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.     

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.     

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.     

Current conduction mechanism of MIS devices using multidimensional minimization system program

The present work presents an evaluation approach which enables the in-depth analysis of current–voltage (I–V) characteristics of MIS devices to determine their current transport mechanisms using a multidimensional minimization system program.Exemplarily, the current transport mechanisms were determined for a TiN/SiO₂/p-Si MOS and a TaN/HfSiO/SiO₂/p-Si MIS structure by fitting the analytical expressions for different current transport mechanisms to experimental I–V data in a wide range of applied biases and temperatures. The considered mechanisms for the investigated samples include temperature dependent Fowler–Nordheim (FN) tunneling and Poole–Frenkel (PF) emission as well as ohmic conduction. The presented approach can easily be extended to account for additional mechanisms such as trap assisted tunneling (TAT) if relevant for different samples. In contrast to typical extraction procedures which determine current conduction mechanism parameters sequentially, in this work, the adjustable fit parameters are extracted in a single operation using the Levenberg–Marquardt algorithm (Nash, 1990) to obtain a least-square fit of the model to measured I–V characteristics. Thus, simultaneously occurring current mechanisms can properly be evaluated which allows to determine the fraction of each conduction mechanism quantitatively for each voltage.     

X-ray conductivity of ZnSe single crystals

The experimental I–V and current–illuminance characteristics of the X-ray conductivity and X-ray luminescence of zinc-selenide single crystals feature a nonlinear shape. The performed theoretical analysis of the kinetics of the X-ray conductivity shows that even with the presence of shallow and deep traps for free charge carriers in a semiconductor sample, the integral characteristics of the X-ray conductivity (the current–illuminance and I–V dependences) should be linear. It is possible to assume that the nonlinearity experimentally obtained in the I–V and current–illuminance characteristics can be caused by features of the generation of free charge carriers upon X-ray irradiation, i.e., the generation of hundreds of thousands of free charge carriers of opposite sign in a local region with a diameter of <1 μm and Coulomb interaction between the free charge carriers of opposite signs.     

Single-parameter model for the post-breakdown conduction characteristics of HoTiOx-based MIM capacitors

The post-breakdown conduction characteristics of holmium titanium oxide (HoTiO_x)-based metal–insulator–metal capacitors fabricated by the atomic layer deposition technique on Si substrates were investigated. Diode-like and power-law models were fitted to the experimental current–voltage (I–V) curves and the results assessed with the aim of detecting any possible correlation among the model parameters. It was found that the number of parameters involved can be reduced in both cases and that for the power-law model a single parameter is solely required to approximate the I–V curves in a wide current range (from 10⁻¹¹ to 10⁻⁴ A). This property, which has also been observed in a variety of material systems, was used to simulate the bipolar switching behavior exhibited by the I–V characteristics. The connection with the physics of electron transport through atom-sized constrictions is discussed.     

Temperature dependences of surface recombination DC current–voltage characteristics in MOS structures

Temperature dependences of recombination current at interface traps in MOS transistor structure are investigated using the Shockley–Read–Hall Recombination DC current–voltage (R-DCIV) characteristics. Results include the effects of energy distribution of the interface traps (discrete, constant and U-shaped energy distributions) on the temperature dependence of the base terminal current-vs-gate-voltage lineshape (I_B–V_GB), the peak current and voltage (I_B-peak, V_GB-peak) and their thermal activation energy E_A, and the reciprocal slope n of the I_B-peak vs base/drain (or base/source) p/n junction forward voltage V_BD. Surface impurity concentration and oxide thickness are varied. Temperature dependence of E_A, V_GB-peak and n is small while I_B-peak and R-DCIV linewidth, large. This small temperature dependence simplifies the experimental implementation and data analysis of R-DCIV methodology applied at room temperatures without using expensive temperature controlled wafer-probe station.     

Electronic and Magneto-Transport Across the Heusler Alloy (Co2FeAl)/p-Si Interfacial Structure

Electronic and magneto-transport across the Heusler alloy Co₂FeAl (CFA)/ p-Si structure have been studied. The morphology of the Heusler alloy film surface has also been characterized by atomic force microscopy and magnetic force microscopy (MFM). X-ray diffraction data revealed formation of the CFA alloy phase with the L2₁ structure. MFM results revealed formation of a fine domain structure of average size ～10 nm and magnetic signal strength 0.23°. The I–V characteristics are strongly temperature-dependent between ～80 K and 300 K for forward bias, compared with weak temperature dependence on reversing the polarity. At low temperature the I–V characteristics have the features of a backward diode. The observed strong temperature dependence is because of thermionic emission of carriers across the interface. The weak temperature dependence is because of dominant field-emission tunnelling of carriers across the interface. Large magnetic field sensitivity of the reverse current has also been observed. The observed magnetic field sensitivity for the reverse current shows the involvement of electronic spin in transport across the interface, from the Heusler alloy to the silicon. An MR of ～35% in the presence of a magnetic field was estimated from the I–V data. The study has shown that spin-dependent tunnel transport from the CFA alloy to silicon across the interface results in the observed value of MR, which seems to be because of spin scattering.     

Electrical Properties and Current Transport Mechanisms of the Au/n-GaN Schottky Structure with Solution- Processed High-k BaTiO3 Interlayer

The electrical properties and current transport mechanisms of Au/BaTiO₃ (BTO)/n-GaN metal–insulator–semiconductor (MIS) structures have been investigated by current–voltage (I–V) and capacitance–voltage (C–V) measurements at room temperature. Experimental results reveal that the MIS structure has a higher rectification ratio with low reverse leakage current compared with the Au/n-GaN metal–semiconductor (MS) structure. The calculated barrier height of the Au/BTO/n-GaN MIS structure [0.87 eV (I–V)/1.02 eV (C–V)] increases compared with the Au/n-GaN MS structure [0.73 eV (I–V)/0.96 eV (C–V)]. The series resistance is extracted using Cheung’s functions, and the values are in good agreement with each other. Furthermore, the energy distribution of the interface state density is estimated from the forward-bias I–V data. It is noteworthy that the interface state density of the MIS structure is lower than that of the MS structure. In both MS and MIS structures under forward-bias conditions, ohmic and space-charge-limited conduction mechanisms are identified at lower and higher voltages, respectively. Investigations reveal that Poole–Frenkel emission dominates the reverse leakage current in both Au/n-GaN and Au/BTO/n-GaN structures.     

Interface instabilities in polymer light emitting diodes due to annealing

In polymer light emitting diodes (PLEDS) with an (ITO/PPV/Ca) structure we observed a significant reduction of both the current and the light output at constant voltage after heat treatment for only 30 min at 65 °C. Electroluminescence spectroscopy experiments showed that the shape as well as the amplitude of the spectra were changed.The reduction of current and light output was investigated by measuring I–V and E–V (current–voltage and brightness–voltage) characteristics of PLEDs, I–V characteristics of single carrier devices, and by performing low energy ion scattering and X-ray photoelectron spectroscopy experiments on the Ca/PPV interface.It was concluded that the current and light output reduction could be ascribed to the degradation of the Ca/PPV and the ITO/PPV interfaces. The degradation of the ITO/PPV interface resulted in a reduction of the zero field hole mobility and a small increase of the field dependence of the mobility. The degradation of the Ca/PPV interface, probably by diffusion of calcium into the PPV, resulted in carrier traps and quenching sites, which influenced the field dependent electron mobility.     

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.     

Nonlinear HEMT model formulated from the second-order derivative of the I-V and Q-V characteristics

In this paper, an empirical nonlinear model of high electron mobility transistors (HEMTs) suitable for a wide bias range is presented. Unlike the conventional large-signal models whose fitting parameters are coupled to the measured drain current and gate capacitance characteristics, the derived modeling equations are direct formulated from the second-order derivative of drain current (I-V) and gate charge (Q-V) with respect to gate voltage. As a consequence, the proposed nonlinear model is kept continuously differentiable and accurate enough to the higher-order I-V and Q-V derivatives. Besides, the thermal and trapping effects have been implemented in the large-signal model along with its dependence on temperature and quiescent-bias state. The composite nonlinear model is shown to accurately predict the S-parameters, large-signal power performances as well as the two-tone intermodulation distortion products for various types of GaAs and GaN HEMTs.     

Characterization of p-CdTe/n-CdS hetero-junctions

Nano-crystalline CdTe/CdS thin film hetero-junctions have been grown on glass substrate by thermal evaporation technique. The growth conditions to get stoichiometric compound films have been optimized. The grown hetero-junctions have been characterized for their I–V characteristics. Analysis of I–V characteristics has been made to investigate the current conduction mechanism in p-CdTe/n-CdS hetero-junction. The band gap energy of cadmium telluride and cadmium sulfide films have been computed from the study of variation of resistance with temperature. Based on the study, band diagram for p-CdTe/n-CdS hetero-junction has been proposed.     

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.     

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.     

Fabrication,structural and electrical characterization of AlNi2Si based heterojunction grown by LPE

This work elucidates the applicability for Liquid-Phase Epitaxy (LPE) to grow epilayers of AlNi₂Si on single crystalline Si with a good crystalline quality and low series resistance. Surface morphology and crystalline structural characteristics of the heterojunction were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. Temperature dependence of the current–voltage (I–V) characteristics is studied to elucidate the predominant conduction mechanism in the temperature range 305–370 K. Heterojunction parameters such as ideality factor, series resistance, barrier height show temperature dependence in the desired temperature range. Cheung functions are applied for determination the heterojunction parameters and compared with each other. Temperature dependence of capacitance–voltage (C–V) characteristics was considered. The built-in potential, net carrier concentration, maximum barrier height, maximum barrier field and the width of the depletion region obtained from the C–V measurements were studied as a function of temperature.     

Inhomogeneous Ni/Ge Schottky barriers due to variation in Fermi-level pinning

To achieve high performance Ge nMOSFETs it is necessary to reduce the metal/semiconductor Schottky barrier heights at the source and drain. Ni/Ge and NiGe/Ge Schottky barriers are fabricated by electrodeposition using n-type Ge substrates. Current (I)–voltage (V) and capacitance (C)–voltage (V) and low temperature I–V measurements are presented. A high-quality Schottky barrier with extremely low reverse leakage current is revealed. The results are shown to fit an inhomogeneous barrier model for thermionic emission over a Schottky barrier. A mean value of 0.57 eV and a standard deviation of 52 meV is obtained for the Schottky barrier height at room temperature. A likely explanation for the distribution of the Schottky barrier height is the spatial variation of the metal induced gap states at the Ge surface due to a variation in interfacial oxide thickness, which de-pins the Fermi level.     

Sodium-peak splitting in dynamic current-voltage characteristics of convective ion currents in metal-oxide-semiconductor structures

The results of simultaneous measurements of dynamic current-voltage and capacitance-voltage characteristics are presented for metal-oxide-semiconductor structures in the temperature range T = 420–470 K and voltage-sweep rates β _v = 0.5–1000 mV/s. The convective currents I _con (V) in oxide are extracted from usual ion currents in the I-V characteristics. In I _con (V) curves, the Na⁺-ion peaks are split. In addition, an envelope curve is seen in initial portions of “fast” I _con(V) curves with β _V ? 10 mV/s that indicates to the presence of a certain quasi-steady ion-transport mode. A more equilibrium mode at slow rates β _V < 1 mV/s manifests itself in the form of stabilization of convective-current peak shapes. The nature of efficient neutralization of the second peaks in the I _con(V) dependences is discussed.     

Electronic structure and current injection in zinc phthalocyanine doped with tetrafluorotetracyanoquinodimethane: Interface versus bulk effects

The p-type doping of zinc phthalocyanine (ZnPc) with the highly electronegative tetrafluorotetracyanoquinodimethane (F₄-TCNQ) is investigated via direct and inverse photoemission spectroscopy and in situ current–voltage (I–V) measurement. The electron affinity of F₄-TCNQ and the ionization energy of ZnPc are found to be energetically compatible with an electron transfer between the highest occupied molecular orbital (HOMO) of the host and the lowest unoccupied molecular orbital of the dopant. The Fermi level is near mid-gap in undoped ZnPc, and drops to 0.42 and 0.18 eV above the HOMO in the 0.3% and 3% doped films, respectively, consistent with efficient p-doping. The dependence of the Au/ZnPc:0.3%F₄-TCNQ/Au I–V characteristics on the thickness of the organic film is analyzed in terms of injection-limited versus space-charge-limited current. The analysis demonstrates that the large doping-induced increase in hole current is primarily due to improved carrier injection via tunneling through the narrow interface space charge layer.