Reverse Biased Diode Research Articles

Negative Gate Transconductance in MIS Tunnel Diode Induced by Peripheral Minority Carrier Control Mechanism

Negative Gate Transconductance (NGT) in the tunneling current of a metal-insulator-semiconductor (MIS) tunnel diode gated by an MIS tunnel gate capacitor is demonstrated in this work. The mechanism is that the effective Schottky barrier height of the MIS tunnel diode can be modulated by controlling the substrate surface minority carriers concentration with the gate bias of the MIS tunnel gate capacitor. Since the tunneling current of a reverse biased MIS tunnel diode is exponentially dependent on the effective Schottky barrier height, the signal of the rise and fall of minority carriers concentration can be read out by the tunneling current and therefore an NGT behavior appears.

Modelling of current-voltage characteristics of infrared photo-detectors based on type – II InAs/GaSb super-lattice diodes with unipolar blocking layers

It is shown that current-voltage characteristics of infrared photo-detectors based on type-II InAs/GaSb super-lattices with uni-polar blocking layers can be modelled similar to a junction diode with a finite series resistance on account of blocking barriers. As an example this paper presents the results of a study of current-voltage characteristics of a type II InAs/GaSb super-lattice diode with PbIbN architecture using a recently proposed [J. Appl. Phys. 116, 084502 (2014)] method for modelling of illuminated photovoltaic detectors. The thermal diffusion, generation – recombination (g-r), and ohmic currents are found as principal components besides a component of photocurrent due to background illumination. The experimentally observed reverse bias diode current in excess of thermal current (diffusion + g-r), photo-current and ohmic shunt current is reported to be best described by an exponential function of the type, Iexcess = Ir0 + K1exp(K2 V), where Ir0, K1 and K2 are fitting parameters and V is the applied bias voltage. The present investigations suggest that the exponential growth of excess current with the applied bias voltage may be taking place along the localized regions in the diode. These localized regions are the shunt resistance paths on account of the surface leakage currents and/or defects and dislocations in the base of the diode.

Leakage Current Mechanisms in Reverse Biased High-Voltage 4H-SiC Power Diodes

Today’s commercial 4H-SiC power diodes contain an abundance of threading screw dislocations (TSDs) and threading edge dislocations (TEDs). It is not clear exactly how these crystal defects manifest on the performance and reliability of high-voltage power devices. In this paper, extensive current-voltage (I-V) and capacitance-voltage (C-V) measurements of 600V, 1200V and 1700V commercial SiC power diodes at temperatures ranging from 22ºC to 250ºC will be reported. Detailed analysis of leakage current mechanisms is performed and it is shown that space charge limited current (SCLC) is a significant contributor to diode leakage current especially at increased electric fields. The static I-V data will be correlated with defect delineation using in-situ hard X-rays and it is shown that TSDs get excited first under high field stress conditions.

TCAD simulation for alpha-particle spectroscopy using SIC Schottky diode.

There is a growing requirement of alpha spectroscopy in the fields context of environmental radioactive contamination, nuclear waste management, site decommissioning and decontamination. Although silicon-based alpha-particle detection technology is mature, high leakage current, low displacement threshold and radiation hardness limits the operation of the detector in harsh environments. Silicon carbide (SiC) is considered to be excellent material for radiation detection application due to its high band gap, high displacement threshold and high thermal conductivity. In this report, an alpha-particle-induced electron-hole pair generation model for a reverse-biased n-type SiC Schottky diode has been proposed and verified using technology computer aided design (TCAD) simulations. First, the forward-biased I-V characteristics were studied to determine the diode ideality factor and compared with published experimental data. The ideality factor was found to be in the range of 1.4-1.7 for a corresponding temperature range of 300-500 K. Next, the energy-dependent, alpha-particle-induced EHP generation model parameters were optimised using transport of ions in matter (TRIM) simulation. Finally, the transient pulses generated due to alpha-particle bombardment were analysed for (1) different diode temperatures (300-500 K), (2) different incident alpha-particle energies (1-5 MeV), (3) different reverse bias voltages of the 4H-SiC-based Schottky diode (-50 to -250 V) and (4) different angles of incidence of the alpha particle (0°-70°).The above model can be extended to other (wide band-gap semiconductor) device technologies useful for radiation-sensing application.

Highly sensitive optically controlled tunable capacitor and photodetector based on a metal-insulator-semiconductor on silicon-on-insulator substrates

We describe a new type of optically sensitive tunable capacitor with a wide band response ranging from the ultraviolet (245 nm) to the near infrared (880 nm). It is based on a planar Metal-Oxide-Semiconductor (MOS) structure fabricated on an insulator on silicon substrate where the insulator layer comprises a double layer dielectric stack of SiO2-HfO2. Two operating configurations have been examined, a single diode and a pair of back-to-back connected devices, where either one or both diodes are illuminated. The varactors exhibit, in all cases, very large sensitivities to illumination. Near zero bias, the capacitance dependence on illumination intensity is sub linear and otherwise it is nearly linear. In the back-to-back connected configuration, the reverse biased diode acts as a light tunable resistor whose value affects strongly the capacitance of the second, forward biased, diode and vice versa. The proposed device is superior to other optical varactors in its large sensitivity to illumination in a very broad wavelength range (245 nm–880 nm), the strong capacitance dependence on voltage and the superior current photo responsivity. Above and beyond that structure requires a very simple fabrication process which is CMOS compatible.

Circuital modelling of S-shape removal in the current–voltage characteristic of TiOx inverted organic solar cells through white-light soaking

In this work light activation phenomenon in inverted bulk heterojunction (BHJ) organic solar cells (OSC) has been electrically modelled with a two-diode equivalent circuit. OSC are based on poly(3-hexylthiophene) (P3HT): 1-(3-methoxycarbonyl)-propyl-1-1-phenyl-(6,6) C61 (PCBM) with a titanium oxide (TiOx) sublayer. Current–voltage (I–V) characteristics show a highly pronounced S-shape that is gradually removed during light activation process. The circuit used to model I–V curves includes two diodes in forward and reverse bias together with two parallel resistances, RP1 and RP2. The parallel of the reverse bias diode and its corresponding resistance RP2 models the electrical behaviour of the TiOx interlayer. This interlayer has been thermally treated at different temperatures, from 80°C up to 180°C, reducing the activation time from 400s for unbaked devices down to 30s for devices annealed at temperatures higher than 80°C. The S-shape shown in the I–V characteristic is completely removed after a few minutes of white-light illumination. I–V curves recorded during the activation process have been fitted with the analytical solution of the two-diode circuit based on W-Lambert function. A decrease of the subcircuit 2 equivalent resistance has been found to be the cause of S-shape removal. This resistance diminishing is in good agreement with the increase of TiOx conductance with baking temperature and white-light exposure time found by other authors.

A new approach to investigate leakage current mechanisms in infrared photodiodes from illuminated current-voltage characteristics

This paper presents a new approach to investigate leakage current mechanisms in infrared photodiodes from the illuminated current–voltage characteristics. The example of mid-wave mercury cadmium telluride photodiodes is presented to illustrate the new approach. The new method is suitable for evaluating diodes in an array environment as advance knowledge of any of the material or device parameters are not required. The thermal saturation current is estimated from the observed open circuit voltage and zero-bias current (photo-current) of the diode. The ohmic shunt resistance is estimated from the observed maximum dynamic impedance of the diode. The experimentally observed reverse bias diode current in excess of thermal current, photo-current, and ohmic shunt current is reported to be best described by an exponential function of the type, Iexcess = Ir0 + K1 exp (K2 V), where Ir0, K1, and K2 are fitting parameters and V is the applied bias voltage. Our investigations reveal a close link between the excess current and the sources of ohmic currents in the diode. Exponential growth of excess current with the applied bias voltage has been interpreted as an indication of soft breakdown of the diodes.

Capacitance-voltage profiling: Research-grade approach versus low-cost alternatives

We describe an experiment that implements capacitance-voltage profiling on a reverse-biased Schottky barrier diode to determine the density of impurity dopants in its semiconductor layer as well as its built-in electric potential. Our sample is a commercially produced Schottky diode. Three different experimental setups, one using research-grade instrumentation, the other two using low-cost alternatives, are given and their results compared. In each of the low-cost setups, phase-sensitive detection required to measure the sample's capacitance is carried out using an inexpensive data acquisition (DAQ) device and a software program that implements a lock-in detection algorithm. The limitations of the DAQ device being used (e.g., restricted analog-to-digital conversion speed, inadequate waveform generation capabilities, lack of hardware triggering) are taken into account in each setup. Excellent agreement for the value of the doping density obtained by the all three setups is found and this value is shown to be consistent with the result of an independent method (secondary ion mass spectroscopy).

Effects of High Electric Fields on the Magnitudes of Current Steps Produced by Single Particle Displacement Damage

Measurements of single particle displacement damage are presented as discrete increases in reverse-biased diode leakage current, or current steps, caused by individual heavy ions in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">252</sup> Cf-irradiated JFET diodes. The maximum size of measured current steps agrees with calculations obtained from the expression for Shockley-Read-Hall generation when the radiation-induced defect density is derived from Monte Carlo simulations of atomic displacements and the electric field enhancement of defect emission is taken into account. The distribution of the current steps shows good agreement with experimental data.

Study of unidirectional conductivity on the electrical discharge machining of semiconductor crystals

Abstract This paper investigates the unidirectional conductivity of semiconductor crystals machined by electrical discharge machining (EDM) by analyzing the properties of current–voltage (I–V) curves of the equivalent circuit. The simplified equivalent circuit of a semiconductor EDM consists of reverse-biased diodes and linear resistance. The I–V curve has three typical parameters, namely, conduction angle, breakdown angle, and breakdown point. The values of the conduction angle and the breakdown point are determined by the contact area of the reverse-biased diode, and the breakdown angle is determined by the value of linear resistance. Two diodes exist in the model with two metal electric feeders. To increase the current in this model, the diode with larger contact area should be reverse-biased. If the work piece is connected to anode in semiconductor EDM, the diode in the conduction side is reverse-biased and the avalanche voltage is only 42 V. If the work piece is connected to the cathode in semiconductor EDM, then the arc plasma, which is a termination with a small area, becomes reverse-biased. The temperature in the arc plasma side is high, causing the breakdown voltage to be much higher than the theoretical calculation value 88.5 V. As a result, when the work piece is connected to the cathode, spark production is difficult. Holes are bored on the P-type semiconductor crystals by positive and negative polarity, which could prove that machining with positive polarity is suitable for P-type semiconductor crystals during EDM. When the no-load voltage is set to 150 V, the penetration speed by positive polarity can reach 533 μm/min.

High Area-Efficient ESD Clamp Circuit With Equivalent $RC$-Based Detection Mechanism in a 65-nm CMOS Process

A power-rail electrostatic discharge (ESD) clamp circuit realized with ESD clamp device drawn in the layout style of big field-effect transistor (BigFET), and with parasitic diode of BigFET as a part of ESD-transient detection mechanism, is proposed and verified in a 65-nm 1.2-V CMOS process. Skillfully utilizing the diode-connected MOS transistor as the equivalent large resistor and the parasitic reverse-biased diodes of BigFET as the equivalent capacitors, the new <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</i> -based ESD-transient detection mechanism can be achieved without using an actual resistor and capacitor to significantly reduce the layout area by ~82%, as compared to the traditional <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</i> -based ESD-transient detection circuit. From the measured results, the new proposed power-rail ESD clamp circuit with body effect of ESD clamp device can perform adjustable holding voltage under the ESD stress condition, as well as better immunity against mistrigger and transient-induced latch-on under fast power-on and transient noise conditions.

Influence of photocarriers to silicon optical modulator based on reverse-biased pn diode at 1550 nm wavelength

Theoretical analysis predicts that the performance of a silicon optical modulator based on carrier depletion in a reverse-biased pn diode is obviously influenced by photocarriers at 1550nm wavelength. Experimental results testify that the initial output optical power reduces by 1.2dB, and the extinction ratio decreases from 15.8dB to13.8dB due to the influence of photocarriers. Finally, a simple and feasible method to alleviate this influence by shorting the electrodes of the unmodulated phase shifter is proposed.

Analysis of contact effects in fully printed p-channel organic thin film transistors

Contact effects have been analyzed in fully printed p-channel OTFTs based on a pentacene derivative as organic semiconductor and with Au source–drain contacts. In these devices, contact effects lead to an apparent decrease of the field effect mobility with decreasing L and to a failure of the gradual channel approximation (GCA) in reproducing the output characteristics. Experimental data have been reproduced by two-dimensional numerical simulations that included a Schottky barrier (Φb=0.46eV) at both source and drain contacts and the effects of field-induced barrier lowering. The barrier lowering was found to be controlled by the Schottky effect for an electric field E<105V/cm, while for higher electric fields we found a stronger barrier lowering presumably due to other field-enhanced mechanisms. The analysis of numerical simulation results showed that three different operating regimes of the device can be identified: (1) low |Vds|, where the channel and the Schottky diodes at both source and drain behave as gate voltage dependent resistors and the partition between channel resistance and contact resistance depends upon the gate bias; (2) intermediate Vds, where the device characteristics are dominated by the reverse biased diode at the source contact, and (3) high |Vds|, where pinch-off of the channel occurs at the drain end and the transistor takes control of the current. We show that these three regimes are a general feature of the device characteristics when Schottky source and drain contacts are present, and therefore the same analysis could be extended to TFTs with different semiconductor active layers.

An SCR-Incorporated BJT Device for Robust ESD Protection With High Latchup Immunity in High-Voltage Technology

A silicon-controlled rectifier (SCR)-incorporated BJT with high holding voltage is developed for electrostatic discharge (ESD) protection in a 0.6 μm high-voltage 10 V process. This device consists simply of a floating P+ diffusion incorporated in a parasitic NPN BJT. A robust 6-7 kV ESD threshold and high-latchup-immune holding voltage of 15-18 V can be achieved by layout optimization of the NPN-N+ -collector to floating P+ -diffusion spacing and the floating P+ diffusion width. It can be equivalently regarded as parallel connection of an incorporated PNPN SCR part and an NPN BJT part. The incorporated SCR part is further composed of a parasitic SCR in series with a reverse-biased PN diode formed by the floating P+ region and N-well. The further analysis shows that the floating P+ diffusion is the key part of this SCR-incorporated BJT. The parasitic reverse-biased PN diode sustains most of the high holding voltage. The parasitic NPN BJT plays a major role in ESD current conduction, while the incorporated SCR in series with the reverse-biased PN diode is the secondary conduction path.

A silicon quasi-DOS based on reverse-biased pn diode

An interference-type silicon waveguide device, which uses the particularity of the overlap between the optical field and the depletion layer in the reverse-biased pn diode, has presented a “digital” response characteristic. Using this characteristic, a quasi-digital optical switch is proposed and discussed. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:635–638, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26618

Contact effects in high performance fully printed p-channel organic thin film transistors

Contact effects have been investigated in fully printed p-channel organic thin film transistors with field effect mobility up to 2 cm2/Vs. Electrical characteristics of the organic thin film transistors, with channel length &amp;lt;200 μm, are seriously influenced by contact effects with an anomalous increase of the contact resistance for increasing source-drain voltage. Assuming that contact effects are negligible in long channel transistors and using gradual channel approximation, we evaluated the current-voltage characteristics of the injection contact, showing that I-V characteristics can be modeled as a reverse biased Schottky diode, including barrier lowering induced by the Schottky effect.

Miniaturized Self-Oscillating Annular Ring Active Integrated Antennas

With a direct integration of a field effect transistor (FET) into a C-shaped ring radiator, a novel miniaturized self-oscillating annular ring active integrated antenna is proposed and investigated in this paper. The direct integration approach provides a solid basis for the miniaturization while the slow-wave loading effect from the unstable transistor further enhances the reduction ratio. It makes the proposed design show an extraordinarily compact size of 0.041λg2 , which is 40% the size of the second smallest one in literature using printed circuit board technology. The proposed active antenna, providing overall comparable performance to the previous designs, has an EIRP of 7.30 dBm, DC-to-RF efficiency of 25.9%, phase noise of -91.9 dBc/Hz@100 kHz offset, and an oscillator FOM of -168.76 dBc/Hz. By introducing a reverse-biased varactor diode, this miniaturized active antenna also demonstrates promising voltage controllability with a high VCO gain of 48.7 MHz/V. The antenna geometry and modeling, design concept, simulation scheme, and experimental results are discussed thoroughly in this paper.

A software tool for the design of high power PiN diodes based on the numerical study of the reverse characteristics

A physically based model of power PiN diodes was developed to simulate the reverse voltage behavior with purpose of design optimization for specific application. The model includes process simulation and 2D drift–diffusion simulation of the defined geometrical diode structure. The process simulation was adjusted to obtain the same doping profile measured on a known sample. Since bulk silicon and dopants used in high power device production are different from those used in VLSI, various analytical models of impurity diffusion phenomena were considered and parameters calibration was carried out within the range found in the literature to obtain the best fit with measurements. Impact ionization coefficients of the reverse biased diode model were tuned by comparison with measurements on a reference device and exploited to study the dependence of breakdown voltage vs. various technological parameters. A simulation campaign for many different diode structures was conducted. An ad hoc interpolation algorithm was developed and applied for using measurement and simulation results in quick design of diode structures for specific application.

Design and Analysis of Frequency-Tunable Amplifiers using Varactor Diode Topologies

The design of frequency-tunable amplifiers is investigated and the trade-off between linearity, efficiency and tunability is revealed. Several tunable amplifiers using various varactor diode topologies as tunable devices are designed by using load-pull techniques and their performances are compared. The amplifier using anti-series distortion-free varactor stack topology achieves 38% power added efficiency and it may be tuned from 1.74 to 2.36 GHz (about 35% tunable range). The amplifier using anti-series/anti-parallel topology is tunable from 1.74 to 2.14 GHz (about 23% tunable range) and provides 42% power added efficiency. It is demonstrated that tunable amplifiers using distortion-free varactor stack topologies provide better power added efficiency than the tunable amplifiers using reverse biased varactor diodes and their linearity is similar to that of a conventional amplifier. These amplifiers may facilitate the realization of frequency agile radio frequency transceiver front-ends and may replace several parallel connected amplifiers used in conventional multimode radios.

Broadband linearized silicon modulator

A scheme to achieve a wideband linearized silicon Mach-Zehnder (MZ) modulator is proposed. The modulator consists of a single MZ interferometer with identical reverse-biased silicon diode phase shifters in both arms, driven in a push-pull configuration. It is shown that the 3rd order nonlinearity of the modulator can be eliminated by canceling the nonlinearities from the silicon phase shifters and the MZ transfer function against each other. The 2nd order nonlinearity is simultaneously eliminated by differential detection or operation away from the quadrature point. As a result, the linearity of the proposed silicon modulator greatly exceeds the linearity of a conventional MZ modulator with ideal, linear (e.g. LiNbO3) phase shifters. The simplicity and large optical and RF bandwidth of the proposed modulator make it attractive for analog photonic applications.