Electronic Properties of ZnO Varistors: A New Model

1981 ◽  
Vol 5 ◽  
Author(s):  
G. E. Pike
Keyword(s):  
Grain Boundaries ◽  
Impact Ionization ◽  
Thermionic Emission ◽  
Low Frequency ◽  
Charge Trapping ◽  
Emission Model ◽  
Zero Bias ◽  
Current Voltage ◽  
Zno Varistors ◽  
Dc Current

ABSTRACTMuch of the research on ZnO varistors has concentrated on the explanation of their dc current-voltage characteristics. However, varistors also have unusual ac properties which can be technologically important, and must be described by any comprehensive model. In an ideal varistor with identical grain boundaries throughout, there should be no dispersive capacitance at zero bias. In real varistors this capacitance varies considerably with frequency. This dispersion has two causes, charge trapping in the depletion regions and differing grain boundary barriers. Calculations for each process are given. For voltages well below the varistor breakdown value, the low frequency capacitance increases with applied voltage. At even higher voltages the capacitance turns over and becomes negative. All of these effects can be described with a double depletion layer/thermionic emission model. The anomalous capacitance behavior with bias is due to the modulation of the potential barriers by charge trapping at the grain boundaries. In the varistor breakdown regime minority carriers created by impact ionization are important.

Investigation of carrier transport mechanisms in the Cu–Zn–Se based hetero-structure grown by sputtering technique

2018 ◽  
Vol 96 (7) ◽  
pp. 816-825 ◽  
Author(s):  
H.H. Güllü ◽  
M. Terlemezoğlu ◽  
Ö. Bayraklı ◽  
D.E. Yıldız ◽  
M. Parlak
Keyword(s):  
Barrier Height ◽  
Carrier Transport ◽  
Thermionic Emission ◽  
Electrical Characterization ◽  
Band Gap Energy ◽  
Zero Bias ◽  
Hetero Structure ◽  
Current Voltage ◽  
P Type

In this paper, we present results of the electrical characterization of n-Si/p-Cu–Zn–Se hetero-structure. Sputtered film was found in Se-rich behavior with tetragonal polycrystalline nature along with (112) preferred orientation. The band gap energy for direct optical transitions was obtained as 2.65 eV. The results of the conductivity measurements indicated p-type behavior and carrier transport mechanism was modelled according to thermionic emission theory. Detailed electrical characterization of this structure was carried out with the help of temperature-dependent current–voltage measurements in the temperature range of 220–360 K, room temperature, and frequency-dependent capacitance–voltage and conductance-voltage measurements. The anomaly in current–voltage characteristics was related to barrier height inhomogeneity at the interface and modified by the assumption of Gaussian distribution of barrier height, in which mean barrier height and standard deviation at zero bias were found as 2.11 and 0.24 eV, respectively. Moreover, Richardson constant value was determined as 141.95 Acm−2K−2 by means of modified Richardson plot.

Electrical Characterization of In Schottky Contacts to Epitaxial n-In0.46Ga0.54P Grown on n+-GaAs by Mocvd

1996 ◽  
Vol 448 ◽  
Author(s):  
N. Marcano ◽  
A. Singh
Keyword(s):  
Barrier Height ◽  
Thermionic Emission ◽  
Electrical Characterization ◽  
Interface Layer ◽  
Zero Bias ◽  
Current Voltage ◽  
Capacitance Voltage ◽  
Direct Current Voltage ◽  
Etched Surface

AbstractIn/n-In0.46Ga0.54P Schottky diode was fabricated by thermal evaporation of In on chemically etched surface of In0.45Ga0.54P:Si epitaxial layer grown on highly doped n type GaAs. The In metal formed a high quality rectifying contact to In0.46Ga0.54P:Si with a rectification ratio of 500. The direct current-voltage/temperature (I-V/T) characteristics were non-ideal with the values of the ideality factor (n) between 1.26-1.78 for 400>T>260 K. The forward I-V data strongly indicated that the current was controlled by the generation-recombination (GR) and thermionic emission (TE) mechanisms for temperature in the range 260-400 K. From the temperature variation of the TE reverse saturation current, the values of (0.75±0.05)V and the (4.5±0.5)×10-5 Acm-2K-2 for the zero bias zero temperature barrier height (φoo) and modified effective Richardson constant were obtained. The 1 MHz capacitance-voltage (C-V) data for 260 K < T < 400 K was analyzed in terms of the C-2-V relation including the effect of interface layer to obtain more realistic values of the barrier height (φbo). The temperature dependence of φbo was described the relation φbo =(0.86±10.03) - (8.4±0.7)×l0-4T. The values of φoo, obtained by the I-V and C-V techniques agreed well.

Rectifying and Schottky characteristics of a-SixGe1−xOy with metal contacts

2014 ◽  
Vol 92 (7/8) ◽  
pp. 606-610 ◽  
Author(s):  
Md Muztoba ◽  
Mukti Rana
Keyword(s):  
Ohmic Contact ◽  
Infrared Detector ◽  
Schottky Contact ◽  
Thermionic Emission ◽  
Emission Model ◽  
Metal Contacts ◽  
Temperature Changes ◽  
Barrier Heights ◽  
Current Voltage ◽  
Semiconductor Contacts

Metal–semiconductor contacts are a vital part of semiconductor devices as they can form a Schottky barrier or an Ohmic contact. The nature of the contact plays an important role in determining the electrical and physical characteristics of the device and hence is of paramount importance in the operation of the device. In the current work we report the design, fabrication, and current–voltage (I-V) characteristics of microbolometers, a type of infrared detector where the change in temperature changes the resistance of the sensing layer. Eight different types of microbolometers were fabricated using a-SixGe1−x or a-SixGe1−xOy sensing layers and Ti, Cr, Al, Au, Ni, or Ni0.80Cr0.20 metals contacts. It has been observed that bolometers with an a-Si0.15Ge0.85 (Si was lightly p-doped) sensing layer formed a Schottky contact with Ti, Au, Cr, and Al contact metals, while bolometers with a-Si0.15Ge0.85 (Si was heavily n-doped) sensing layers formed an Ohmic contact with Au. For microbolometers with a Si0.15Ge0.85O0.039 sensing layer, both Ni and Ni0.80Cr0.20 contact metals formed the Ohmic contact. For a-SixGe1−x and a-SixGe1−xOy microbolometers, Au and Ni0.80Cr0.20 were used as the absorber layers, respectively. The I–V characteristics of the microbolometers were analyzed with a thermionic emission model. A linear dependence on the Ge composition was approximated to find the effective Richardson constant. The theory predicts Richardson constants of 112 and 50 A/cm2K2 for Si and Ge, respectively. Barrier heights of all devices are calculated and the reasons for the formation of the Ohmic and Schottky contacts are discussed.

scholarly journals On the electrical characteristics of Al/p-Si diodes with and without (PVP: Sn-TeO2) interlayer using current–voltage (I–V) measurements

2020 ◽  
Vol 126 (12) ◽  
Author(s):  
Abbas Sabahi Namini ◽  
Mehdi Shahedi Asl ◽  
Gholamreza Pirgholi-Givi ◽  
Seyed Ali Delbari ◽  
Javid Farazin ◽  
...  
Keyword(s):  
Series Resistance ◽  
Thermionic Emission ◽  
Reverse Current ◽  
Current Transport ◽  
Electrical Characteristics ◽  
Transport Mechanisms ◽  
Electrical Parameters ◽  
Zero Bias ◽  
Current Voltage ◽  
Significant Increment

AbstractThe present study aims to investigate the effect of (PVP: Sn-TeO2) interfacial layer on the electrical parameters of the Al/p-Si diode. For this aim, (Sn-TeO2) nanostructures were developed by the ultrasound-assisted method, and both their electrical and optical characteristics were investigated by XRD, SEM, EDS, and UV–Vis methods. The bandgap of Sn-TeO2 was found as 4.65 eV from the (αhυ)2 vs (hυ) plot. The main electrical parameters of the Al/p-Si diodes with/ without (PVP: Sn-TeO2) interlayer, such as ideality factor (n), zero-bias barrier height (Φ0), and series resistance (Rs), were calculated by applying and comparing two methods of thermionic emission theory and Cheung’s functions. These results show that the presence of the (PVP: Sn-TeO2 interlayer, along with the increase of Φ0, and the decrease of n and Rs, led to a significant increment in the rectification of MPS when compared to MS diode. The current-transport mechanisms (CTMs) of them were examined through the forward LnIF − LnVF and reverse LnIR − VR0.5 bias currents, and then, the Poole–Frenkel and Schottky field-lowering coefficients (β) were calculated and obtained its value from the theoretical and experimental methods showed that the mechanism of the reverse current of MS and MPS diodes is governing by the Schottky emission and Pool-Frenkel mechanism, respectively.

scholarly journals Electrical and Photoconductivity Properties of Al/CdFe2O4/p-Si/Al Photodiode

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Mehmet Çavaş ◽  
Fahrettin Yakuphanoglu ◽  
Savaş Kaya
Keyword(s):  
Barrier Height ◽  
Ideality Factor ◽  
Low Cost ◽  
Strong Dependence ◽  
Sol Gel ◽  
Thermionic Emission ◽  
Emission Model ◽  
Current Voltage ◽  
Coating Method ◽  
Low Cost Manufacturing

In the present study, we have investigated the effects of illumination intensity on the optical and electrical characteristics of the Al/CdFe2O4/p-Si/Al photodiode. A thin film of CdFe2O4 was fabricated using the sol-gel spin coating method that allows good thickness control and low-cost manufacturing as compared to alternative techniques. The current-voltage (I-V) of the Al/CdFe2O4/p-Si/Al photodiode was measured in the dark and under different illumination intensities. The photocurrent increased with higher luminous intensity and its sensitivity has a strong dependence on the reverse bias rising from 1.08⁎10-7 A under dark conditions to 6.11⁎10-4 A at 100 mW/cm2 of illumination. The parameters of the photodiode such as ideality factor and barrier height were calculated using the thermionic emission model. The ideality factor of the Al/CdFe2O4/p-Si/Al photodiode was found to be 4.4. The barrier height was found to be 0.88 eV. The capacitance-voltage (C-V) characteristics measured at different frequencies have strongly varied with frequency, decreasing with frequency. Consequently, the resulting interface density (Dit) value of the Al/CdFe2O4/p-Si/Al photodiode also decreased with higher frequency. Similarly, the fitted series resistance of the Al/CdFe2O4/p-Si/Al photodiode has declined with higher frequency.

scholarly journals Measure and analysis of 4H-SiC Schottky barrier height with Mo contacts

2019 ◽  
Vol 85 (1) ◽  
pp. 10102 ◽  
Author(s):  
Teng Zhang ◽  
Christophe Raynaud ◽  
Dominique Planson
Keyword(s):  
Barrier Height ◽  
Deep Level ◽  
Schottky Contact ◽  
Thermionic Emission ◽  
Distribution Model ◽  
Emission Model ◽  
Height Distribution ◽  
Current Voltage ◽  
Transient Spectroscopy ◽  
Fluctuation Model

Current–voltage (I–V) and capacitance–voltage (C–V) characteristics of Schottky Mo/4H-SiC diodes have been measured and analyzed as a function of temperature between 80 and 400 K. The I–V characteristics significantly deviate from ideal characteristics predicted by the thermionic emission model because of the inhomogeneity of Schottky contact. After a brief review of the different existing models, the main parameters (ideality factor, barrier height, and effective Richardson constant) of both diodes have been extracted in the frame of a Gaussian barrier height distribution model, whose mean and standard deviation are linearly dependent on voltage and temperature, as well as in the context of the potential fluctuation model. The results are compared with the values extracted by C–V and the values in the literature. A link is established between these two models. Diodes of different I–V  characteristics, either identified as single barrier or double barrier, have been analyzed by Deep Level Transient Spectroscopy (DLTS) to investigate the deep level defects present. No noticeable difference has been found.

Two-diode behavior in metal-ferroelectric-semiconductor structures with bismuth titanate interfacial layer

2017 ◽  
Vol 31 (27) ◽  
pp. 1750197 ◽  
Author(s):  
Perihan Durmuş ◽  
Şemsettin Altindal
Keyword(s):  
Conduction Mechanism ◽  
Bismuth Titanate ◽  
Thermionic Emission ◽  
Saturation Current ◽  
Electrical Parameters ◽  
Zero Bias ◽  
Semiconductor Structures ◽  
Current Voltage ◽  
Diode Behavior ◽  
Increasing Temperature

In this study, electrical parameters of the Al/Bi4Ti3O[Formula: see text]/p-Si metal-ferroelectric-semiconductor (MFS) structure and their temperature dependence were investigated using current–voltage (I–V) data measured between 120 K and 300 K. Semi-logarithmic I–V plots of the structure revealed that fabricated structure presents two-diode behavior that leads to two sets of ideality factor, reverse saturation current and zero-bias barrier height (BH) values. Obtained results of these parameters suggest that current conduction mechanism (CCM) deviates strongly from thermionic emission theory particularly at low temperatures. High values of interface states and nkT/q[Formula: see text]−[Formula: see text]kT/q plot supported the idea of deviation from thermionic emission. In addition, [Formula: see text](I)[Formula: see text]−[Formula: see text][Formula: see text](V) plots suggested that CCM varies from one bias region to another and depends on temperature as well. Series resistance values were calculated using Ohm’s law and Cheungs’ functions, and they decreased drastically with increasing temperature.

1/f Noise in Ti–Au/n-Type GaAs Schottky Barrier Diodes

2015 ◽  
Vol 14 (03) ◽  
pp. 1550029 ◽  
Author(s):  
Alexey V. Klyuev ◽  
Arkady V. Yakimov ◽  
Irene S. Zhukova
Keyword(s):  
Schottky Barrier ◽  
Field Emission ◽  
Thermionic Emission ◽  
Low Frequency ◽  
Schottky Barrier Diodes ◽  
Transport Mechanisms ◽  
Current Dependence ◽  
Current Voltage ◽  
Thermionic Field Emission ◽  
Multiple Charge

We have studied the forward current–voltage (I–V) characteristics of Ti–Au /n-type GaAs Schottky barrier diodes. However, we found some anomalies in I–V characteristics. Hence, we have considered a model that incorporates thermionic emission, thermionic-field emission and leakage components. Leakage component is linear and visible at rather small currents. The anomalies observed in the diode parameters were effectively construed in terms of the contribution of these multiple charge transport mechanisms across the interface of the diodes. It is shown that thermionic-field emission and leakage are the sources of low-frequency (1/f) noise in such type of diodes. Various Schottky diode parameters were also extracted from the I–V characteristics and current dependence of spectrum of 1/f voltage noise.

A Study of Co and Mn in ZnO Varistors

1985 ◽  
Vol 46 ◽  
Author(s):  
G. E. Pike ◽  
C. H. Seager ◽  
R. G. Dosch
Keyword(s):  
Impact Ionization ◽  
Polycrystalline Materials ◽  
Photoluminescence Spectra ◽  
Photothermal Deflection Spectroscopy ◽  
Linear Current ◽  
Current Voltage ◽  
Zno Varistors ◽  
Current Voltage Characteristics ◽  
Photothermal Deflection ◽  
Absorption Features

AbstractZnO varistors are polycrystalline materials which have highly non—linear current/voltage characteristics controlled by depletion regions around the grain boundaries. Dissolved transition metals at concentrations of about 1 at.% are required to achieve this large nonlinearity, but their role is unclear. To address this issue we have usedthe technique of photothermal deflection spectroscopy to measure the optical absorption of varistors containing Co or Mn, both common dopants. Prominent peaks and edges appear in the spectra, and are associated with substitutional Co2+and Mn2+ ions whose ground states are deep within the ZnO bandgap. Electro— and photoluminescence spectra show Stokes shifted peaks for some of these transitions. The spectral dependence of the photoconductivity shows that some of the absorption features correspond to ionization of the impurities. This result is used to show how the dark impact ionization of these impurities due to a high applied voltage can contribute to the current/voltage nonlinearity.

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