Ideal Diode Research Articles

MEMS climate sensor for crops in greenhouses

We have developed and fabricated a multi-sensor chip for greenhouse applications and demonstrated the functionality under controlled conditions. The sensor consists of a humidity sensor, temperature sensor and three photodiodes sensitive to blue, red and white light, respectively. The humidity sensor responds linearly with humidity with a full scale change of 5.6 pF. The best performing design measures a relative change of 48%. The temperature sensor responds linearly with temperature with a temperature coefficient of resistance of 3.95 × 10−3 K−1 and a sensitivity of 26.5 Ω °C−1. The three photodiodes have been characterized and show an almost ideal diode behavior with an ideality factor of 1.27 and a series resistance of 14.9 Ω. The diodes are sensitive to blue, red and white light with the measured quantum efficiencies of 69%, 81% and 68%, respectively. The temperature and humidity sensors have further been tested on plants in a greenhouse, demonstrating that individual plant behavior can be monitored.

Temperature and electric field dependent mobility in poly(3-hexylthiophene) diodes

Current-voltage (I-V) curves of poly(3-hexylthiophene) (P3HT) diodes have been collected to investigate the polymer hole-dominated charge transport. At room temperature and at low electric fields the I-V characteristic is purely Ohmic whereas at medium-high electric fields, experimental data shows that the hole transport is trap dominated in the space charge limited current (SCLC) regime. In this regime, it is possible to extract the I-V characteristic of the P3HT/Al junction showing the ideal Schottky diode behavior over five orders of magnitude. At high-applied electric fields, holes’ transport is found to be in the trap free SCLC regime. We have measured and modeled in this regime the holes’ mobility to evaluate its dependence from the electric field applied and the temperature of the device.

Interface characteristics of n-n and p-n Ge/SiC heterojunction diodes formed by molecular beam epitaxy deposition

In this article, we report on the physical and electrical nature of Ge/SiC heterojunction layers that have been formed by molecular beam epitaxy (MBE) deposition. Using x-ray diffraction, atomic force microscopy, and helium ion microscopy, we perform a thorough analysis of how MBE growth conditions affect the Ge layers. We observe the layers developing from independent islands at thicknesses of 100 nm to flat surfaces at 300 nm. The crystallinity and surface quality of the layer is shown to be affected by the deposition parameters and, using a high temperature deposition and a light dopant species, the layers produced have large polycrystals and hence a low resistance. The p-type and n-type layers, 300 nm thick are formed into Ge/SiC heterojunction mesa diodes and these are characterized electrically. The polycrystalline diodes display near ideal diode characteristics (n<1.05), low on resistance and good reverse characteristics. Current-voltage (I-V) measurements at varying temperature prove that all the layers have two-dimensional fluctuations in the Schottky barrier height (SBH) due to inhomogeneities at the heterojunction interface. Capacitance-voltage analysis and the SBH size extracted from I-V analysis suggest strongly that interface states are present at the surface causing Fermi-level pinning throughout the bands. A simple model is used to quantify the concentration of interface states at the surface.

The interpretation of the DC characteristics of LED and laser diodes to address their failure analysis

The interpretation of the forward DC characteristics of LEDS and laser diodes is shown as a valuable tool to infer the internal structure of real devices and to address their analysis after failures. To this purpose, the self-consistent I( V) DC transfer function for the ideal laser diode is introduced.

Investigation of hydrogen sensing properties and aging effects of Schottky like Pd/porous Si

We prepared porous silicon samples coated by continuous palladium layer in electroless process. Scanning electron microscopy (SEM) showed cauliflower-shape Pd clusters on the surface. I– V curves of Schottky like Pd/porous Si samples were measured in air and in hydrogen. These measurements showed a metal–interface–semiconductor configuration rather than an ideal Schottky diode. Variations of the electrical current in the presence of diluted hydrogen at room temperature revealed that the samples can sense hydrogen in a wide range of concentration (100–40,000 ppm) without any saturation behavior. Hydrogen sensing properties of these samples were investigated at room temperature for a duration of nine months. Sample sensitivity (response time) decreased (increased) to a saturated value after 45 days. We discussed sensing and Schottky contact properties of the fresh and aged Pd/porous Si samples by variation of structure and chemical composition using SEM, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) data.

Performance characteristics of an irreversible engine consisting of nonlinear diodes system

The performance of an irreversible engine consisting of a nonlinear diodes system is presented. The system consists of two diodes switched in the opposite directions and located in two reservoirs at different temperatures, and the two diodes are connected in parallel with a capacitor. Based on the theory of thermal fluctuations, the expressions of the heat fluxes absorbed from the hot and cold reservoirs are derived. When the heat leak between the two reservoirs is taken into account, the power output and the efficiency of the engine can be obtained. The performance characteristic curves are plotted and the characteristic relations between the optimum performance parameters and the ratio of the temperatures are obtained by numerical simulation. The influence of the main parameters, including the nonlinearity of the diodes, the loss of heat leak and the ratio of temperatures of two reservoirs, on the performance characteristics of the engine is analyzed in detail. Finally, the performance characteristics of the ideal diodes engine are discussed.

Electrical Properties of Pt/Nb-Doped SrTiO<sub>3</sub> Schottky Junctions

In this study, we successfully fabricated the Schottky junctions consisting of Pt electrode and high concentration Nb-doped (0.5 wt%) SrTiO3 (001) single crystal by sputtering process. The carrier concentrations of Nb-0.5wt%-doped SrTiO3 were determined as 1020 /cm3 order by Hall effect measurement. The electrical properties of junctions were investigated by measuring their current-voltage (I-V), capacitance-voltage (C-V) characteristics at temperature range from 80K to 400K. The hysteresis feature was observed that indicating the alteration of barrier height in junctions especially at lower temperature. The donor concentration and built-in potentials calculated from C-2-V data showed large discrepancy from Hall effect measurement indicating that the junctions deviate from the ideal Schottky diode model.

Time-Stepping Numerical Simulation of Switched Circuits Within the Nonsmooth Dynamical Systems Approach

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> The numerical integration of switching circuits is known to be a tough issue when the number of switches is large, or when sliding modes exist. Then, classical analog simulators may behave poorly, or even fail. In this paper, it is shown on two examples that the nonsmooth dynamical systems (NSDS) approach, which is made of: 1) a specific modeling of the piecewise-linear electronic devices (ideal diodes, Zener diodes, transistors); 2) the Moreau's time-stepping scheme; and 3) specific iterative one-step solvers, supersedes simulators of the simulation program with integrated circuit emphasis (SPICE) family and hybrid simulators. An academic example constructed in [Maffezzoni, <etal/>, IEEE Trans. CADICS, vol 25, no. 11, Nov. 2006], so that the Newton–Raphson scheme does not converge, and the buck converter are used to make extensive comparisons between the NSDS method and other methods of the SPICE family and a hybrid-like method. The NSDS method, implemented in the <emphasis emphasistype="smcaps">siconos</emphasis> platform developed at INRIA, proves to be on these two examples much faster and more robust with respect to the model parameter variations. </para>

BN/ZnO heterojunction diodes with apparently giant ideality factors

Until now, a common feature of many wide band gap heterojunction diodes is an unexplained large ideality factor n&amp;gt;2. In this context we investigate the diode characteristics of heterojunction diodes consisting of a crystalline semiconductor material such as ZnO covered with a thin semiconducting film of amorphous or disordered material. As thin disordered film we use sp2-bonded turbostratic boron nitride. These heterojunctions exhibit a pronounced rectifying behavior, low saturation current, and low parasitic currents. Moreover, we observe an apparently giant ideality factor reaching values of n&amp;gt;100. As a consequence, the turn-on voltage is around 5–10 V and the I-V curves can be measured for bias voltages between ±80 V without reaching saturation or electrical breakdown. We present a quantitative model for the unusual diode characteristics of these metal-amorphous semiconductor-semiconductor diodes. We demonstrate that the I-V characteristics of the heterojunctions are well described by a serial arrangement of an ideal Schottky diode, a Frenkel–Poole type resistance, and an Ohmic contact resistance, emulating a p-n- or Schottky diode characteristic with giant ideality factor. We propose that heterojunctions exhibiting apparently large ideality factors n⪢2 may possess an interfacial disordered or amorphous layer with Frenkel–Poole conduction properties.

In situ scanning electron microscope electrical characterization of GaN nanowire nanodiodes using tungsten and tungsten/gallium nanoprobes

A lithography-free technique for measuring the electrical properties of n-type GaN nanowires has been investigated using nanoprobes mounted in a scanning electron microscope (SEM). Schottky contacts were made to the nanowires using tungsten nanoprobes, while gallium droplets placed in situ at the end of tungsten nanoprobes were found to be capable of providing Ohmic contacts to GaN nanowires. Schottky nanodiodes were fabricated based on single n-type nanowires, and measured current–voltage ( I – V ) results suggest that the Schottky nanodiodes deviate from ideal diodes mainly due to their nanoscopic contact area. Additionally, the effect of the SEM electron beam on the I – V characteristics was investigated and was found to impact the transport properties of the Schottky nanodiodes, possibly due to an increase in carrier density in the nanodiodes.

Optical properties of chiral photonic crystals with linear profiles of modulation parameters

The oblique propagation of light through a layer of chiral photonic crystal (PC) with linear profiles of modulation parameters is considered. The problem is solved by the method of Ambartsumyan layer addition. The wavelength dependences of the amplitude characteristics have been studied at different angles of incidence in two cases, i.e., in a chiral PC with a linear profile of modulation period and a chiral PC with a linear profile of modulation depth. It is shown that the photonic band gap is broadened in both cases and that omnidirectional reflection occurs under certain conditions. The nonreciprocity features are investigated for these two cases and it is shown that a chiral PC with a linear profile of modulation period can operate as an ideal optical diode in a certain frequency range. The features of the effect of change in the modulation parameters on the photon density of states, group velocity, and group velocity dispersion are analyzed. It is shown that, when the modulation parameters change in space, the photon density of states at the photonic band gap edges significantly decreases. It is proposed to use PCs with a spatially changing modulation period can be used to compress (expand) light pulses.

A simple numerical model for the charge transport and recombination properties of dye-sensitized solar cells: A comparison of transport-limited and transfer-limited recombination

A simple model is presented for the charge transport and recombination characteristics of dye-sensitized solar cells (DSCs), based on solving the continuity equation for electrons using numerical methods. We analyze two models, in which the recombination kinetics are determined by either the electron transport kinetics in the nanostructured metal oxide film or the electron transfer rate across the metal oxide–electrolyte solution interface. It is found that transport-limited recombination results in ideal diode behaviour, in which case the open-circuit voltage is proportional to the logarithm of the light intensity with a slope of 26 mV, while the transfer-limited model allows for a different slope that depends on the trap distribution parameter, α, and the electron transfer coefficient, b.

Calculation of current–voltage characteristics of a Cu (II) complex/n-Si/AuSb Schottky diode

In this study, Cu (II) complex/n-Si structure has been fabricated by forming a thin organic Cu (II) complex film on n-Si wafer. It has been seen that the structure has clearly shown the rectifying behaviour and can be evaluated as a Schottky diode. The contact parameters of the diode such as the barrier height and the ideality factor have been calculated using several methods proposed by different authors from current–voltage ( I– V) characteristics of the device. The calculated barrier height and ideality factor values from different methods have shown the consistency of the approaches. The obtained ideality factor which is greater than unity refers the deviation from ideal diode characteristics. This deviation can be attributed to the native interfacial layer in the organic/inorganic interface and the high series resistance of the diode. In addition, the energy distribution of the interface state density ( N ss ) in the semiconductor band gap at Cu (II) complex/n-Si interface obtained from I– V characteristics range from 2.15 × 10 13 cm −2 eV −1 at ( E c − 0.66) eV to 5.56 × 10 12 cm −2 eV −1 at ( E c − 0.84) eV.

Weak rectifying behaviour of p-SnS/n-ITO heterojunctions

This work explores the electrical properties of p-SnS/n-ITO heterojunction at different temperatures. The p-type SnS film was deposited on n-type ITO substrate using the thermal evaporation technique and its junction properties were studied using two probe method. The as-grown p–n junction exhibited weak rectifying behaviour with a low saturation current of the order of ∼10−6A. While increasing temperature, the saturation current of the junction is increased and however, its series resistance decreased. At all temperatures the junction exhibited three types of transport mechanisms depending on applied bias-voltage. At lower voltages the junction showed nearly ideal diode characteristics. The junction behaviour with respect to bias-voltage and temperature is discussed with the help of existing theories and energy band diagram.

Assessing the Impact of SiC MOSFETs on Converter Interfaces for Distributed Energy Resources

Distributed energy resources (DERs) are becoming integral components of electric power distribution systems. In most cases, an isolated DC-DC converter forms part of the interface required to connect the DER output to the distribution system. Operation of the converter at high switching frequencies results in size reduction of passive components at the expense of increased switching losses. However, silicon carbide (SiC) power devices have the potential of operating at high switching frequencies without significant loss penalty because of their fast switching times and ability to work at high temperatures when compared to similar Si devices. SiC diodes have already displayed the ability to offer more ideal diode behavior than Si diodes. Engineering samples of SiC MOSFETs are depicting lower switching losses and conduction losses over Si MOSFETs. This display is making SiC devices attractive for DC-DC converters used to connect DERs to the distribution system. This paper particularly deals with the design of a 300 W 100 kHz DC-DC full-bridge converter using zero-voltage zero-current switching for comparison of SiC MOSFETs and diodes against Si MOSFETs and diodes.

A High Performance CCM PFC Circuit Using a SiC Schottky Diode and a Si SuperFET&lt;sup&gt;TM&lt;/sup&gt; Switch

SuperFETTM MOSFETs and silicon carbide (SiC) Schottky diodes are applied to continuous conduction mode active power factor correction pre-regulators. SuperFETTM MOSFETs can reduce power losses dramatically with their extremely low RDS(ON) and fast switching. The SiC Schottky diode has virtually zero reverse recovery current and high thermal conductivity, and is close to an ideal diode for a CCM PFC circuit. Due to these outstanding switching characteristics, frequency can be increased. In this paper, the SiC Schottky diode’s and SuperFETTM MOSFET’s performance have been verified in a CCM PFC boost converter. These products can reduce the total power losses and enhance the system efficiency.

The influence of series resistance and interface states on intersecting behavior of I–V characteristics of Al/TiO2/p-Si (MIS) structures at low temperatures

In this study, we have investigated the intersection behavior of the forward bias current–voltage (I–V) characteristics of the Al/TiO2/p-Si (MIS) structures in the temperature range of 100–300 K. The intersection behavior of the I–V curves appears as an abnormality when compared to the conventional behavior of ideal Schottky diodes and MIS structures. This behavior is attributed to the lack of free charge at a low temperature and in the temperature region, where there is no carrier freezing out, which is non-negligible at low temperatures, in particular. The values calculated from the temperature-dependent forward bias I–V data exhibit unusual behavior, where the zero-bias barrier height (ϕb0) and the series resistance (Rs) increase with increasing temperature. Such temperature dependence of ϕb0 and Rs is in obvious disagreement with the reported negative temperature coefficient. An apparent increase in the ideality factor (n) and a decrease in the ϕb0 at low temperatures can be attributed to the inhomogeneities of the barrier height, the thickness of the insulator layer and non-uniformity of the interfacial charges. The temperature dependence of the experimental I–V data of the Al/TiO2/p-Si (MIS) structures has revealed the existence of a double Gaussian distribution with mean barrier height values () of 1.108 eV and 0.649 eV, and standard deviations (σs) of 0.137 V and 0.077 V, respectively. Furthermore, the temperature dependence of the energy distribution of interface state density (Nss) profiles has been determined from forward bias I–V measurements by taking into account the bias dependence of the effective barrier height (ϕe) and n. The fact that the values of Nss increase with increasing temperature has been attributed to the molecular restructuring and reordering at the metal/semiconductor interface under the effect of temperature.

Metal-semiconductor-metal photodetectors based on single-walled carbon nanotube film–GaAs Schottky contacts

We demonstrate the Schottky behavior of single-walled carbon nanotube (CNT) film contacts on GaAs by fabricating and characterizing metal-semiconductor-metal (MSM) photodetectors with CNT film electrodes. We extract the Schottky barrier height of CNT film contacts on GaAs by measuring the dark I-V characteristics as a function of temperature. The results show that at temperatures above ∼260 K, thermionic emission of electrons with a barrier height of ∼0.54 eV is the dominant transport mechanism in CNT film–GaAs junctions, whereas at lower temperatures, tunneling begins to dominate suggested by the weak dependence of current on temperature. Assuming an ideal MS diode, this barrier height corresponds to a CNT film workfunction of ∼4.6 eV, which is in excellent agreement with the previously reported values. Furthermore, we characterize the effect of device geometry on the dark current and find that dark currents of the MSM devices scale rationally with device geometry, such as the device active area, finger width, and finger spacing. Finally, we compare the dark and photocurrent of the CNT film-based MSM photodetectors with standard metal-based MSMs. We find that MSM devices with CNT film electrodes exhibit a higher photocurrent-to-dark current ratio while maintaining a comparable responsivity relative to metal control devices. These results not only provide valuable information about the fundamental properties of the CNT film–GaAs interface but also open up the possibility of integrating CNT films as transparent and conductive Schottky electrodes in conventional semiconductor electronic and optoelectronic devices.

Transport properties in C60 field-effect transistor with a single Schottky barrier

C 60 field-effect transistor (FET) has been fabricated with a single Schottky barrier formed by an insertion of 1-dodecanethiol at the interface between the active layer and the gate dielectric. The suppression of drain current is observed at low drain-source voltage, showing a formation of the carrier injection barrier. Furthermore, a clear difference between forward and reverse drain currents is observed in the FET in a high temperature region, showing that this FET device is close to an ideal single Schottky diode. The quantitative analysis for carrier injection barrier has been achieved with thermionic emission model for a single Schottky barrier.

A nearly ideal phosphor-converted white light-emitting diode

A phosphor-converted light-emitting diode was obtained with nearly ideal blue-to-white conversion loss of only 1%. This is achieved using internal reflection to steer phosphor emission away from lossy surfaces, a reflector material with high reflectivity, and a remotely located organic phosphor having (1) unity quantum efficiency (ηq), (2) homogeneous refractive index to minimize scattering, and (3) refractive index-matched to the encapsulation to eliminate total internal reflection. An inorganic composite phosphor is also reported with a nearly homogeneous refractive index to minimize diffuse scattering of emitted light, thereby maximizing the effective phosphor ηq and light extraction.