for ultrafast carrier dynamics study of InGaN with adjustable pump and probe photon energies are implemented with simultaneously multiwavelength second-harmonic generation (SHG) of a 10 fs Ti:sapphire laser. The multi-wavelength SHG is realized with two beta-barium borate crystals of different cutting angles. The full-widths at half-maximum of the SHG pulses are around 150 fs, which are obtained from the cross-correlation measurement with a reverse-biased 280-nm light-emitting diode as the twophoton absorption photo-detector. Such pulses are used to perform nondegenerate pump-probe experiments on an InGaN thin film, in which indium-rich nano-clusters and compositional fluctuations have been identified. Relaxation of carriers from the pump level to the probe one through the scattering-induced local thermalization (<1 ps) and then the carrier-transport-dominating global thermalization (in several ps) processes is observed.

Measurement of Micrometer Diffusion Lengths by Nuclear Spectrometry

A method for determination of diffusion lengths in the range 0.5-50 µm, which corresponds to carrier lifetimes in the nanosecond range, is suggested A calibrated nonequilibrium charge is injected into the base of the reverse-biased diode structure. The injection is provided by alpha particles generated by natural decay in the single-particle counting mode. The nuclear spectrometry technique is used to measure the amount of charge that diffused across the base to the boundary of the electric-field region. The loss of charge during the diffusion is calculated as a function of the depth of alpha particle penetration beyond the electric-field region. The derived power-law functions make it possible to relate the diffusion length with the exponent and numerical factor that describes the loss of charge. The experiment is performed with lightly doped 4H-SiC epitaxial films. © 2005 Pleiades Publishing, Inc.

Displacement damage-induced catastrophic second breakdown in silicon carbide Schottky power diodes

A novel catastrophic breakdown mode in reverse biased silicon carbide diodes has been seen for particles that are too low in LET to induce SEB, however SEB-like events were seen from particles of higher LET. The low LET breakdown mechanism correlates with second breakdown in diodes due to increased leakage and assisted charge injection from incident particles. Percolation theory was used to predict some basic responses of the devices.

Ultrabroadband Emission Spectrum from a Reverse-Biased 4H-SiC p–n Junction Diode

We measured the light-emission spectrum from a reverse-biased 4H-SiC p–n junction diode under the avalanche condition. The diode was fabricated with the edge of the mesa being negatively beveled. Avalanche breakdown occurred at the periphery where the p–n junction intercepted the surface. As a result, the emission showed a broadband spectrum containing ultraviolet, visible, and near-infrared regions. This is the first observation of the ultraviolet emission from a reverse-biased SiC diode.

A predistortion linearizer using a tunable resonator

In this letter, a novel predistortion topology using a tunable resonator is presented. The core of the circuit is a series tunable resonator employing a reverse biased varactor diode. The junction capacitance of the varactor diode increases with RF input power, effectively shifting the resonant frequency of the circuit. This results in the amplitude and phase deviations at the frequency of operation. A 1.8-GHz power amplifier (PA), with a gain of 9 dB and 21-dBm output power, is linearized based on this technique. A maximum of 11 dB improvement in adjacent channel power ratio and an increase in 1.8 dB for the compression point is measured for the linearized PA.

TLP analysis of 0.125 μm CMOS ESD input protection circuit

In this investigation, TLP ESD analysis shows that if a large input resistor is used in combination with a secondary ggNMOS clamp in the input protection circuitry, then the trigger voltage, V t1, of the ggNMOS clamp is not a constant. The value is influenced by the size and properties of the input resistor, by current injection problems due to parallel resistive networks formed between the primary and secondary ESD circuits, by reverse bias diode leakage currents effects, and by source elevation effects due to voltage rises along the ESD ground bus.

Double electron drift device as a magnetic field sensor

A new magnetic field sensor based on electron transport in the depletion region of reverse-biased silicon pin diodes is presented. Its field sensitivity is derived from transport equations with magnetic fields. The new sensor consists of a pin diode across the silicon wafer, an injection line within the anode, and opposite to this line a gap, which splits the cathode into two halves. The fabrication of the pin diodes is compatible with CMOS technology. The fabrication required layer processing on both wafer sides, transfer of alignment markers from one side to the other. Magnetic measurements revealed the following main results: the magnetic field sensitivity was 1.6 T−1, i.e. 23 times larger than that of Hall probes. All measured field sensitivities were in accordance with theoretical predictions. At high injection currents a reduction of the field sensitivity is observed which is caused by beam broadening due to space charge effects. Due to the alignment accuracy of less than ±1 μm magnetic offsets of up to 0.05 T were observed.

Double electron drift device as a magnetic field sensor

A new magnetic field sensor based on electron transport in the depletion region of reverse-biased silicon pin diodes is presented. Its field sensitivity is derived from transport equations with magnetic fields. The new sensor consists of a pin diode across the silicon wafer, an injection line within the anode, and opposite to this line a gap, which splits the cathode into two halves. The fabrication of the pin diodes is compatible with CMOS technology. The fabrication required layer processing on both wafer sides, transfer of alignment markers from one side to the other. Magnetic measurements revealed the following main results: the magnetic field sensitivity was 1.6 T −1, i.e. 23 times larger than that of Hall probes. All measured field sensitivities were in accordance with theoretical predictions. At high injection currents a reduction of the field sensitivity is observed which is caused by beam broadening due to space charge effects. Due to the alignment accuracy of less than ±1 μm magnetic offsets of up to 0.05 T were observed.

Physical Device Modeling of a Varactor Diode

Starting with the recipe for the fabrication process of a silicon p-n junction varactor diode, the semiconductor device equations are solved using the finite-element method. The capacitance of the reverse biased diode is extracted using the junction depletion width which is quantified by introducing a depletion factor. Validation of the complete modeling process is achieved by fabricating the diode, mounting it on a microwave circuit and comparing experimental scattering parameter data with those predicted by a circuit simulator with the imported physical model.

Observing a p-n Junction in a Reverse-Biased GaP Light-Emitting Diode by Combining Electron Holography and Focused-Ion-Beam Milling

Observing a p-n Junction in a Reverse-Biased GaP Light-Emitting Diode by Combining Electron Holography and Focused-Ion-Beam Milling