Barrier characteristics of Pt/Ru Schottky contacts on <Emphasis Type="Italic">n</Emphasis>-type GaN based on <Emphasis Type="Italic">I–V–T</Emphasis> and <Emphasis Type="Italic">C–V–T</Emphasis> measurements

We have investigated the current–voltage (I–V) and capacitance–voltage (C–V) characteristics of Ru/Pt/n-GaN Schottky diodes in the temperature range 100–420 K. The calculated values of barrier height and ideality factor for the Ru/Pt/n-GaN Schottky diode are 0·73 eV and 1·4 at 420 K, 0·18 eV and 4·2 at 100 K, respectively. The zero-bias barrier height (Φ_b0) calculated from I–V characteristics is found to be increased and the ideality factor (n) decreased with increasing temperature. Such a behaviour of Φ_b0 and n is attributed to Schottky barrier (SB) inhomogeneities by assuming a Gaussian distribution (GD) of barrier heights (BHs) at the metal/semiconductor interface. The current–voltage–temperature (I–V–T) characteristics of the Ru/Pt/n-GaN Schottky diode have shown a double Gaussian distribution having mean barrier heights ( [`(F)]<sub>\textb0</sub> {\bar{{\Phi}}_{\text{b}0}} ) of 1·001 eV and 0·4701 eV and standard deviations (σ <sub>0</sub>) of 0·1491 V and 0·0708 V, respectively. The modified ln (J<sub>0</sub> /T<sup>2</sup> )-( q<sup>2</sup>s <sub>0</sub><sup>2</sup>/2k<sup>2</sup>T<sup>2</sup> ){ln} ({{J}_{0} /{T}^{2}} )-( {{q}^{2}{\sigma} _{0}^{2}/{2}{k}^{2}{T}^{2}} ) vs 10<sup>3</sup>/T plot gives [`(F)]_\textb0 \bar{{\Phi}}_{\text{b}0} and Richardson constant values as 0·99 eV and 0·47 eV, and 27·83 and 10·29 A/cm²K², respectively without using the temperature coefficient of the barrier height. The difference between the apparent barrier heights (BHs) evaluated from the I–V and C–V methods has been attributed to the existence of Schottky barrier height inhomogeneities.     

Electrical and structural properties of double metal structure Ni/V Schottky contacts on n-InP after rapid thermal process

The electrical, structural, and surface morphological properties of Ni/V Schottky contacts have been investigated as a function of annealing. The Schottky barrier height value from I–V and C–V measurements for as-deposited Ni/V/n-InP diode is 0.61 eV (I–V) and 0.91 eV (C–V), respectively. It has been observed that the Schottky barrier height decreases with increasing annealing temperature as compared to the as-deposited contact. For the contact annealed at 200 °C, the obtained barrier height decreased to 0.52 eV (I–V) and 0.78 eV (C–V). Further, the annealing temperature increased to 300 and 400 °C, the barrier height slightly increased to 0.58 eV (I–V), 0.82 eV (C–V) and 0.59 eV (I–V), 0.88 eV (C–V). However, after annealing at 500 °C, results then decrease in barrier height to 0.51 eV (I–V) and 0.76 eV (C–V), which is lower than the value obtained for the sample annealed at 200 °C. The Norde method is also employed to extract the barrier height of Ni/V/InP Schottky diode, and the values are 0.68 eV for the as-deposited and 0.56 eV for the contact annealed at 500 °C, which are in good agreement with those obtained by I–V technique. Based on the results of AES and XRD studies, it is concluded that the formation of indium phases at the Ni/V/n-InP interface may be the reason for the increase in the barrier height for the as-deposited contact. The decrease in the barrier height upon annealing at 500 °C may be due to the formation of phosphide phases at the interface. The AFM results showed that there is no significant degradation in the surface morphology (RMS roughness of 0.61 nm) of the contact even after annealing at 500 °C.     

Temperature-dependent current–voltage and capacitance–voltage characteristics of the Ag/n-InP/In Schottky diodes

The current–voltage (I–V) and capacitance–voltage (C–V) characteristics of Ag/n-InP/In Schottky diodes have been studied in a wide temperature range by steps of 10 K. A decrease in the apparent barrier height (BH), , an increase in the ideality factor, and a nonlinearity in the activation energy plot with a decrease in temperature have been seen. The experimental values of BH and ideality factor for the devices were calculated as 0.61 eV and 1.18 at 320 K, 0.48 eV and 1.52 at 200 K, and 0.20 eV and 3.89 at 70 K, respectively. An abnormal decrease in the experimental BH and an increase in the ideality factor n with a decrease in temperature have been explained by the barrier inhomogeneities at the metal–semiconductor (MS) interface. From the temperature dependent I–V characteristics of the Ag/n-InP contact, that is, and A* as 0.79 and 0.55 eV, and 7.96 and , respectively, have been calculated from a modified vs. 1/T plot for the two temperature regions. The Richardson constant values are in close agreement with the value of known for n-type InP. Moreover, the difference between the apparent BHs obtained from the I–V and C–V characteristics has been attributed to the existence of Schottky BH inhomogeneity.     

The influence of rapid thermal annealing on electrical and structural properties of Pt/Au Schottky contacts to n-type InP

The electrical and structural properties of Pt/Au Schottky contacts to n-InP have been investigated in the annealing temperature range of 200–500 °C by current–voltage (I–V), capacitance–voltage (C–V), Auger electron spectroscopy (AES) and X-ray diffraction (XRD) measurements. The barrier height of as-deposited Pt/Au Schottky contact is found to be 0.46 eV (I–V) and 0.68 eV (C–V). For the contacts annealed at 300 °C, the barrier height is increased to 0.51 eV (I–V) 0.89 eV (C–V). Further increase in annealing temperature up to 500 °C, the barrier height has been found to decrease to 0.49 eV (I–V) 0.82 eV (C–V) from those values obtained at 300 °C. It has been found that the electrical characteristics are significantly improved for Pt/Au Schottky contacts upon annealing at 300 °C. Based on the Auger electron spectroscopy and X-ray diffraction results, the formation of Pt–In and Au–In intermetallic compounds at the interface may be the reason for the increase of barrier height after annealing at 300 °C for Pt/Au Schottky contacts. From the atomic force microscopy (AFM) results, it is evident that the surface becomes smooth with RMS roughness of 16.91 nm for the Pt/Au Schottky contacts after annealing at 500 °C compared to the 300 °C annealed sample (RMS roughness of 17.33 nm).     

Current-voltage and capacitance-voltage characteristics of polypyrrole/p-InP structure

The polypyrrole/p-InP structure has been made by the electrochemical polymerization of the organic polypyrrole onto the p-InP substrate. The current-voltage (I-V) and capacitance-voltage (C-V) characteristics of diode have been determined at room temperature and different frequencies. At each frequency, the measured capacitance decreases with increasing frequency due to a continuous distribution of the interface states in the frequency range 50 kHz-1 MHz. From the I-V characteristics of the polypyrrole/p-InP structure, ideality factor and barrier height (BH) values of 1.68 and 0.59 eV, respectively, were obtained from a forward-bias I-V plot. The diode shows non-ideal I-V behavior with ideality greater than unity. This is attributed to the interfacial layer, the interface states and barrier inhomogeneity of the device. As expected, the C-V curves gave a BH value higher than those derived from I-V measurements. This discrepancy can be explained from the fact that due to the different nature of the C-V and I-V measurement techniques, BHs deduced from them are not always the same.     

Photoresponse of n -ZnO/ p -Si heterojunction towards ultraviolet/visible lights: thickness dependent behavior

A series of n-ZnO/p-Si thin film heterojunctions have been fabricated by a low cost sol–gel technique for different ZnO film thicknesses and the dark as well as photo current–voltage (I–V) characteristics have been investigated in details. The heterojunction with ZnO thickness of 0.46 μm shows the best diode characteristics in terms of rectification ratio, I _F/I _R = 5.7 × 10³ at 5 V and reverse leakage current density, J _R = 7.6 × 10⁻⁵ A cm⁻² at −5 V. From the photo I–V curves and wavelength dependent photocurrent of the heterojunctions, it is found that the junction with 0.46 μm ZnO thickness shows the highest sensitivity towards both UV and visible lights.     

Temperature-dependent barrier height in CdSe Schottky diode

This article reports the measurements of temperature-dependent barrier height (BH) of CdSe Schottky diodes. These diodes have been made by thermal evaporation technique on ITO glass and glass substrates at room temperature. The XRD measurements have been made and the average particle size has been calculated which comes out to be ~20 nm. The Au dots have been made for non-ohmic contacts. I–V characteristics have been measured at different temperatures (280–330 K). These characteristics obey the thermionic emission theory. The BH decreases and ideality factor increases with the increase in temperature. Richardson’s plot has been made and Richardson’s constant has been calculated which is less than the expected value. Capacitance measurements have been done at different frequencies and the interface states have been calculated. The results have been explained on the basis of BH inhomogeneities.     

Effect of annealing temperature on electrical characteristics of ruthenium-based Schottky contacts on n-type GaN

The electrical properties of ruthenium (Ru) and ruthenium/gold (Ru/Au) Schottky contacts on n-type GaN are investigated as a function of annealing temperature by current–voltage (I–V) and capacitance–voltage (C–V) techniques. The Schottky barrier height of as-deposited Ru/n-GaN is found to be 0.88 eV (I–V) and 1.10 eV (C–V) respectively. However, after annealing at 500°C for 1 min in the nitrogen ambient, the decrease in barrier height is quite considerable and found to be 0.80 eV (I–V) and 0.86 eV (C–V). In the case of Ru/Au Schottky diode the measured barrier height is 0.75 eV (I–V) and 0.93 eV (C–V). In contrast to the Ru contacts, it is interesting to note that the barrier height of Ru/Au depends on the annealing temperature. Annealing at 300°C improves the barrier height and the corresponding values are 0.99 and 1.34 eV. Further increase in annealing temperature decreases the barrier height and the respective values are 0.72 and 1.08 eV at 500°C. From the above observations, it is clear that the electrical properties of annealed Ru/Au contacts are improved compared to the as-deposited films. However, Ru Schottky contacts exhibit a kind of thermal stability during annealing.     

Effect of an organic compound (Methyl Red) interfacial layer on the calculation of characteristic parameters of an Al/Methyl Red/p-Si sandwich Schottky barrier diode

An Al/Methyl Red/p-Si sandwich Schottky barrier diode (SBD) has been fabricated by adding a solution of the organic compound Methyl Red in chloroform onto a p-Si substrate, and then evaporating the solvent. Current-voltage (I-V) measurements of the Al/Methyl Red/p-Si sandwich SBD have been carried out at room temperature and in the dark. The Al/Methyl Red/p-Si sandwich SBD demonstrated rectifying behavior. Barrier height (BH) and ideality factor values of 0.855 eV and 1.19, respectively, for this device have been determined from the forward-bias I-V characteristics. The Al/Methyl Red/p-Si sandwich SBD showed non-ideal I-V behavior with the value of ideality factor greater than unity. The energy distribution of the interface state density determined from I-V characteristics increases exponentially with bias from 3.68 × 10¹² cm^− 2 eV^− 1 at (0.81 − E_v) eV to 9.99 × 10¹³ cm^− 2 eV^− 1 at (0.69 − E_v) eV.     

The analysis of the current–voltage characteristics of the high barrier Au/Anthracene/n-Si MIS devices at low temperatures

The Au/Anthracene/n-Si/Al MIS device was fabricated on the basis of anthracene film covalently bonded to a Si substrate. The MIS device showed Schottky behavior with barrier heights of 0.85 eV and ideality factors of 1.88 at 300 K. The barrier height of the Au/n-Si has increased after deposition of the anthracene layer onto Si. Temperature dependent current–voltage (I–V) measurements were performed on the Au/Anthracene/n-Si/Al MIS diodes in the range 140–300 K. From the temperature dependence of forward bias I–V, the barrier height was observed to increase with temperature. However, the ideality factor decreased with increasing temperature. The values of activation energy (E_a) and Richardson constant (A*) were determined as 0.24 eV and 7.57 × 10⁻⁶ A cm⁻² K⁻² from the slope and the intercept at ordinate of the linear region of Richardson plot, respectively. The increase of the series resistance R_s with the fall of temperature was attributed to lack of free carrier concentration at low temperatures.     

Electrodeposited heterojunctions based on cadmium chalcogenide, CdX (X = S, Se, Te) and polyaniline

We have fabricated heterojunctions based on all-electrodeposited cadmium chalcogenides CdX (X = S, Se, Te) and polyaniline thin film. Cadmium chalcogenide films were deposited onto low cost stainless steel substrate using potentiostatic mode. Over Cd chalcogenide film, polyaniline was deposited potentiodynamically. The junctions were heated at 353 K for 20 min and junction current–voltge (I–V) and capacitance–voltage (C–V) plots were studied. From I–V plots, junction ideality factors for heterojunction based on CdS, CdSe and CdTe were calculated to be 1.55, 1.60 and 1.89, respectively. Studies on C-V plots revealed flat band potentials for heterojunction based on CdS, CdSe and CdTe to be + 0.4, + 0.45, and + 0.64 V, respectively.     

Photoelectrochemical applications of In<Subscript>2</Subscript>Se<Subscript>3</Subscript> thin films by chemical deposition

Indium selenide films have been synthesized by chemical bath deposition method onto stainless steel plate. The configuration of fabricated cell is n-In₂Se₃| NaOH(1 M) + S(1 M) + Na₂S(1 M) |C_(graphite). Characterization of the photoelectrochemical cell was carried out by studying X-ray diffraction, current–voltage and capacitance–voltage characteristics in the dark, barrier height measurements, power output, photoresponse and spectral response. The study shows that the In₂Se₃ thin films are n-type semiconductor. The junction ideality factor was found to be 3.24. The flat band potential and the barrier height were found to be 0.720 V and 0.196 eV, respectively. From the study of power output characteristics, open circuit voltage, short circuit current, fill factor and efficiency were found to be 310 mV, 20 μA, 37.64 and 0.61%, respectively. Photoresponse studies show that the lighted ideality factor is 2.78. Maximum current was observed at 575 nm.     

Investigation of current injection in β-FeSi2/Si double-heterostructures light-emitting diodes by molecular beam epitaxy

The p-Si/p-β-FeSi₂/p-Si/n-Si light-emitting diode (LED) was fabricated by molecular beam epitaxy (MBE) on Si(111) substrates. Compared to our previous p-Si/p-β-FeSi₂/n-Si double heterostructures (DH) LED, the turn-on voltage in the current-voltage (I-V) characteristics increased by approximately 0.2 V, meaning that defect densities at around the p-n junction were reduced. However, Si-related EL (1.05 eV) became dominant unexpectedly, and thus EL of β-FeSi₂ was suppressed accordingly. The origin of the luminescence is considered to be transitions via defect levels (1.05 eV) being due probably to Fe-B complex.     

Properties of PEDOT:PEG/ZnO/p-Si heterojunction diode

The zinc oxide (ZnO) and poly(3,4-ethylenedioxythiophene) bis-poly(ethyleneglycol) (PEDOT:PEG) films were deposited on p-Si substrate by sputter and spin coating methods, respectively. An organic/inorganic heterojunction diode having PEDOT:PEG/ZnO on p-Si substrate was fabricated. The barrier height (BH) and the ideality factor values for the device were found to be 0.82 ± 0.01 eV and 1.9 ± 0.01, respectively. It has been seen that the value of BH is significantly larger than those of conventional Au/p-Si metal–semiconductor contacts. The PEDOT:PEG/ZnO/p-Si heterostructure exhibits a non-ideal I–V behavior with the ideality factor greater than unity that could be ascribed to the interfacial layer, interface states and series resistance. The modified Norde's function combined with conventional forward I–V method was used to extract the parameters including the barrier height and series resistance. At the same time, the physical properties of ZnO and PEDOT:PEG films deposited by sputter and spin coating technique, respectively, were investigated at room temperature. The obtained results indicate that the electrical parameters of the diode are affected by structural properties of ZnO film and PEDOT:PEG organic film.     

Effects of illumination on electrical parameters of Ag/n-CdO/p-Si diode

The current–voltage (I–V) characteristics of the Ag/n-CdO/p-Si diode were investigated under various white light (visible light) illuminations. The electrical parameters such as ideality factor (n), zero-bias-barrier height (Φ_b) and series resistance (R_S) of Ag/n-CdO/p-Si MIS diodes were determined by using the forward bias current–voltage measurements. The Ag/n-CdO/p-Si diode exhibits a non-ideal behavior due to the interfacial layer, the interface states and the series resistance. The ideality factor is increased, while the barrier height is decreased with decreasing illumination intensities. The values of R_S obtained from Cheung and Norde methods are decreased with increasing illumination intensity. The distribution profile of the interface states (N_SS) as a function of energy distribution (E_SS − E_V) was extracted from the forward I–V measurements under various illumination intensities. The interface state densities were observed to be strongly illumination dependent and are decreased with increasing illumination intensities.     

Influence of tetramethylammonium hydroxide treatment on the electrical characteristics of Ni/Au/GaN Schottky barrier diode

The effect of tetramethylammonium hydroxide (TMAH) treatment on the electrical properties of Ni/Au/GaN Schottky diodes have been investigated by current–voltage (I–V) and capacitance–voltage (C–V) techniques. The barrier heights and ideality factors measured from I–V characteristics are found to be 0.70 eV and 1.32 for without TMAH treatment, and 0.78 eV and 1.14 for with TMAH treatment, respectively. Cheung method is used to measure the series resistance and barrier height of the Schottky diodes, and the barrier height consistency is checked using the Norde method. The magnitude of interface state density for the diodes without and with TMAH treatment are varied from 7.45 × 10¹³ eV⁻¹ cm⁻² to 6.09 × 10¹² eV⁻¹ cm⁻² and 4.03 × 10¹³ eV⁻¹ cm⁻² to 1.79 × 10¹² eV⁻¹ cm⁻² in the below the conduction band from E_C-0.19 eV to E_C-0.63 eV and E_C-0.22 eV to E_C-0.73 eV. Based on the results, the TMAH treatment effectively removes of surface oxide (Ga_xO_y) layer, formed due to the incorporation of the residual oxygen with Ga atom at the GaN surface during the plasma etching. The decrease in interface state density at the Ni/Au/GaN interface could be the reason for the improvement in the electrical properties.     

Electrical and optical properties of poly(2-dodecanoylsulfanyl-<Emphasis Type="Italic">p</Emphasis>-phenylenevnylene) and its application in electroluminescent devices

We describe the optical and electrical characterization of a poly(p-phenylenevinylene) derivative: poly(2-dodecanoylsulfanyl-p-phenylenevinylene) (12COS-PPV). The electrical characterization was carried out on devices with the FTO\PEDOT:PSS\12COS-PPV/Al structure. Positive charge carrier mobility μ _h of ~1.0 × 10⁻⁶ cm² V⁻¹ s⁻¹ and barrier height φ of ~0.1 eV for positive charge carrier injection at the PEDOT:PSS/12COS-PPV interface were obtained using a thermionic injection model. FTO\PEDOT:PSS\12COS-PPV/Ca devices exhibited green-yellow electroluminescence with maximum emission at λ = 540 nm.     

Anomalous Change of Transport Characteristics of Graphite Planar-Type Micro-structures Fabricated by Focused Ion Beam

We report the observation of an anomalous change of transport characteristics of planar-type microstructures (along ab-plane and c-axis) fabricated on thin graphite layer using a three-dimensional focused-ion-beam (FIB) etching technique. We have fabricated several in-plane area of sizes of 6 μm × 6 μm, 6 μm × 4 μm and 6 μm × 2 μm planar-type microstructures/patterns on thin graphite layer using FIB. The c-axis stack with the height of several nanometers was also fabricated. The transport characteristics were studied for these structures. We have observed a peculiar anomalous transition from ohmic behavior to curve-like nonlinear characteristics below 110 K from current (I)–voltage (V) curves for ab-plane and c-axis stack. Clear nonlinear characteristics have been observed at 25 K. Resistance versus temperature (R–T) and I–V characteristics of the ab-plane and c-axis stack strongly resemble this anomalous-transition behavior. These results show the superiority of graphite-microstructures for future graphite-based nonlinear electronic devices.     

Density of states effective mass of SnBi<Subscript>4</Subscript>Se<Subscript>7</Subscript> deduced from the temperature dependence of electrical conductivity in the activation regime

Current–voltage (I–V) measurements on polycrystalline samples of Bi₂Se₃ and stoichiometric ternary compound in the quasi-binary system of SnSe–Bi₂Se₃ at different temperatures in the vicinity of room temperature have been performed. Also, temperature dependence of electrical conductivity has been measured. From the analysis of the temperature dependence of electron concentration in the activation regime above room temperature, the density of states effective mass, m*, has been determined. Some intrinsic and contact properties such as barrier heights, ideality factors, and carriers concentrations have been investigated using I–V characteristics. It has been found that all samples exhibit ohmic and space charge limited conduction at low and high fields, respectively.     

NOA61 photopolymer as an interface for Al/NOA61/p-Si/Al heterojunction MPS device

The effect of the NOA61 photopolymer organic interlayer on the electrical and dielectric properties of the Al/NOA61/p-Si/Al metal-polymer-semiconductor (MPS) device has been reported the first time. The device parameters of the device such as rectification ratio (RR), ideality factor (n), and barrier height (Φ_B) were determined from the current–voltage (I–V) measurements according to thermionic emission theory (TE). Series resistance, R_S, values were also calculated by Norde and Cheung methods in the range of 2.4–3 kΩ. According to the reverse bias I–V measurements, the current was governed by Frenkel–Poole Emission (FPE) in the entire region. The voltage-dependent capacitance (C) and the conductance (G/ω) measurements were investigated at particular frequencies between 20 kHz and 1 MHz. The dielectric constant (ε′), dielectric loss (ε″), loss tangent (tanδ), and the complex electric modulus (M) were calculated using the measured C and G parameters, and it was seen that the interface states and surface dipoles at the interfacial layer were effective in the behavior of the device in alternating current. Additionally, the morphological properties of the thin film were studied by scanning electron microscopy (SEM). We observed that (NOA61) organic interlayer may be a noticeable alternative to a variety of electronic applications.