Electrical characteristics of Pd Schottky contacts on ZnO films

The electrical characteristics of Pd Schottky contacts on ZnO films have been investigated by current-voltage (I–V) and capacitance–voltage (C–V) measurements at different temperatures. ZnO films of two thicknesses (400 nm and 1000 nm) were grown by DC-magnetron sputtering on n-Si substrates. The basic structural, optical and electrical properties of these films are also reported. We compared the two Schottky diodes by means of characteristic parameters, such as rectification ratio, ideality factor (η), barrier height (Φ_b) and series resistance and obtained better results for the 1000 nm-ZnO Schottky diodes. We also discussed the dependence of I‐V characteristics on temperature and the two distinct linear regions observed at low temperatures are attributed to the existence of two different inhomogeneous barrier heights. From I–V plots in a log-log scale we found that the dominant current-transport mechanism at large forward bias is space-charge limited current (SCLC) controlled by the presence of traps within the ZnO bandgap. The existence of such traps (deep states or interface states) is demonstrated by frequency-dependent capacitance and deep-level transient spectroscopy (DLTS) measurements.     

Effect of annealing atmosphere on the electrical properties of nickel oxide/zinc oxide p–n junction grown by sol–gel technique

Zinc oxide (ZnO) and nickel oxide (NiO) thin films were prepared on glass substrates by a sol–gel method. Spin coating was used to fabricate a p-NiO/n-ZnO junction. The influence of the post annealing atmosphere (air or nitrogen) on the microstructure and surface morphology of NiO and ZnO thin films and the p-NiO/n-ZnO junction are examined. The structural properties are characterized by X-ray diffraction (XRD) and the surface morphology of the thin films and the p–n junction are investigated by atomic force microscopy (AFM). Optical properties are investigated by UV–visible spectroscopy and the electrical properties, such as I–V photocurrent, are characterized by a voltage source meter instrument. XRD patterns show that the films are polycrystalline with preferred orientation in the (002) direction for the ZnO films and the (200) direction for the NiO films. The AFM results indicate that the morphology of the ZnO and NiO films and the p-NiO/n-ZnO junction are mainly influenced by the annealing atmosphere. All films have a high optical transmittance of about 80% in the visible region and a sharp absorption edge. The optical band gaps of the two materials change with the annealing atmosphere (air or nitrogen). The p-NiO/n-ZnO heterojunction device has an average transmittance of over 80% in the visible region, which lies between the transmittance of the ZnO and NiO films separately. The ideality factor, barrier height, and series resistance of the heterojunction treated in different annealing atmospheres are determined by using conventional forward bias I–V characteristics and also Norde׳s and Cheung׳s methods.     

The effects of thermal annealing on the electrical characteristics of Au/n–InP/In diode

An Au/n–InP/In diode has been fabricated in the laboratory conditions and the current–voltage (I–V) and capacitance–voltage (C–V) characteristics of the diode have been measured in room temperature. In order to observe the effect of the thermal annealing, this diode has been annealed at temperatures 100 and 200 °C for 3 min in N₂ atmosphere. The characteristic parameters such as leakage current, barrier height and ideality factor of this diode have been calculated from the forward bias I–V and reverse bias C–V characteristics as a function of annealing temperature. Also the rectifying ratio of the diode is evaluated for as-deposited and annealed diode.     

Study of the I–V characteristics of nanostructured Pd films on a Si substrate after vacuum annealing

The I–V characteristics of nanostructured Pd films on a Si substrate are investigated. The nanostructures (nanoislands) are formed by the vacuum annealing of continuous ultrathin Pd films sputtered onto a substrate. The shape of the I–V characteristics of the investigated Si substrate-Pd film system is shown to be heavily dependent on the degree of film nanostructuring. The surface morphology of the films is studied using scanning electron microscopy.     

Effect of annealing in argon on the properties of thermally deposited gallium-oxide films

The effect of the annealing temperature on the I–V, C–I, and G–V characteristics and transparency of gallium-oxide films is investigated. The films are fabricated by the thermal evaporation of Ga₂O₃ powder on n-GaAs wafers. It is shown that the films which are amorphous after deposition crystallize upon annealing at temperatures T _an ≥ 800°C. The electrical characteristics and photoresponse of the V/Ni-GaAs-GaAs-Ga _x O _y -V/Ni samples to visible radiation depend on the structure and phase composition of the films.     

Interface States of Fe3O4/Si Interfacial Structure and Effect of Magnetic Field

Electronic transport across Fe₃O₄/Si interfacial structure has been studied with and without the application of magnetic fields along the interfacial plane, up to 8 kG. Current–voltage (I–V) and capacitance–voltage (C–V) characteristics across the junction have been recorded for various bias voltages, frequency and magnetic field. The interfacial parameters, such as, ideality factor (n), barrier height (? _B0), series resistance (R _S) and donor concentration (N _D) etc. have been estimated from the characteristics. The interface state density (N _SS) and their energy distribution have been estimated by using the interfacial parameters. It has been observed that the N _SS decreases as the energy increases from the conduction band edge towards the valence band. A magnetoresistance (MR) of ～40% has been estimated from the I–V–H data along with its variation with magnetic field. The change of interface state density with the magnetic field shows a similar variation as MR versus H. From the observed variations, the interface states seem to be related to electronic spins. The possibility of an interfacial magnetic silicide or magnetic ions in the interfacial region has been invoked for the observed interface states.     

Effect of hydrogen on interface of metal–semiconductor Schottky diode

The effect of hydrogen on p-type Si/Mn and Si/Co Schottky diode has been investigated in present studies. The variations of I–V characteristics suggested that the rectifying act of these diodes change with variation of hydrogen pressure, which is due to the diffusion of hydrogen through the Mn and Co metal films up to Si surface or a creation of surface states at the interface. It is also observed that the effect of hydrogen found to be reverse in order for forward as well as reverse direction of current in Mn and Co deposited films on Si substrate, corresponding to anionic and protonic model of hydrogen interaction with metals. One can say that hydrogen plays an amphoteric role to neutralize either donors or acceptors level in semiconductors and metals. The Raman spectra of Si/Mn and Si/Co are taken and stoke lines link with the presence of hydrogen is observed. In this paper, we are presenting the role of hydrogen pressure on I–V characteristics at the interface of metal–semiconductor structure.     

Calculation from the current-voltage and capacitance-voltage measurements of characteristics parameters of Cd/CdS/n-Si/Au-Sb structure with CdS interface layer grown on n-Si substrate by SILAR method

The CdS thin film has been directly formed on n-type Si substrate to form an interfacial layer between cadmium (Cd) and n-type Si with Successive Ionic Layer Adsorption and Reaction (SILAR) method. An Au-Sb electrode has been used as an ohmic contact. The Cd/CdS/n-Si/Au-Sb structure has demonstrated clearly rectifying behaviour by the current-voltage (I-V) curves studied at room temperature. The characteristics parameters such as barrier height, ideality factor and series resistance of Cd/CdS/n-Si/Au-Sb structure have been calculated from the forward bias I-V and reverse bias C⁻²-V characteristics. The diode ideality factor and the barrier height have been calculated as n = 2.06 and Φ_b = 0.92 eV by applying a thermionic emission theory, respectively. The diode shows non-ideal I-V behaviour with an ideality factor greater than unity that can be ascribed to the interfacial layer, the interface states and the series resistance. At high current densities in the forward direction, the series resistance (R_s) effect has been observed. The values of R_s obtained from dV/d(lnI)-I and H(I)-I plots are near to each others (R_s = 182.24 Ω and R_s = 186.04 Ω, respectively). This case shows the consistency of the Cheung′s approach. In the same way, the barrier height calculated from C⁻² -V characteristics varied from 0.698 to 0.743 eV. Furthermore, the density distribution of interface states (N_ss) of the device has been obtained from the forward bias I-V characteristics. It has been seen that, the N_ss has almost an exponential rise with bias from the mid gap toward the bottom of conduction band.     

A novel hetero-junction Tunnel-FET using Semiconducting silicide–Silicon contact and its scalability

A new type of silicon-based Tunneling FET (TFET) using semiconducting silicide Mg₂Si/Si hetero-junction as source-channel structure is proposed and the device simulation has been presented. With narrow bandgap of silicide and the conduction and valence band discontinuous at the hetero-junction, larger drain current and smaller subthreshold swing than those of Si homo-junction TFET can be obtained. Structural optimization study reveals that low Si channel impurity concentration and the alignment of the gate electrode edge to the hetero-junction lead to better performance of the TFET. Scaling of the gate length increases the off-state leakage current, however, the drain voltage (V_d) reduction in accordance with the gate scaling suppresses the phenomenon, keeping its high drivability.     

Electrical property dependence on thickness and morphology of nanocrystalline diamond thin films

In this study, we investigate the influence of nanocrystalline diamond (NCD) thin film morphology and thickness on their electrical properties. NCD films are grown on p-type Si substrates with varied thicknesses from 250 to 788 nm. Electrical contacts are formed from combination of Ti/Au metal layers (100 nm thick each). The I-V and breakdown field measurements are used to analyze the electrical properties of metal/NCD/Si sandwich structure. In addition, NCD films are analyzed by scanning electron microscopy and Raman spectroscopy for better interpretation of the I-V measurements.     

Evaluation of the hydrostatic pressure effect on Mn/p-Si Schottky barrier diode electrical parameters and interface states

Mn/p-Si Schottky barrier diode (SBD) electrical parameters and interface state density have been investigated with current–voltage (I–V) characteristics and Cheung's functions employing hydrostatic pressure. The interface state density of the diodes has an exponential growth with bias from the midgap towards the top of the valance band. We have seen that the Schottky barrier height (SBH) for Mn/p-Si SBD has a pressure coefficient of 1.61 meV/kbar (16.1 meV/GPa). We have reported that the p-type barrier height exhibited a weak pressure dependence, accepting that the Fermi level at the interface do not shift as a function of the pressure.     

Fabrication and characteristics of MOS-FET's incorporating anodic aluminum oxide in the gate structure

Anodic aluminum oxide films have been grown by means of a simple process which is compatible with the existing planar silicon IC fabrication technology. Device structures have been fabricated and tested in order to demonstrate the usefulness of anodized layers of evaporated aluminum in a multiple layer metallization scheme. Results of anodization of thin aluminum layers on a silicon substrate indicate complete conversion of aluminum into aluminum oxide and in addition, formation of a thin underlying layer of silicon dioxide. For the anodic aluminum oxide a growth rate of 11·5 Å/volt at a current density of 0·5 mA/cm² has been found to produce quite satisfactory quality of insulting layers. Experimental results are presented illustrating the C?V and I?V characteristics of p-channel MOS-FET's with both the partially anodized stacked-gate structure and the over-anodized double-oxide layer gate structure.     

Deposition of HfO2 on InAs by atomic-layer deposition

Metal–oxide–semiconductor (MOS) capacitors are formed on bulk InAs substrates by atomic-layer deposition (ALD) of HfO₂. Prior to film growth, InAs substrates receive a wet-chemical treatment of HCl, buffered HF (BHF), or (NH₄)₂S. Hafnium dioxide films are grown using 75 ALD cycles with substrate temperatures of 100, 200, and 300 °C. Substrate temperature is found to have a significant influence on the current–voltage (I–V) and capacitance–voltage (C–V) characteristics of the capacitors, while the influence of substrate pretreatment manifests itself in interface trap density, D_it, as measured by the Terman method.     

CdTe/CdS多晶薄膜太阳能电池正向电流的计算机模拟分析

应用数值方法来解CdTe／CdS异质结J－V特性，进而得出其二极管理想因子、激活能以及异质结空间电荷区党度。结果表明，CdTe一侧空间电荷区复合是主导CdTe／CdS异质结传输电流的主要机制。说明在CdTe基太阳能电池制造中，控制多晶薄膜化学缺陷对提高电池能量转换效率的重要意义。     

Structural and Electrical Properties of Ag/<Emphasis Type="Italic">n</Emphasis>-TiO<Subscript>2</Subscript>/<Emphasis Type="Italic">p</Emphasis>-Si/Al Heterostructure Fabricated by Pulsed Laser Deposition Technique

We have investigated the structural and electrical characteristics of the Ag/n-TiO₂/p-Si/Al heterostructure. Thin films of pure TiO₂ were deposited on p-type silicon (100) by optimized pulsed laser ablation with a KrF-excimer laser in an oxygen-controlled environment. X-ray diffraction analysis showed the formation of crystalline TiO₂ film having a tetragonal texture with a strong (210) plane as the preferred direction. High purity aluminium and silver metals were deposited to obtain ohmic contacts on p-Si and n-TiO₂, respectively. The current–voltage (I–V) characteristics of the fabricated heterostructure were studied by using thermionic emission diffusion mechanism over the temperature range of 80–300 K. Parameters such as barrier height and ideality factor were derived from the measured I–V data of the heterostructure. The detailed analysis of I–V measurements revealed good rectifying behavior in the inhomogeneous Ag/n-TiO₂/p-Si(100)/Al heterostructure. The variations of barrier height and ideality factor with temperature and the non-linearity of the activation energy plot confirmed that barrier heights at the interface follow Gaussian distributions. The value of Richardson’s constant was found to be 6.73 × 10⁵ Am^?2 K^?2, which is of the order of the theoretical value 3.2 × 10⁵ Am^?2 K^?2. The capacitance–voltage (C–V) measurements of the heterostructure were investigated as a function of temperature. The frequency dependence (Mott–Schottky plot) of the C–V characteristics was also studied. These measurements indicate the occurrence of a built-in barrier and impurity concentration in TiO₂ film. The optical studies were also performed using a UV–Vis spectrophotometer. The optical band gap energy of TiO₂ films was found to be 3.60 eV.     

Temperature dependent of the current–voltage (I–V) characteristics of TaSi2/n-Si structure

Tantalum silicide (TaSi₂) thin films were deposited on n-type silicon single crystal substrates using a dual electron-gun system and with Ta and Si targets. The electrical transport properties of the TaSi₂/n-Si structures were investigated by temperature-dependent current–voltage (I–V) measurements. The temperature-dependent I–V characteristics revealed that the forward conduction was determined by thermionic-emission and space-charge-limited current mechanisms at low and high voltage respectively. On the other hand, the reverse current is limited by the carrier generation process.     

Electrical characteristics and inhomogeneous barrier analysis of Au-Be/p-InSe:Cd Schottky barrier diodes

We have identically prepared Au-Be/p-InSe:Cd Schottky barrier diodes (SBDs) (21 dots) on the InSe:Cd substrate. The electrical analysis of Au-Be/p-InSe:Cd structure has been investigated by means of current-voltage (I-V), capacitance-voltage (C-V) and capacitance-frequency (C-f) measurements at 296 K temperature in dark conditions. The effective barrier heights and ideality factors of identically fabricated Au-Be/p-InSe:Cd SBDs have been calculated from their experimental forward bias current-voltage (I-V) characteristics by applying a thermionic emission theory. The BH values obtained from the I-V characteristics have varied between 0.74 eV and 0.82 eV with values of ideality factors ranging between 1.49 and 1.11 for the Au-Be/p-InSe:Cd SBDs. It has been determined a lateral homogeneous barrier height value of approximately 0.82 eV for these structures from the experimental linear relationship between barrier heights and ideality factors. The Schottky barrier height (SBH) value has been obtained from the reverse-bias C-V characteristics of Au-Be/p-InSe:Cd SBD for only one diode. At high currents in the forward direction, the series resistance effect has been observed. The value of series resistance has been determined from I-V measurements using Cheung’s and Norde’s methods.     

Structural,optical and electrical properties of MgxZn1−xO ternary alloy films

The structural, optical and electrical properties of Mg_xZn_1−xO (x=0.05–0.3) ternary alloy thin films deposited by the sol–gel method on the glass substrate were investigated. The presence of Mg in deposited samples was confirmed through EDAX. XRD spectra revealed that the deposited Mg doped ZnO films were polycrystalline in nature. The optical band gap of the films was tailored between 3.2 and 3.45 eV by varying Mg mole concentration between 0.05 and 0.3. I–V characteristics showed decrease in current with increase in the Mg mole concentration. These results explore the applicability of MgZnO to form effective and efficient heterostructures with ZnO as an active layer for efficient carrier confinement in light emitting devices.     

Optoelectronic properties of CdTe/Si heterojunction prepared by pulsed Nd:YAG-laser deposition technique

The present study is on the optoelectronic properties of isotype CdTe/c-Si heterojunction photodetector made by deposition of CdTe by pulsed laser deposition (PLD) technique on clean monocrystalline Si. Optical, electrical and structural properties of grown CdTe film were investigated. The optical data show that the optical band gap of CdTe was around 1.45 eV at 300 K. The CdTe/Si junction exhibits fair diode rectification and the soft breakdown occurred at V_B>9 V. Dark and illuminated I–V characteristics of the CdTe/Si photodetector are examined at room temperature. The photodetector showed good photosensitivity in the visible and near-infrared regions with a value as high as 0.5A/W at 950 nm.     

The effect of Mg and Al co-doping on the structural and photoelectric properties of ZnO thin film

Mg–Al co-doped ZnO thin films were prepared via radio-frequency reactive magnetron sputtering technique. X-ray diffraction investigation showed all the thin films with different Mg:Al ratio had hexagonal wurtzite structure. All the thin films showed (100) preferential orientation of ZnO. When Al concentration was kept constant but Mg concentration was increased, the grain size decreased at first and then increased. When Mg:Al ratio was 3:1, the grain size reached a maximum. Ultraviolet–visible spectra showed the thin films had a high average transmittance of 80% in the visible range. The optical band gaps of the thin films were obtained as follows: 3.31, 3.32, and 3.37 eV, corresponding to the Mg:Al ratio of 0:1, 1:1, and 3:1, respectively. Photoluminescence spectroscopy showed all the thin films had four main peaks located at 386, 410, 463, and 499 nm. The origin of blue peak is oxygen vacancy. When Mg concentration was kept constant but Al concentration was increased, I–V curve presented that for both of the heterojunctions the rectifying behavior was formed. The conductivity of Mg:Al=1:1 thin film is higher than that of Mg:Al=1:0 thin film. After illumination, light I–V curve deviated from rectifying character.