Cheung's Method Research Articles

Investigation, analysis and comparison of current-voltage characteristics for Au/Ni/GaN Schottky structure using I-V-T simulation

Abstract In this work, we have presented a theoretical study of Au/Ni/GaN Schottky diode based on current-voltage (I-V) measurement for temperature range of 120 K to 400 K. The electrical parameters of Au/Ni/GaN, such as barrier height (Φb), ideality factor and series resistance have been calculated employing the conventional current-voltage (I-V), Cheung and Chattopadhyay method. Also, the variation of Gaussian distribution (P (Φb)) as a function of barrier height (Φb) has been studied. Therefore, the modified ( ( ln ⁡ ( I 0 T 2 ) − ( q 2 σ s 0 2 2 kT 2 ) = ln ⁡ ( AA * ) − q ∅ B 0 kT ) vs . ( 1 kT ) ) ( {( {\ln \left( {{{{\rm{I}}_0 } \over {{\rm{T}}^2 }}} \right) - \left( {{{{\rm{q}}^2 \sigma _{{\rm{s}}0}^2 } \over {2{\rm{kT}}^2 }}} \right) = \ln ( {{\rm{AA}}^*} ) - {{{\rm{q}}\emptyset_{{\rm B}0} } \over {{\rm{kT}}}}} ){\rm{vs}}.( {{1 \over {{\rm{kT}}}}} )} ) relation has been extracted from (I-V) characteristics, where the values of ΦB0 and A Simul * {\rm{A}}_{{\rm{Simul}}}^* have been found in different temperature ranges. The obtained results have been compared to the existing experimental data and a good agreement was found.

Improved barrier parameters and working stability of Au/p-GO/n-lnP/Au–Ge Schottky barrier diode with GO interlayer showing resistive switching effect

In this study, Au/p-GO/n-lnP/Au–Ge device structure for possible micro- and opto-electronic applications has been investigated. Firstly, the graphene oxide (GO) interlayer has been characterized before device fabrication. The GO interlayer has band gap energy of 2.4 eV and large contact area. In the Raman spectrum, ID/IG ratio was determined as 0.78. According to the Thermionic, Norde and Cheung methods, ideality factor, Schottky barrier height, series resistance and distribution of interface states have been investigated for the devices. The presence of GO interlayer has caused to both the barrier height increased from 0.44 to 0.71 eV and the significant increase in rectification ratio from 102 to 105 at ±1 V. Additionally, the ideality factor has improved from 1.32 to 1.23 at 300 K. The device working stability at high temperatures (400 K) has been observed in the Au/p-GO/n-lnP/Au–Ge device. Furthermore, the resistive switching effect of the GO interlayer has been observed as temperature-dependent metallic character of series resistance in high voltage region.

Temperature dependent current-voltage characteristics of Al/TiO2/n-Si and Al/Cu:TiO2/n-Si devices

We fabricated undoped and Cu doped TiO2 thin films by spin coating technique and employed the films as interfacial oxide layer between the Al and n-type Si to investigate the effect of temperature on the Al/TiO2/n-Si and Al/Cu:TiO2/n-Si devices. For that aim, the I–V measurements were performed in the range of 50 K–400 K by 50 K interval. The devices exhibited good rectifying behavior and thermal response in a wide range temperature. Ideality factor, barrier height and series resistance were calculated from I–V measurements for various temperatures by thermionic emission theory, Norde and Cheung methods and discussed in the details. The obtained results revealed that the device parameters are a strong function of the temperature. The interface states (Nss) were affected by the changing of the temperatures. The Al/TiO2/n-Si and Al/Cu:TiO2/n-Si devices can be performed for wide range temperatures in various technological applications.

Methyl red/ indium-tin-oxide organic diode: An electrical and optoelectronic study

Methyl red / indium-tin-oxide (ITO) organic diode is fabricated by simple, low cost solution drop casting method. Using the conventional Tauc method, the optical bandgap of methyl red is calculated 2.23 eV from the measured absorbance data. The electrical analyses of methyl red/ITO structure are carried out based on the thermionic emission model of Schottky barrier diode. The ideality factor, barrier height and series resistance are calculated using the standard method (5.40, 0.88 eV, 106 Ω), Bohlin's method (5.20, 0.87 eV, 1.5 × 106 Ω) and Cheung's method (4.88, 0.85 eV, 9 × 106 Ω) and the values of such parameters are in close agreement. In the optoelectronic study, a considerable improvement in photocurrent under steady illumination reveals a substantial photosensitivity of the device. The diode is also proved as a stable photo-switch owing to its fine photo absorbing quality. The photo response of the test structure is attributed to the presence of methyl red over layer and the phenomena is ascribed by the delocalization of π electrons from the conjugated structure between the benzene and azo groups of methyl red.

Rectifying Characteristics of Thermally Treated Mo/SiC Schottky Contact

The rectifying characteristics of a Mo/SiC Schottky contact fabricated by facing targets sputtering system were investigated through current–voltage measurement. The Schottky diode parameters were extracted from the forward current–voltage characteristic curve by the Cheung and Cheung method and the Norde method. The as-deposited Mo/SiC Schottky contacts possessed Schottky barrier heights of 1.17 and 1.22 eV, respectively. The Schottky barrier heights of the diodes were decreased to 1.01 and 0.91 eV after annealing at 400 °C for 30 min. The ideality factor was increased from 1.14 and 1.08 to 1.51 and 1.41, respectively. This implies the presence of non-ideal behaviors due to a current transport mechanism other than ideal thermionic emission, and the non-ideal behaviors increased as a result of excessive thermal annealing. In contrast, only a negligible change was observed in the crystallographic characteristics. This result suggests that the reason for the deviation from the ideal rectifying characteristics of the Mo/SiC Schottky contact through the annealing process was the variation in the current transport mechanism, including recombination, tunneling, and/or minority carrier injection.

A New Parameter Extraction Method for Schottky Barrier Diodes

A new parameter extraction method for Schottky barrier diodes is provided in this paper. Since the current model of Schottky barrier diodes is a nonlinear self-consistent equation, the nonlinear inconsistent equations set is composed of nonlinear model equations under different biases. The problem of solving nonlinear inconsistent equations set is transformed into an optimization problem. The global optimal solution of the parameters is obtained by genetic algorithm. Comparing with experimental data, the results indicate that the error of the method proposed by this paper is lower than that of Cheung method.

Investigation on Transition Diode Properties of rGO‐GO/n‐Si Heterojunction

Thermal annealing in the range of 100–700 °C is applied to reduce the graphene oxide (GO) film into reduced‐GO (rGO). Raman spectrum analysis and film conductivity analysis via Hall measurement confirms the advancement of reduction degree at higher annealing temperature (AT). The film conductivity is 19.7 S cm−1 after annealing at 700 °C. Hall measurement also reveals the sudden appearance of electron conduction around 300 °C. The type of attached oxygen functional groups determines the type of majority carrier in the film and modulate the work function of conductive crystalline sp2 carbon. Then, the effect of AT to the current‐voltage characteristics of n‐type silicon/GO junction are discussed. The fabricated junction is analyzed based on Schottky junction operation using Rhoderick and Cheung methods. The higher reduction degree leads to lower series resistance. Schottky barrier height is found to increase to 0.92 eV for AT around 300 °C, before it decreases at higher AT. Correlation between the barrier height and the hole concentration from Hall measurement can be noticed. Schottky junction with AT of 400 °C gives the highest rectification ratio of 149, owing to moderate value of series resistance as well as high barrier height.

Fermi level depinning in Ti/n-type Ge Schottky junction by the insertion of fluorinated graphene

The effect of fluorinated graphene (f-Gr) as the interfacial layer on Fermi level depinning in Ti/n-type Ge Schottky barrier diodes (SBDs) is intensively studied. Electrical properties of the SBDs are characterized by I-V method. The series resistance, barrier height and ideal factor of the SBDs are extracted by forward I-V, Cheung's method and Norde's method, respectively. Fluorinated graphene is found effective in reducing barrier height of Ti/Ge SBD. On the contrary, the SBD with graphene interlayer shows the increased barrier height and the barrier height changes significantly with bias voltage due to graphene induced Fermi level shift. Therefore, the fluorinated graphene is more stable and predictable in modifying metal/semiconductor interfaces, which can be further used in other metal/semiconductor contacts to achieve high quality SBDs.

Electrical characteristics analyses of zinc-oxide based MIS structure grown by atomic layer deposition

The ZnO films are grown on the p-type Si for metal-insulator-semiconductor (MIS) type Schottky barrier diode (SBHS) fabrication by atomic layer deposition (ALD) method. The electrical characteristics of the three diodes called as D1, D2 and D3 have been investigated. The surface characteristics and thin film in structure were detected by secondary ion mass spectrometry (SIMS) and atomic force microscopy (AFM). The current-voltage (I–V) properties of Al/ZnO/p-Si structures were analyzed in the dark at room temperature. The electrical specifications such as, barrier height (ϕb) ideality factor (n) and series resistance (Rs) of these structures were examined by Norde’s function, Cheung method and thermionic emission (TE) theory. Barrier height values computed from Cheung and I–V method was found to be different from each other. Interface state density (Dit) of these structures was studied using the I–V properties. The non-ideal behavior of measured characteristics advised the presence of interface conditions. The acquired results imply that the fabricated diodes can be used for NIR Schottky photo detector applications.

Effect of single walled carbon nanotubes on series resistance of Rose Bengal and Methyl Red dye-based organic photovoltaic device

The influence of single walled carbon nanotube (SWCNT) on the series resistance (Rs) of Rose Bengal (RB) and Methyl Red (MR) dye-based organic diodes has been studied. It has been revealed from experimental results that SWCNT has a significant effect on Rs. The values of Rs are measured from current–voltage (I–V) characteristics and also by utilizing the Cheung method. Obtained values from the Cheung method have been verified using H(I)–I plots for all dye-based devices. The extracted values using these two processes show a good consistency with each other. It is observed that Rs is reduced significantly by incorporating SWCNT for both dyes. The estimated amounts of reduction of Rs using SWCNT are 76.08% and 64.23% obtained from the I–V relationship whereas the value of Rs shows a reduction of 83.5% and 67.1% when measured by using the Cheung method for RB and MR dyes respectively. The ideality factor and barrier height of the diodes have also been extracted. The ideality factor has decreased with incorporation of SWCNT. A reduction in barrier height for the devices has also been observed in the presence of SWCNT.

Characterization of Al/In:ZnO/p-Si photodiodes for various In doped level to ZnO interfacial layers

The detection of the light by a device is so important for industrial applications such as energy harvesting, sensing and switching. For that aim, we have introduced various In doped (0%, 0.1%, 0.5% and 1.0%) nanostructure ZnO thin films which was prepared by the sol-gel spin coating technique as interfacial materials between the Al metal and p-type Si for investigation photodetection properties of the material. According to morphological results of the In doped ZnO thin films at AFM, undoped and In doped ZnO thin films formed as fiber like structures. The obtained optical band gap energy for undoped, 0.1%, 0.5% and 1.0% In doped ZnO thin films were determined as 3.293 eV, 3.283 eV, 3.272 eV and 3.263 eV, respectively. The Al/In:ZnO/p-Si devices were characterized with I–V and C–V measurements. The I–V data was acquired under various illumination conditions to see the response of the devices to the light. The I–V characteristics have revealed that the devices have high ideality factors and, their values usually increased with increasing In doping level, but the rectifying properties decreased. In addition, barrier heights and series resistance values decreased with increasing In doping level. Also, the device parameters were calculated via Cheung and Norde methods for accuracy of the results. The current transient measurements highlighted that In doping provided to increase of light response. The C–V measurements have imparted that the capacitance values are strong function of the frequency and voltage for various In doping level. The devices can be thought and improved as photodiode and photodetector applications in the industry.

Performance analysis of Schottky diodes based on Bi doped p-ZnO thin films

In the present paper, Bismuth (Bi) doped ZnO thin film have been deposited using sol gel spin coating technique to produce p-type ZnO films on n-Si substrate. The deposited Bi doped ZnO thin films were characterized using X-ray diffraction (XRD), atomic force microscopy (AFM), hot point probe and hall measurement. The XRD and AFM characterization results shows uniform growth of the film over the entire substrate having polycrystalline nature of the film and Hall measurement and hot point probe method shows p-type nature of the deposited Bi doped ZnO film. Further, Palladium (Pd) and Nickel (Ni) metal contacts have been deposited over separate Bi doped ZnO thin films using vacuum coating method to fabricate Schottky diodes. The current–voltage characteristics have been analyzed by using conventional thermionic emission model, Cheung's method and Norde's technique to calculate the barrier height, ideality factor and series resistance of the fabricated Schottky diodes. From the calculations, it is observed that Cheung's method gives more realistic results for estimating diode parameters.

Electrical Characterizations of ZnO-Based MOS-Type Schottky Barrier Diodes

The electrical properties of Al/ZnO/p-Si MOS (metal-oxide semiconductor)-type Schottky barrier diodes have been investigated in this study. ZnO layer on p-type Si (111) substrate was deposited by evaporation technique. The two contacts were constructed as one top and one bottom contacts. Al rectifying contacts was formed on the top of ZnO layer. Al ohmic contact was formed the back surface of the Si wafer. The current-voltage (I-V) characteristics of Al/ZnO/p-Si diodes were measured at room temperature and in the dark. The main electrical parameters of Al/ZnO/p-Si MOS-type structures, such as the ideality factor (n), barrier height ( ) and series resistance (Rs) have been analyzed and calculated from current-voltage (I-V) characteristics by using thermionic emission theory and Cheung method

Optoelectrical properties of Al/p-Si/Fe:N doped ZnO/Al diodes

In this work, 3% Fe doped zinc oxide (ZnO) doped by Nitrogen thin films were grown by reactive radio frequency magnetron sputtering on p-Si substrates. The structural and optical properties of the 3% Fe doped ZnO doped by Nitrogen thin films were investigated by the scanning electron microscope and spectrophotometry. The diodes with the configuration of Al/p-Si/3% Fe-ZnO:N/Al have been fabricated and it has been observed that the diodes exhibit a good rectification. The optical band gap was found to be 3.98 ± 0.02 eV for 3% Fe doped ZnO:N thin film deposited at the N2 flow rate of 15 sccm. The electrical parameters of the diode were determined using Cheung's and Norde's method. The capacitance–voltage and conductance–voltage characteristics of Al/p-Si/3% Fe-ZnO:N/Al structure have been investigated in the frequency range 10 kHz–1 MHz. The increase in capacitance at lower frequency is attributed to the density of interface states. It is evaluated that the prepared diodes can be used as nanoscale electronic and optoelectronic devices.

Shunt resistance and saturation current determination in CdTe and CIGS solar cells. Part 2: application to experimental IV measurements and comparison with other methods

In this Part 2 of this series of articles, the procedure proposed in Part 1, namely a new parameter extraction technique of the shunt resistance (Rsh) and saturation current (Isat) of a current-voltage (I–V) measurement of a solar cell, within the one-diode model, is applied to CdS-CdTe and CIGS-CdS solar cells. First, the Cheung method is used to obtain the series resistance (Rs) and the ideality factor n. Afterwards, procedures A and B proposed in Part 1 are used to obtain Rsh and Isat. The procedure is compared with two other commonly used procedures. Better accuracy on the simulated I–V curves used with the parameters extracted by our method is obtained. Also, the integral percentage errors from the simulated I–V curves using the method proposed in this study are one order of magnitude smaller compared with the integral percentage errors using the other two methods.

Shunt resistance and saturation current determination in CdTe and CIGS solar cells. Part 1: a new theoretical procedure and comparison with other methodologies

A new proposal for the extraction of the shunt resistance (Rsh) and saturation current (Isat) of a current-voltage (I–V) measurement of a solar cell, within the one-diode model, is given. First, the Cheung method is extended to obtain the series resistance (Rs), the ideality factor (n) and an upper limit for Isat. In this article which is Part 1 of two parts, two procedures are proposed to obtain fitting values for Rsh and Isat within some voltage range. These two procedures are used in two simulated I–V curves (one in darkness and the other one under illumination) to recover the known solar cell parameters Rsh, Rs, n, Isat and the light current Ilig and test its accuracy. The method is compared with two different common parameter extraction methods. These three procedures are used and compared in Part 2 in the I–V curves of CdS-CdTe and CIGS-CdS solar cells.

Interface State Density and Series Resistance of n-Type Nanocrystalline FeSi₂/p-Type Si Heterojunctions Formed by Utilizing Facing-Target Direct-Current Sputtering.

n-Type nanocrystalline FeSi2/p-type Si heterojunctions were formed by using facing-target direct- current sputtering at room temperature. The J-V characteristic results revealed that the reverse leakage current is large and the response under illumination of near-infrared light is very weak. The capacitance-voltage-frequency (C-V-f) and conductance-voltage-frequency (G-V-f) measurements were carried out at room temperature in order to estimate the series resistance (Rs) by using the Nicollian-Brews method and the density of interface state (Nss) by using the Hill-Coleman method. By estimation according to the Nicollian-Brews method, the Rs value increases with decreasing f value. The Rs values at zero bias voltage were 2.07 Ω at 60 kHz and 1.54 Ω at 2 MHz, which are consistent with those calculated by using the Cheung's and Norde's methods. The obtained Rs should be attributable to the Rs existing in the ohmic contact and neutral regions, which is the current-limiting factor for junctions. The nss values calculated by using the Hill-Coleman method were 2.70 × 1014 eV-1cm-2 at 60 kHz and 1.43 × 1013 eV-1cm-2 at 2 MHz. This result revealed the presence of interface states at the hetero-interface behaving as a leakage current center and a trap center of the photo-generated carrier, which degraded the junction properties at room temperature.

Schottky junction interfacial properties at high temperature: A case of AgNWs embedded metal oxide/p-Si

Studying the performance limiting parameters of the Schottky device is an urgent issue, which are addressed herein by thermally stable silver nanowire (AgNW) embedded metal oxide/p-Si Schottky device. Temperature and bias dependent junction interfacial properties of AgNW-ITO/Si Schottky photoelectric device are reported. The current−voltage−temperature (I−V−T), capacitance-voltage-temperature (C−V−T) and impedance analysis have been carried out in the high-temperature region. The ideality factor and barrier height of Schottky junction are assessed using I−V−T characteristics and thermionic emission, to reveal the decrease of ideality factor and increase of barrier height by the increasing of temperature. The extracted values of laterally homogeneous Schottky (ϕb) and ideality factor (n) are approximately 0.73 eV and 1.58, respectively. Series resistance (Rs) assessed using Cheung's method and found that it decreases with the increase of temperature. A linear response of Rs of AgNW-ITO/Si Schottky junction is observed with respect to change in forward bias, i.e. dRS/dV from 0 to 0.7 V is in the range of 36.12–36.43 Ω with a rate of 1.44 Ω/V. Impedance spectroscopy is used to study the effect of bias voltage and temperature on intrinsic Schottky properties which are responsible for photoconversion efficiency. These systematic analyses are useful for the AgNWs-embedding Si solar cells or photoelectrochemical cells.

Comparison of Graphene and Zinc Dopant Materials for Organic Polymer Interfacial Layer Between Metal Semiconductor Structure

Au/n-GaAs structures with polyvinyl alcohol (PVA) organic interface layer were produced by doping graphene (Gr) and zinc (Zn) separately to the interface layer. The electrical characterizations of both structures which have Schottky barrier diodes (SBDs) property were compared both at the forward and reverse biases at room temperature using the current-voltage (I-V) data. For this purpose, the main electrical parameters such as saturation current (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> ), barrier height (Φ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Bo</sub> ), ideality factor (n), series (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> ) resistance, and shunt (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sh</sub> ) resistance are obtained for Gr doped and Zn doped Au/PVA/n-GaAs and compared by utilizing thermionic emission theory, Cheung's method and modified Norde's methods. Investigation of R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> and R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sh</sub> values at (±2 V) for Gr-doped and Zn-doped structures ensured to obtain the rectifiying ratio values and give an idea to find out the better quality of these structures. Thus, the results for the comparison of polymer interlayers with different dopants show that doping with both Zn and Gr differently improved the quality of SBDs when considering the main electrical parameters.

Electrodeposition of Si–DLC nanocomposite film and its electronic application

In this study, a silicon doped diamond-like carbon (DLC) nanocomposite film was deposited electrochemically and it was used to fabricate an Ag/Si–DLC/p-Si metal–interlayer–semiconductor (MIS) Schottky diode. Methanol (CH3OH) was used as carbon and tetraethoxysilane (Si(OC2H5)4) as Si source, respectively. Morphology of the film was observed by scanning electron microscopy and continuous surface with numerous lumps spread randomly was observed. Structural and chemical composition analyses of the film were carried out by Raman and X-ray photoelectron spectroscopy. Typical D and G bands of DLC films were not observed in the Raman spectrum due to abundance of Si–C bonds. Silicon incorporation promoted the film deposition and increased sp3 bonds in the film. Current–Voltage (I–V) measurement was conducted to obtain parameters of the MIS diode. The diode exhibited a good rectifier behavior with ~ 103 rectification ratio. In the forward bias semi-logarithmic I–V plot, two linear regions with different slopes were observed. Such behavior was modelled by two parallel diodes and attributed to different conduction mechanism. The main electrical parameters, such as barrier height, ideality factor and series resistance were calculated by I–V and Cheung–Cheung methods. The Si–DLC nanocomposite film acted as barrier height modifier in the MIS diode.