Ideal Diode Research Articles

Fabrication of a Schottky Device Using CuSe Nanoparticles: Colloidal versus Microwave Digestive Synthesis.

Herein we report on a nearly ideal Schottky diode device fabricated from Cu(2-x)Se nanoparticles synthesized using the microwave digestive method. The thermionic theory using data extracted from the experimental I-V curve resulted in the ideality factor of 4.35 and the barrier height of 0.895 eV whilst the Cheung's method resulted in the ideality factor, barrier height and series resistance of 1.04, 0.00259 eV and 0.870 Ω respectively. The Cheung's method is thought to be the most accurate as it takes into account the series resistance. The obtained values therefore are indicative of good diode behaviour of the device and this is a highly sought after goal in all electronic materials development.

Current-transport mechanism in Au/V-doped PVC+TCNQ/p-Si structures

The forward and reverse bias current–voltage (I–V) characteristics of Au/V-doped polyvinyl chloride+Tetracyanoquino dimethane/porous silicon (PVC+TCNQ/p-Si) structures have been investigated in the temperature range of 160–340 K. The zero bias or apparent barrier height (BH) (Φ ap = Φ Bo ) and ideality factor (n ap = n) were found strongly temperature dependent and the value of n ap decreases, while the Φ ap increases with the increasing temperature. Also, the Φ ap versus T plot shows almost a straight line which has positive temperature coefficient and it is not in agreement with the negative temperature coefficient of ideal diode or forbidden bandgap of Si (α Si = -4.73×10-4 eV/K ). The high value of n cannot be explained only with respect to interfacial insulator layer and interface traps. In order to explain such behavior of Φ ap and n ap with temperature, Φ ap Versus q/2kT plot was drawn and the mean value of (Φ Bo ) and standard deviation (σs) values found from the slope and intercept of this plot as 1.176 eV and 0.152 V, respectively. Thus, the modified ( ln (Io/T2)-(qσs)2/2(kT)2 versus (q/kT) plot gives the Φ Bo and effective Richardson constant A* as 1.115 eV and 31.94 A ⋅(cm⋅K)-2, respectively. This value of A*( = 31.94 A⋅( cm ⋅K)-2) is very close to the theoretical value of 32 A ⋅(cm⋅K)-2 for p-Si. Therefore, the forward bias I–V–T characteristics confirmed that the current-transport mechanism (CTM) in Au/V-doped PVC+TCNQ/p-Si structures can be successfully explained in terms of the thermionic emission (TE) mechanism with a Gaussian distribution (GD) of BHs at around mean BH.

(Invited) Optoelectronic Properties and Electromechanical Resonance Behavior in Individual Suspended Carbon Nanotube Pn-Junctions and Devices

In carbon nanotubes pn-junctions, we observe Zener tunneling behavior and photocurrent generation in quasi-metallic nanotubes1, which have smaller band gaps than most known bulk semiconductors. These carbon nanotube-based devices deviate from conventional bulk semiconductor device behavior due to their low dimensional nature. We observe rectifying behavior based on Zener tunneling of ballistic carriers instead of ideal diode behavior, as limited by the diffusive transport of carriers. We observe substantial photocurrents at room temperature, suggesting that these quasi-metallic pn-devices may have a broader impact in optoelectronic devices. We also explore the role of weak clamping forces, typically assumed to be infinite, in the electromechanical resonance behavior of these suspended carbon nanotubes.2 Due to these forces, we observe a hysteretic clamping and unclamping of the nanotube device that results in a discrete drop in the mechanical resonance frequency on the order of 5−20 MHz, when the temperature is cycled between 340 and 375 K. This instability in the resonant frequency results from the nanotube unpinning from the electrode/trench sidewall where it is bound weakly by van der Waals forces. Interestingly, this unpinning does not affect the Q-factor of the resonance, since the clamping is still governed by van der Waals forces above and below the unpinning. For a 1 μm device, the drop observed in resonance frequency corresponds to a change in nanotube length of approximately 50−65 nm. On the basis of these findings, we introduce a new model, which includes a finite tension around zero gate voltage due to van der Waals forces and shows better agreement with the experimental data than the perfect clamping model. From the gate dependence of the mechanical resonance frequency, we extract the van der Waals clamping force to be 1.8 pN. The mechanical resonance frequency exhibits a striking temperature dependence below 200 K attributed to a temperature-dependent slack arising from the competition between the van der Waals force and the thermal fluctuations in the suspended nanotube. 1. Amer, M.R., S.-W. Chang, R. Dhall, J. Qiu and S. Cronin, “Zener Tunneling and Photocurrent Generation in Quasi-Metallic Carbon Nanotube pn-Devices” Nano Letters, 13, 5129 (2013). 2. Mehmet Aykol, Bingya Hou, Rohan Dhall, Shun-Wen Chang, William Branham, Jing Qiu, and Stephen Cronin, "Clamping Instability and van der Waals Forces in Carbon Nanotube Mechanical Resonators" Nano Letters, 14, 2426 (2014). 3. Shun-Wen Chang, Kevin Bergemann, Rohan Dhall, Jeramy Zimmerman, Stephen Forrest, Stephen Cronin, "Non-ideal Diode Behavior and Band Gap Renormalization in Carbon Nanotube P-N Junctions" IEEE Transactions on Nanotechnology, 13, 41 (2014).

On the Lipschitz Behavior of Solution Maps of a Class of Differential Inclusions

We consider a general differential inclusion which is parameterized by a parameter. We perform time discretization and present conditions under which the discretized solution map is locally Lipschitz. Further, if the Lipschitzian modulus is bounded in some sense, we show that it is possible to obtain the local Lipschitzian property even for the original (not discretized) solution map. We conclude the paper with an example concerning stability analysis of nonregular electrical circuits with ideal diodes.

Calculation of the electronic parameters of an Al/DNA/p-Si Schottky barrier diode influenced by alpha radiation.

Many types of materials such as inorganic semiconductors have been employed as detectors for nuclear radiation, the importance of which has increased significantly due to recent nuclear catastrophes. Despite the many advantages of this type of materials, the ability to measure direct cellular or biological responses to radiation might improve detector sensitivity. In this context, semiconducting organic materials such as deoxyribonucleic acid or DNA have been studied in recent years. This was established by studying the varying electronic properties of DNA-metal or semiconductor junctions when exposed to radiation. In this work, we investigated the electronics of aluminium (Al)/DNA/silicon (Si) rectifying junctions using their current-voltage (I-V) characteristics when exposed to alpha radiation. Diode parameters such as ideality factor, barrier height and series resistance were determined for different irradiation times. The observed results show significant changes with exposure time or total dosage received. An increased deviation from ideal diode conditions (7.2 to 18.0) was observed when they were bombarded with alpha particles for up to 40 min. Using the conventional technique, barrier height values were observed to generally increase after 2, 6, 10, 20 and 30 min of radiation. The same trend was seen in the values of the series resistance (0.5889–1.423 Ω for 2–8 min). These changes in the electronic properties of the DNA/Si junctions could therefore be utilized in the construction of sensitive alpha particle detectors.

Analysis of Photovoltaic (PV) Module during Partial Shading based on Simplified Two-Diode Model

Abstract Generally, the characteristics of photovoltaic (PV) array are largely affected by solar temperature, solar irradiance, shading patterns, array configuration and location of shading modules. Partial shading is due to moving clouds and shadows of nearby obstacles and can cause a significant degradation in the output of PV system. Hence, the characteristics of PV array get more multifaceted with multiple peaks. The ultimate aim of the paper is to analyze the performance of PV module during such adverse condition based on simplified two-diode model. To reduce the computational time, the simplified two-diode model has a photocurrent source in parallel with two ideal diodes. Only four parameters are required to be calculated from datasheet in order to simulate the model. Moreover, the performance of PV array is evaluated at different shaded patterns and it is found that the model has less computational time and gives accurate results.

Equivalent Circuit Modelling for Pulsed Bipolar Plasma Electrolytic Oxidation Process

 Abstract—The paper discusses modelling and simulation problems for the technological process of plasma electrolytic oxidation (PEO) of light alloys, presented as an electric load, for the purposes of the process understanding and control. It is shown that the transient processes of voltage and current during PEO can be simulated by a second order nonlinear circuit consisting of resistors, capacitors, an inductor and ideal diodes. The properties of the circuit components follow the coating growth; this dependency can be used for the process control.

Analytical Studies of Metal Insulator Semiconductor Schottky Barrier Diodes

The current –voltage data of the metal –insulator semiconductor Schottky diode are simulated using thermionic emission diffusion equation taking into account the inter facial layer parameters.The computed current – voltage data are fitted into ideal thermionic emission diffusion equation to see the apparent effect of interfacial parameters on current transport.In presence of interfacial layer the Schottky contact behave as an ideal diode of apparently high barrier height. The behavior of apparent height and ideality factor with the presence of inter facial layer is discussed.

PRACTICAL REALIZATION OF IDEAL DIODE FULL-WAVE RECTIFIERS

This paper discuses practical realization of full-wave rectifiers made of electronic diodes for high current bipolar electronic loads. The presented solution minimizes the voltage drop and nonlinearity of loads in the region of low voltages. Compared to standard or Schottky diodes, electronic (also referred to as ideal) diodes exhibit very low voltage drop and power dissipation. In the full-wave rectifier, MOSFETs with very low RDSon (low units of milliohms) are used. Ideal rectifiers have been traditionally used as structural elements in switched power supplies; they are often applied in low dissipation power switches and started to be utilized as full-wave rectifiers.

F4-TCNQ concentration dependence of the current—voltage characteristics in the Au/P3HT:PCBM:F4-TCNQ/n-Si (MPS) Schottky barrier diode

In this study, we investigate some main electrical parameters of the gold/poly(3-hexylthiophene):[6,6]-phenyl C61 butyric acid methyl ester:2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane/n-type silicon (Au/P3HT:PCBM:F4-TCNQ/n-Si) metal—polymer—semiconductor (MPS) Schottky barrier diode (SBD) in terms of the effects of F4-TCNQ concentration (0%, 1%, and 2%). F4-TCNQ-doped P3HT:PCBM is fabricated to figure out the p-type doping effect on the device performance. The main electrical parameters, such as ideality factor (n), barrier height (ΦB0), series resistance (Rs), shunt resistance (Rsh), and density of interface states (Nss) are determined from the forward and reverse bias current—voltage (I–V) characteristics in the dark and at room temperature. The values of n, Rs, ΦB0, and Nss are significantly reduced by using the 1% F4-TCNQ doping in P3HT:PCBM:F4-TCNQ organic blend layer, additionally, the carrier mobility and current are increased by the soft (1%) doping. The most ideal values of electrical parameters are obtained for 1% F4-TCNQ used diode. On the other hand, the carrier mobility and current for the hard doping (2%) become far away from the ideal diode values due to the unbalanced generation of holes/electrons and doping-induced disproportion when compared with 1% F4-TCNQ doping. These results show that the electrical properties of MPS SBDs strongly depend on the F4-TCNQ doping and doping concentration of interfacial P3HT:PCBM:F4-TCNQ organic layer. Moreover, the soft F4-TCNQ doping concentration (1%) in P3HT:PCBM:F4-TCNQ organic layer significantly improves the electrical characteristics of the Au/P3HT:PCBM:F4-TCNQ/n-Si (MPS) SBDs which enables the fabricating of high-quality electronic and optoelectronic devices.

Effect of axial halogen substitution on the performance of subphthalocyanine based organic photovoltaic cells

To probe the influence of molecular dipole on the open circuit voltage (VOC) of molecular heterojunction organic solar cells, we study axially fluorinated boron subphthalocyanine/fullerene (SubPc-F/C60) junctions. These exhibit an open-circuit voltage VOC=1.00V, a value closer to the HOMO–LUMO offset at the donor–acceptor interface=1.69eV than the VOC=1.06V measured for junctions between the archetypal chlorinated SubPc and C60, with corresponding HOMO–LUMO offset=1.84eV. Aside from the axial halogen substitution, the two compounds exhibit similar molecular structure and optical absorption. The energy levels and structure of the heteromolecular polaron pair are calculated, and the ideal organic diode model for SubPc-Cl is modified accordingly, successfully reproducing the experimental SubPc-F device characteristics. The reproducible difference in VOC is attributed to the different electric dipole strength between SubPc-F and SubPc-Cl and its influence on polaron pair dynamics at the heterojunction.

The effect of pH and selenization on the properties of CuInSe2 thin films prepared by electrodeposition technique for device applications

We have synthesized CuInSe2 (CIS) thin films from an aqueous electrolyte by potentiostatic electrochemical technique at room temperature. The effects of pH and selenization on the properties of CIS layer have been thoroughly investigated. The studies were carried out on the samples prepared in as-prepared bath with pH 2.5 and later adjusted to 1.2. Cyclic voltammetry (CV) was studied at slow scan rate to optimize the deposition parameters. The prepared thin films were selenized in a tubular furnace at 400 °C for 20 min in selenium atmosphere. Structural, optical, compositional, morphological, and electrical properties were studied with the help of X-ray diffractometer, Uv-vis absorption spectroscopy, energy dispersive X-ray analysis (EDAX), scanning electron microscopy (SEM), and current–voltage (I–V) measurements. The prominent reflections (112), (204/220), and (312/116) of tetragonal CIS have been exhibited for all as-deposited and selenized samples. The energy band gap of the selenized CIS thin film was found to be ~1.03 eV. Granular, uniform, and densely packed surface morphology was observed for as-deposited and selenized samples electrodeposited at −0.6 and −0.8 V versus Ag/AgCl for the pH of bath 1.2 and 2.5, respectively. EDAX result reveals the stoichiometric CIS films can be electrodeposited at −0.6 and −0.8 V with pH of the bath 1.2 and 2.5, respectively. The ideality factor (η) deducted from I–V measurements was found to be reduced from 1.6 to 1.3 and 1.9 to 1.2 after selenization of samples grown at −0.6 and −0.8 V, respectively, revealing the formation of ideal diode due to elimination of surface leakage current. Photoelectrochemical (PEC) measurement confirms the growth of p-type CIS thin film.

PERFORMANCE COMPARISON OF p–n JUNCTION DIODES USING ZINC OXIDE AND COPPER PHTHALOCYANINE HYBRID NANOCOMPOSITES AND BILAYER HETEROSTRUCTURES

Nanocomposites of n-type Zinc Oxide ( ZnO ) and p-type copper phthalocyanine ( CuPc ) were synthesized using solution route and the electrical properties of heterojunctions of ZnO and CuPc in the nanocomposite film was studied. For comparison, electrical properties of bilayer heterojunction devices using ZnO nanostructure drop cast film and thermally evaporated CuPc were also studied. Rectification ratio (RR) of about 28 and 5.5 was obtained at 4 V for devices with nanocomposite film and bilayer heterojunctions indicating improved formation of p–n junction characteristics for nanocomposite films. Values of ideality factor, barrier height at the p–n junction interface and series resistance were estimated using different methods like semilog plots, Cheung and Norde's methods. Ideality factor estimated from semilog plots and Cheung's methods were found to be higher than unity indicating deviation from ideal diode behavior. Barrier height estimated from different methods was about 0.7 eV. Series resistance measured using Cheung and Norde's methods were found to be about 92 KΩ and 21 KΩ, respectively. Bilayer heterojunction devices exhibited much higher series resistance, ideality factor and barrier height as estimated using all the above-mentioned methods as compared to the devices with nanocomposite film. The above results indicate intimate mixing and improved interface between ZnO and CuPc in the in situ synthesized nanocomposite film thereby offering improved p–n junction characteristics.

Ideal graphene/silicon Schottky junction diodes.

The proper understanding of semiconductor devices begins at the metal-semiconductor interface. The metal/semiconductor interface itself can also be an important device, as Schottky junctions often forms when the doping in the semiconductors is low. Here, we extend the analysis of metal-silicon Schottky junctions by using graphene, an atomically thin semimetal. We show that a fundamentally new transport model is needed to describe the graphene-silicon Schottky junction. While the current-voltage behavior follows the celebrated ideal diode behavior, the details of the diode characteristics is best characterized by the Landauer transport formalism, suggesting that the injection rate from graphene ultimately determines the transport properties of this new Schottky junction.

A Novel Simplified Two-Diode Model of Photovoltaic (PV) Module

This paper proposes a novel simplified two-diode model of a photovoltaic (PV) module. The main aim of this study is to represent a PV module as an ideal two-diode model. In order to reduce computational time, the proposed model has a photocurrent source, i.e., two ideal diodes, neglecting the series and shunt resistances. Only four unknown parameters from the datasheet are required in order to analyze the proposed model. The simulation results that are obtained by MATLAB/Simulink are validated with experimental data of a commercial PV module, using different PV technologies such as multicrystalline and monocrystalline, supplied by the manufacturer. It is envisaged that this work can be useful for professionals who require a simple and accurate PV simulator for their design.

The pn Junctions of Epitaxial Germanium on Silicon by Solid Phase Doping

Boron and phosphorous layers were deposited by ultrahigh-vacuum chemical vapor deposition at 450 °C using B2H6 and PH3, respectively, to form the abrupt doping profiles in epitaxial Ge on Si substrate. The diffusion process without ion implantation damage is demonstrated by the nearly ideal diode characteristics for the first time. The Ge diodes doped by the boron layer and the phosphorous layer have the ON/OFF ratio of \(\sim 1\times 10^{5}\) and \(\sim 1.5\times 10^{5}\) with the extremely low reverse current densities of \(\sim 1\times 10^{-4}\) A/cm \(^{2}\) and \(\sim 4\,\times \,10^{-5}\) A/cm \(^{2}\) , respectively. The good crystalline quality at junction free from implantation damage by in situ solid phase doping reflects these figures of merit.

On the electrical and interface properties of nanostructured CdTe Schottky diodes electrodeposited from an ionic liquid medium

A simple and cost effective method to fabricate nearly ideal Schottky diode out of p-CdTe semiconductor is discussed. The efficient re-use of ionic liquid for the deposition of nano-microstructures of CdTe is also disclosed. The I–V characteristic of the diode configured as Cu:FTO:p-CdTe:Cu showed the rectifying nature with a small forward voltage (0.8 V) and a rectification ratio of 6 × 103 at 4.8 V. Theoretical model suggests the diffusion controlled carrier transport process with an ideality factor of 1.1 up to a small forward voltage range whereas the thermionic transport with generation recombination dominates at higher voltages. The interface properties of p-CdTe and FTO were studied by impedance spectroscopy under varied bias conditions to electrically represent the diode.

Carrier Escape and the Ideality Factor in Quantum Dot p-n Junctions

The ideal diode approximation is used to evaluate the properties of many semiconductor diode-based devices. However, when it is applied to lasers and photovoltaics, which incorporate quantum dots (QDs), the ideality factors measured are difficult to interpret. Here, we show that a proper consideration of carrier escape from the QD confined states overcomes this problem. In addition, this approach suggests a novel method of empirically estimating the absolute value of the escape current at the threshold current of a laser diode. We argue that this technique will be of great importance in the experimental analysis of nonradiative losses in lasers and should also prove useful to the development of next-generation QD photovoltaics where thermal carrier escape must be minimized.

Passivation of the GaP(111) surface by treatment in selenium vapors

Results of examination of structural phase transitions on the GaP(111) surface after heat treatment in selenium vapors in a vacuum chamber with a quasi-closed volume are described. The electrophysical characteristics of Schottky-barrier diodes on GaP(111) are studied before and after treatment in selenium vapors by measuring the current-voltage characteristics and by deep-level transient spectroscopy. It is found that, after treatment in selenium vapors, the Schottky-barrier height becomes dependent on the work function of the metal in accordance with the Schottky-Mott rule for an ideal diode. It is shown that a decrease in the density of surface electronic states in GaP(111) results from the formation of a Ga2Se3(111)(√3 × √3)-R30° surface phase with ordered stoichiometric gallium vacancies.

Nonideal Diode Behavior and Bandgap Renormalization in Carbon Nanotube p-n Junctions

The p-n junction diodes are formed by electrostatic doping using two gate electrodes positioned beneath individual, suspended single-walled carbon nanotubes (CNTs). These devices exhibit nearly ideal diode behavior within a small bias voltage range near 0 V. At higher bias (>\vert 0.2 V\vert), nonideal diode behavior is observed arising from Schottky contacts formed between the nanotube and its metal contact electrodes and the presence of electron tunneling between the N- and P-doped regions. We introduce a back-to-back diode model to explain the observed current versus voltage (I-V) characteristics. The reverse saturation current, parallel resistance, and open-circuit voltage dependence on gate voltage provide quantitative evidence for the theoretically predicted doping-induced bandgap shrinkage in CNTs. The minority carrier lifetimes are also estimated from this model.