Cheung Functions Research Articles

Ru/Ti Schottky Contacts on N-type In-P (100): Temperature Dependence of Current-Voltage (I-V) Characteristics

The current-voltage characteristics (I-V) of Ru/Ti/n-InP (100) schottky diodes have been measured in the temperature range of 200-400oC. These are analyzed using thermionic emission theory (TE) by incorporating the concept of barrier inhomogeneity at the metal/semiconductor interface through a Gaussian distribution factor. The forward and reverse I-V characteristics are analyzed to estimate the Schottky barrier parameters. It has revealed that decrease of barrier height and increase of ideality factor as the temperature increases. The barrier height (Фb) is found to be 0.82eV, 0.81eV, 0.80eV and 0.79eV for as-deposited sample, annealed at 200oC, 300oC and 400oC respectively. The ideality factor in the same temperature range are found to be 1.19, 1.26, 1.59, 1.64 and this is good agreement with the Cheung's function dV/dln(I) vs. I. The series resistance values are evaluated in the range of 16MΩ – 62 MΩ with increasing temperature. The nonlinearity in the Richardson plot and Schottky barrier heights may be attributed to the formation of phosphide phases at the Ru/Ti/n-InP interface.

Junction properties and conduction mechanism of new terbium complexes with triethylene glycol ligand for potential application in organic electronic device

Terbium-picrate triethylene glycol (EO3-Tb-Pic) complex was prepared in thin film and single layer device structure of ITO/EO3-Tb-Pic/Al, using spin coating technique. The UV-Vis absorption spectroscopy analysis was performed to evaluate the electronic molecular transition of the complex. The optical band gap, Eg estimated from the Tauc model revealed that EO3-Tb-Pic thin film exhibited a direct transition with Eg of 2.70 eV. The electronic parameters of the ITO/EO3-Tb-Pic/Al device such as the ideality factor n, barrier height Φb, saturation current Io, and series resistance Rs, were extracted from the conventional lnI-V, Cheung's functions and Norde's method. It was found that the evaluated parameters calculated from Norde's and Cheung's methods were consistent with those calculated from the conventional I-V method. In the double logarithmic I-V plot, three distinct regions based on the slope were identified, and the conduction mechanisms were discussed and explained. The mobility, μ value was estimated from SCLC region as 2.58×10−7 cm2/(V·s). This newly obtained lanthanide complex may be potentially utilized in electronic devices.

Electrical characteristics of organic/inorganic Pt(II) complex/p-Si semiconductor contacts

We produced Pt(II) complexes using the bidentate ligand N-aminopyrimidine-2-thione (APTH). The optical transmission of thin Pt-APTH films was measured. The optical bandgap of the material was 2.58eV. With the expectation that it might have semiconductor properties and that the Pt-APTH complex might exhibit rectifier behavior when brought into appropriate contact with a semiconductor, we fabricated Pt-APTH/p-Si contacts by direct addition of a solution of Pt-APTH to the front side of p-Si wafers. Forward bias current–voltage measurements revealed satisfactory rectifying behavior for the Pt-APTH/p-Si contacts, with a mean rectification ratio of 4.40×102 and a mean barrier height of 0.765eV. Cheung and Norde functions were used to obtain and verify some electrical characteristics of the contacts. The results obtained from both methods are compared and discussed.

Electronic parameters and carrier transport mechanism of high-barrier Se Schottky contacts to n-type GaN

The electrical properties and current conduction mechanism of high-barrier Se/n-GaN Schottky diode have been investigated for the first time by current–voltage (I–V) and capacitance–voltage (C–V) measurements. High resolution transmission electron microscopy (HRTEM) results confirmed that no reaction occurs between Se film and the GaN substrate during Se deposition. Investigations reveal that the contact exhibited an excellent rectification behavior. The estimated barrier height of Se/n-GaN Schottky contact is 0.92eV (I–V) and 1.27eV (C–V) with the ideality factor of 1.10. The barrier height and series resistance are extracted by Cheung's functions. It is observed that the series resistance values obtained from Cheung's functions is in good agreement with each other. Further, capacitance–voltage measurements of the Se/n-GaN Schottky diode are carried out at different frequencies. The discrepancy between Schottky barrier heights obtained from I–V and C–V measurements is also explained. The AFM results showed that the surface morphology of the Se Schottky contacts on n-GaN is fairly smooth. The forward bias current transport mechanism of the Se/n-type GaN Schottky diode is determined by the log–log plot of I–V characteristics. Investigations reveal that the Schottky emission mechanism is found to be dominant in the reverse bias region of Se/n-GaN Schottky diode.

Electrical properties and interface state energy distributions of Cr/n-Si Schottky barrier diode

In this study, the electrical characteristics of the Cr/n-type Si (MS) Schottky barrier diode have been investigated by the current–voltage (I–V) and capacitance–voltage (C–V) measurements at 300K temperature. Using the thermionic emission theory, the values of ideality factor and the barrier height have been obtained to be 1.22, 0.71 and 1.01, 0.83eV, from the results of the I–V and C–V measurements, respectively. The barrier height (Φb) and the series resistance (RS) obtained from Norde’s function have been compared with those obtained from Cheung functions, and a good agreement between the results of both methods was seen. The interface state density (NSS) calculated without the RS is obtained to be increasing exponentially with bias from 2.40×1012cm−2eV−1 in (EC−0.623) eV to 1.94×1014cm−2eV−1 in (EC−0.495) eV, also, the NSS obtained taking into account the RS has increased exponentially with bias from 2.07×1012cm−2eV−1 to 1.47×1014cm−2eV−1 in the same interval.

I–V–T (current–voltage–temperature) characteristics of the Au/Anthraquinone/p-Si/Al junction device

Abstract The current–voltage measurements of the Au/Anthraquinone/p-Si/Al junction device have been carried out in the temperature range of 80–280 K. It has been observed that the anthraquinone film increases the effective barrier height of the Au/p-Si/Al by influencing the space charge region of p-Si from 0.77 eV to 0.85 eV at 280 K. The current–voltage measurements of the Au/Anthraquinone/p-Si/Al junction device show a decrease of the barrier height and an increase in the ideality factor at low temperatures. The dependence of the ideality factor and barrier height on temperature has been attributed the spatial inhomogeneity in the interface. The non-linearity behavior has been seen in the Richardson plots and the values of activation energy ( E a ) and the Richardson constant ( A ∗ ) has been determined as 0.08 eV and 3.19 × 10 −8 A cm −2 K −2 from the slope and the intercept at ordinate of the linear region of Richardson plot, respectively. The values of the series resistance obtained from Cheung functions are strongly temperature-dependent.

Controlling of conduction mechanism and electronic parameters of silicon–metal junction by mixed Methylene Blue/2′-7′-dichlorofluorescein

Al/p-Si junction based on Organic Mixed Layer (OML) Methylene Blue (MB) and 2′-7′-dichlorofluorescein (DCF) was fabricated and the current–voltage (I–V) and the capacitance–voltage measurements of the structure have been obtained at room temperature. This combination resulted in both a good rectifying behavior and low leakage current. The characteristic parameters of the structure such as barrier height, ideality factor, interface states density and series resistance were determined from the electrical measurements. Also, Cheung functions and Norde method were used to evaluate the I–V characteristics and to obtain the characteristic parameters of the Schottky contact. High-low frequency capacitance–voltage characteristics have been observed to have a maximum. The maximum value of the capacitance is decreased with increasing frequency. The higher values of capacitance at low frequencies were attributed to interface states and the excess capacitance resulting from the interface states in equilibrium with the Si that can follow the alternating current signal. The J–V curves in the reverse direction are taken and interpreted via both Schottky and Poole–Frenkel effects. Poole–Frenkel effect was found to be dominant in the reverse direction.

Perylene diimide: Synthesis, fabrication and temperature dependent electrical characterization of heterojunction with p-silicon

A novel, n-type, organic semiconductor N-Butyl-N′-(6-hydroxyhexyl)perylene-3,4,9,10-tetracarboxylic acid diimide (N-BuHHPDI) has been successfully synthesized in high yield. The compound has been characterized by atomic force microscopy (AFM) to understand the morphological properties of a new n-type organic semiconducting material. A 120nm thin film of N-BuHHPDI has been sandwiched between Al and p-Si to form Al/N-BuHHPDI/p-Si device using the vacuum thermal evaporation technique. The electrical properties of sandwich type Al/N-BuHHPDI/p-Si device have been investigated. The current voltage (I–V) characteristics of the device, in dark, have been measured in the temperature range of 300–330K. At room temperature, the device exhibits rectifying behavior with a rectification ratio of 51.5 at ±6.8V. The device parameters such as ideality factor, barrier height, series and shunt resistances have been extracted using the conventional I–V characterization method. The effect of temperature on these parameters is also studied. Alternative electrical characterization methods such as Cheung's functions and Norde's techniques have been employed to measure the device parameters for comparison. The conduction mechanisms are investigated through the interface of N-BuHHPDI and p-Si.

The Electrical Characteristics of ZnO :Ga/p-Si Junction Diode

ABSTRACTThe junction characteristics between ZnO:Ga (GZO) film and p-Si substrate are discussed in the research. For the transparent semiconductor ZnO, the element Ga is chosen to be the dopant source to produce a high quality n-type ZnO thin film. The ZnO:Ga (GZO) film shows a average transmittance is 84.7% (above 400 nm), a bandgap energy of 3.37 eV, a carrier concentration of 7.29×1013 cm−3and a resistivity of 118 Ω-cm. For the GZO/p-Si junction, it shows a junction barrier height of 0.54 eV with an ideality factor of 1.24. The capacitance-voltage measurement shows that it has a uniform reverse bias depletion layer. The Cheung function is also brought to discussion the diode characteristics.

Electrical characterization of Cr Schottky contacts on undoped and Ni-doped p-ZnO films grown by pulsed laser deposition on Si (100) substrates

Wide band gap semiconducting layers of undoped and Ni-doped p-type ZnO thin films were developed on (100) silicon substrates by pulsed laser deposition (PLD) at a constant oxygen partial pressure of 1.0x10^-^4 Torr and at constant temperature of 250^oC. The electrical properties of the films were studied by resistivity and Hall coefficient measurements at room temperature. P-type conductivity was found to be dominant in these films at room temperature although the incorporation of Ni dopants caused a reduction in the p-character of ZnO films. The surface morphology of the films was evaluated by contact mode atomic force microscopy (AFM) in air. Cr-Schottky contacts were deposited on these p-type ZnO films, and the rectifying properties of the contacts were evaluated. The current-voltage (I-V) characteristics of the Cr/ZnO Schottky diodes were measured at room temperature. Due to series resistance, the Cheung and Cheung functions were used to determine the barrier height and ideality factor of the diodes while Norde function was used to determine barrier height. Ideality factors of 1.07 and 1.22 were obtained for the Cr/undoped ZnO and Cr/Ni-doped ZnO diodes, respectively, while the barrier height was 0.59eV by the Norde model, and in good agreement with 0.62eV of the Cheung-Cheung model, for both undoped and Ni-doped samples.

Ag contact on sol–gel processed MgZnO film

The contact characteristics of Ag on a sol-gel processed MgZnO thin film is presented in the paper. Both of the material properties of the sol-gel ZnO films and the electrical characteristics of the Schottky diode are addressed in the paper. The structure of the MgZnO film is confirmed by X-ray diffraction analysis and the MgZnO film exhibits a hexagonal wurtzite-type polycrystalline. The optical bandgap of the film is determined by using transmittance spectra and is found to be 3.42eV. The Ag/MgZnO diode shows a barrier height of 0.78eV with an ideality factor value of 1.21 and a reverse current of 3.39x10^-^4A/cm^2 at -3V. The Cheung's function is also used to determine the parameters of the diode. The series resistance with a value of 1.38x10^[email protected] is evaluated.

Temperature Dependency And Current Transport Mechanisms Of Pd/V/n-type InP Schottky Rectifiers

We have investigated the temperature-dependent current-voltage (I-V) and capacitance-voltage (C-V) characteristics of Pd/V Schottky contacts on n-type InP in the temperature range of 200-400 K. The estimated barrier height for the Pd/V/n-type InP SBDs from the I-V and C-V characteristics have varied from 0.48 eV to 0.65 eV (I-V) and 0.85 eV to 0.69 eV (C-V), and the ideality factor (n) from 4.87 to 1.58 in the temperature range 200 to 400 K. It has been observed that the ideality factor decreases while the barrier height increases with increase of temperature. Such behaviour is attributed to barrier inhomogeneities by assuming a Gaussian distribution of barrier heights at the interface. Further, it is found that the series resistance (RS) values of Pd/V/n-InP Schottky diode estimated from Cheung's function are strongly temperature dependent. The zero-bias barrier height bo versus 1/2kT plot has been drawn to obtain the evidence of a Gaussian distribution of the barrier

Annealing effects on electrical, structural, and surface morphological properties of Ir/n‐InGaN Schottky structures

AbstractThe effects of thermal annealing on electrical and structural characteristics of iridium (Ir) Schottky contacts to n‐type InGaN have been studied using current–voltage (I–V), capacitance–voltage (C–V), secondary ion mass spectrometer (SIMS), and X‐ray diffraction (XRD) measurements. Measurements showed that the Schottky barrier height (SBH) of as‐deposited sample is 0.79 eV (I–V) and 1.07 eV (C–V). It is observed that the barrier height increases to 0.85 eV (I–V) and 1.21 eV (C–V) after annealing at 300 °C for 1 min in N2 ambient. However, it is found that the SBH slightly decreases when the contacts are annealed at 400 and 500 °C and the corresponding values are 0.84 eV (I–V), 1.17 eV (C–V) for 400 °C and 0.80 eV (I–V), 1.11 eV (C–V) for 500 °C, respectively. Using Cheung's functions, the barrier height (Φb), ideality factor (n), and series resistance (Rs) are also calculated. From the above results, it is clear that the optimum annealing temperature for Ir Schottky contact is 300 °C. SIMS and XRD results shows that the formation of gallide phases at Ir/n‐InGaN interfaces could be the reason for variation in the SBHs upon annealing at elevated temperatures. Atomic force microscopy (AFM) results show that the overall surface morphology of Ir Schottky contacts on n‐InGaN stays reasonably smooth. These results make Ir Schottky contacts attractive for high‐temperature device applications.

Analysis of electronic parameters of nanostructure copper doped cadmium oxide/p-silicon heterojunction

The nanostructure Cu-doped CdO thin film was grown on p-type silicon substrate by sol–gel method. An Al/Cu doped CdO/p-Si heterojunction diode was fabricated. The values of ideality factor and barrier height for the Al/n-type CdO/p-Si heterojunction were obtained as 5.99 and 0.69eV, respectively. A modified Norde function combined with conventional forward I–V method was used to extract the junction parameters including the ideality factor, barrier height and series resistance. Norde function was compared with the Cheung functions and it is seen that there is a good agreement with both method for the series resistance values. Furthermore, the interface state density (NSS) as a function of energy distribution (ESS−EV) was extracted from the forward-bias I–V measurements by taking into account the bias dependence of the effective barrier height and series resistance.

The temperature dependent analysis of Au/TiO2 (rutile)/n-Si (MIS) SBDs using current–voltage–temperature (I–V–T) characteristics

In this study, the main electrical parameters of Au/TiO2(rutile)/n-Si Schottky barrier diodes (SBDs) were analyzed by using current–voltage–temperature (I–V–T) characteristics in the temperature range 200–380K. Titanium dioxide (TiO2) thin film was deposited on a polycrystalline n-type Silicon (Si) substrate using the DC magnetron sputtering system at 200°C. In order to improve the crystal quality deposited film was annealed at 900°C in air atmosphere for phase transition from amorphous to rutile phase. The barrier height (Φb) and ideality factor (n) were calculated from I–V characteristics. An increase in the value of Φb and a decrease in n with increasing temperature were observed. The values of Φb and n for Au/TiO2(rutile)/n-Si SBDs ranged from 0.57eV and 3.50 (at 200K) to 0.82eV and 1.90 (at 380K), respectively. In addition, series resistance (Rs) and Φb values of MIS SBDs were determined by using Cheung's and Norde's functions. Cheung's plots are obtained from the donward concave curvature region in the forward bias semi-logarithmic I–V curves originated from series resistance. Norde's function is easily used to obtain series resistance as a function of temperature due to current counduction mechanism which is dominated by thermionic emission (TE). The obtained results have been compared with each other and experimental results show that Rs values exhibit an unusual behavior that it increases with increasing temperature.

Effect of annealing temperature on electrical properties of Au/polyvinyl alcohol/n-InP Schottky barrier structure

In the present work, thin film of polyvinyl alcohol (PVA) is fabricated on n-type InP substrate as an interfacial layer for electronic modification of Au/n-InP Schottky contact. The electrical characteristics of Au/PVA/n-InP Schottky diode are determined at annealing temperature in the range of 100–300°C by current–voltage (I-V) and capacitance–voltage (C-V) methods. The Schottky barrier height and ideality factor (n) values of the as-deposited Au/PVA/n-InP diode are obtained at room temperature as 0.66eV (I-V), 0.82eV (C-V) and 1.32, respectively. Upon annealing at 200°C in nitrogen atmosphere for 1min, the barrier height value increases to 0.81eV (I-V), 0.99eV (C-V) and ideality factor decreases to 1.18. When the contact is annealed at 300°C, the barrier height value decreases to 0.77eV (I-V), 0.96eV (C-V) and ideality factor increases to 1.22. It is observed that the interfacial layer of PVA increases the barrier height by the influence of the space charge region of the Au/n-InP Schottky junction. The discrepancy between Schottky barrier heights calculated from I-V and C-V measurements is also explained. Further, Cheung's functions are used to extract the series resistance of Au/PVA/n-InP Schottky diode. The interface state density as determined by Terman's method is found to be 1.04×1012 and 0.59×1012cm−2eV−1 for the as-deposited and 200°C annealed Au/PVA/n-InP Schottky diodes. Finally, it is seen that the Schottky diode parameters changed with increase in the annealing temperature.

Analysis of the electrical characteristics of the Ag/ZnO Schottky barrier diodes on F-doped SnO2 glass substrates by pulsed laser deposition

High quality semiconductor layer of n-type ZnO thin film was fabricated on F-doped SnO2 glass substrates by pulsed laser deposition. The Schottky junction diodes with configuration of Ag/ZnO/FTO have been fabricated to study the devices electrical properties by current-voltage (I-V) and capacitance-voltage (C-V) measurements. The results show that the devices have good rectifying behaviors with an ideality factor of 1.64 and a Schottky barrier height of 0.85eV based on the I-V characteristics. Also, Cheung's functions and Norde's method were used to evaluate the I-V characteristics and to obtain the series resistance of the Schottky contact. From the C-V characteristics, the capacitance was determined to increase with decrease of frequencies. C-V measurements have resulted in higher barrier heights than those obtained from I-V measurements. The discrepancy between Schottky barrier heights obtained from I-V and C-V measurements was also interpreted.

The effects of 12 MeV electron irradiation on the electrical characteristics of the Au/Aniline blue/p-Si/Al device

An Au/Aniline blue (AB)/p-Si/Al structure has been fabricated and then the effect of electron irradiation (12 MeV electron energy and 5 × 10 12 e − cm −2 fluence) on the contact parameters of the device has been analysed by using the current–voltage ( I– V), capacitance–voltage ( C– V), and conductance–voltage ( G/ w– V) measurements, at room temperature. Since the organic layer creates a physical barrier between the metal and the semiconductor, it has been seen that the AB layer causes an increase in the effective barrier height of the device. Cheung functions, Norde model and conductance method have been used in order to determine the diode parameters. The values of the ideality factor, barrier height and series resistance increased after the electron irradiation. This has been attributed to a decrease in the net ionized dopant concentration that occurred as a result of electron irradiation.

Effects of temperature on series resistance determination of electrodeposited Cr/ n-Si/Au–Sb Schottky structures

Temperature dependences of the series resistance in the Cr/ n-Si/Au–Sb Schottky structures prepared by electrodeposition method have been studied using current–voltage ( I–V) characteristics in the 80–320 K temperature range by steps of 20 K. However, the values of series resistance obtained from Cheung functions were compared with each other, and it was seen that there is a good agreement between the values of the series resistance. A modified Norde’s function combined with conventional forward I–V method was used to extract the parameters including barrier height and the series resistance. The barrier height and series resistance obtained from Norde’s function were compared with those from Cheung functions. The values of barrier height and series resistance have very different especially towards to the lower temperatures. This is attributed to non-ideal I–V characteristics of the Cr/ n-Si/Au–Sb Schottky structure and non-pure thermionic emission theory due to the low temperature effects.

I– V characteristics of vanadium-flavonoid complexes based Schottky diodes

In this study, we have investigated the current–voltage characteristics of the Schottky diodes of two vanadium complexes, VO 2(3-fl) ( 1) (3-fl=3-hydroxyflavone) and VO(acac) 2 ( 2), (acac=acetylacetonate), and their composites with TiO 2. Thin films of vanadium complexes and their composites were deposited by the centrifugation method. Current–voltage characteristics of the samples were processed by the modified Shockley equation, Cheung functions and space-charge limited currents (SCLC) approaches. Different junction parameters, such as series resistances, reverse saturation currents, ideality factors and barrier height of the samples, were determined.