Dependent Current-voltage Characteristics Research Articles

Observation of doping-induced spin–orbit coupling in gold cluster assembly to carrier-tuneable semiconductors and Schottky behaviors

The doping influenced carrier dynamics to maneuvering n-type to p-type semiconducting gold cluster assembly have been assessed. The resonance photoemission spectroscopic measurements corroborate an incremental rise in the density of states at the valence edge, the overlap of valence states due to doping, and the presence of distinct spin–orbit splitting and coupling in manganese-doping (Au7Mn) compared to gold clusters (Au8), originating from the relativistic effect resulted in a semiconducting property. The work function dependent current–voltage characteristics in metal–semiconductor configuration show Ohmic and Schottky behaviors assorting p-type carriers in Au7Mn in contrast to the n-type Au8 and are presenting an atomic cluster based fast electronic device.

Role of temperature on CdS and MoS2 doped SnO2 nanostructures: Potential applications in photodetection and temperature dependent current-voltage characteristics

The optical and electrical measurements in higher temperatures regime is a crucial issue. Although efforts are made to obtain optical and electrical characteristics at higher temperatures which have been achieved by optimizing various factors like (i) Type and dimensionality of the detecting materials (ii) operating wavelength and (iii) temperature regime. The present study investigates the role of temperature on the performance of an opto-electrical device derived from the nanostructure of a semiconductor oxide (SnO2) and chalcogenides (CdS and MoS2) along with their doped nanostructures. The proposed opto-electrical device is designed to make it simple, accurate, easy to operate, and cost-effective with enhanced performances at elevated temperature ranges from 30 ºC to 120 ºC. The optimized photodetection performance demonstrates its photoresponsivity of ∼6.3 mA W−1 for 390 nm wavelength. Other performance parameters such as detectivity of ∼8 × 108 jones at 405 nm wavelength and quantum efficiency ∼0.676 mA/Wm. The parameters obtained from synthesized material are superior to reported data. Improved photodetector performance is attributed due to the better structural, electronic, optical, and thermal behaviour of the nano dimension of chalcogenides (CdS, MoS2) and semiconductor oxide (SnO2). Apart from photodetection, electrical measurements were also carried out at varying temperature ranges from 30 to 120 ºC. The role of temperature was first evaluated using temperature dependent photoluminescence within the temperature regime (0–90 ºC). Although operating temperature above 90 ºC is a major issue for not allowing the device to operate above 120 ºC to avoid overheating the device and this limits it to show its best performance. The temperature dependent opto-electrical phenomenon was explained with the help of charge transfer across the interface between a silver electrode and nanostructures where dimensionality, operating temperature and nanostructures contribute significantly to the device performance. Hence, a trade-off is made with improved detection performance and operating temperature to qualify the expectations of the device to be competitive which has been justified through experimental results.

Two-dimensional multiband superconductivity of the optimally and uniformly Li-intercalated FeSe nanoflakes

We investigated the electrical transport properties of optimally Li+-intercalated FeSe nanoflakes. Using solid electrolyte gating, we obtained high and uniform electron doping up to ∼0.55 electrons per Fe sites in the FeSe nanoflakes, which exhibit a sharp superconducting transition at Tc ∼45.0 K. The temperature and magnetic-field dependent current-voltage characteristics clearly revealed the two-dimensional nature of the superconductivity in the intercalated FeSe nanoflakes. From the self-field critical current measurements, we found two distinct isotropic superconducting gaps with different gap ratios. These findings suggest that the highly electron-doped FeSe hosts two interband pairing channels between the hybridized electron pockets, in contrast to the case of pristine FeSe with electron and hole pockets.

Geometry dependent current–voltage characteristics of T-stub zigzag-edged graphene nanoribbon quantum waveguides

Geometry dependent current–voltage characteristics of T-stub zigzag-edged graphene nanoribbon quantum waveguides

The temperature dependent current-voltage characteristics of chemically prepared AL/(P)PBS Schottky barrier junction

Zinc (Zn) doped nanocrystalline lead sulphide (PbS) thin film is prepared by chemical bath deposition (CBD) method at bath deposition temperature 313K using Zinc Acetate, Lead Acetate and Thiourea. The prepared films is characterized by X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX), Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis. Al/(p)PbS Schottky barrier junctions are fabricated onto indium tin oxide (ITO) substrate to study the junction parameters. The Current-Voltage (I-V) characteristics of the junctions is measure in the temperature range of 303 to 333 K and various junction parameters are calculated. The ideality factor (n) and Schottky barrier height ( ) b at different temperatures are found to vary from 5.31 to 4.47 and 0.749 eV to 0.755 eV respectively. The carrier concentration is determined from the capacitance-voltage (C-V) plot and found to be of the order 1016cm-3 .

Characteristics of Al/Ge Schottky and ohmic contacts at low temperatures

Schottky barrier contact has been fabricated by thermal deposition of Al on (100) p-Ge (impurity concentratioñ1010/cm3 at 80K) that shows n-type conductivity above 180K due to thermally generated carriers. Both p and n-type Ge exhibits ideal Schottky behavior with low reverse current and near unity ideality factors obtained from the linear form of temperature dependent current-voltage (I–V) characteristics. The diode current at various temperatures change its direction at non-zero applied bias that reflects a shift in position of charge neutrality level (CNL) from the Fermi level of Ge. With the rise in temperature, Schottky barrier height (SBH) steadily increases for p-Ge that can be understood on the basis of observed variation in CNL. Values of SBH determined from the zero bias Richardson plot agrees well with that estimated from the Schottky-Mott rule for strongly pinned interface. Activation energies are determined from the Richardson plot at various forward voltages and found to decrease with applied bias for n-Ge but reduces to zero for p-Ge that shows work function similar to Al. Annealing of Al/Ge induces regrowth of p-type Al doped Ge layer that exhibits gradual reduction of Al concentration towards p-Ge crystal. Al doped Ge (p+)/Ge (p) junction thus fabricated shows linear I–V characteristics in the extrinsic region (below 180K). In the intrinsic region (above 180K), rectification is observed in the I–V curve due to temperature dependent change in conductivity of both Al doped Ge layer and Ge crystal.

Thickness dependent photocurrent spectra and current-voltage characteristics of P3HT:PCBM photovoltaic devices.

P3HT:PCBM based photovoltaic devices with different active layer thicknesses (ALTs) were examined in photodetector and solar cell operation modes. The photodetector photocurrent spectra and solar cell current density-voltage characteristics were measured. All experimental results were reproduced by the unique drift-diffusion model which excludes the optical interference and allows the parameters of photogeneration, transport, and recombination to be ALT dependent. The active layer optical characterization indicated a thickness dependence of optical parameters too. A conclusion was drawn that the P3HT:PCBM film thickness and morphology are strongly correlated which leads to a non-monotonic change of film parameters with its thickness.

Effects of post-deposition CdCl2 annealing on electronic properties of CdTe solar cells

The effects of post-deposition CdCl2 annealing temperature on the electronic properties of CdTe solar cells were investigated. CdTe devices incorporate Mg doped ZnO as a buffer layer and selenization using a CdSe interlayer for reducing the buffer/absorber interface recombination and increasing solar energy absorption respectively. The post-deposition CdCl2 annealing treatments were done under separate, inert atmospheres of nitrogen and helium across the temperature range 380–430 °C. Electrical characterization of devices is carried out including temperature dependent current-voltage characteristics, admittance spectroscopy, and Shockley-Read-Hall recombination analysis. The best improvements in device efficiency are obtained upon annealing at temperature 410 °C. This anneal correlated with reduced back contact barrier in CdTe and reduced grain-boundary barrier height which is beneficial for enhanced charge transport.

Wavelength dependent photosensitivity modulation of Aluminium/Lead sulphide/Indium tin oxide back-to-back diode

The photosensitivity of aluminium (Al)/lead sulphide (PbS)/indium tin oxide (ITO) thin layered structure is investigated considering the photon wavelength dependent current-voltage and capacitance-voltage characteristics of the device. The current-voltage characteristics of the test structure are analyzed adopting the back-to-back Schottky barrier diode model. The diode possesses low dark current in contrast to the high value of photocurrents measured under different illumination wavelengths. The change in photocurrents with different illumination wavelengths clearly indicates the change in photo-sensitivity of the device. The capacitance-voltage characteristics of Al/PbS/ITO structure demonstrate a definite improvement of the device capacitance with the higher wavelength exposures. The matter is explained in terms of the additional capacitance owing to the excess carrier generation within the device under illumination. The photosensitivity modulation of the device can be exploited in photo-sensor or photo-detector applications in various electronic devices.

Temperature dependent current–voltage characteristics of Ag/Zn2GeO4/Si diode grown by thermal evaporation method

In this manuscript, we have investigated the transport properties of Ag/Zn2GeO4/Si Schottky diode using temperature dependent current–voltage (I-V) characteristics. The ZnO sample was grown on Si substrate was fabricated by home developed thermal coating unit. The silver (Ag) metal contact of diameters 0.78 mm2 was fabricated on grown Zn2GeO4 and was studied comprehensively using pico meter over temperature range of 120 K–425 K. The I-V data demonstrated that ideality factor decreased from 6.2 to 2.0 and barrier height increased from 0.3 to 0.8 eV as the measurement temperature increased from 120 to 425 K respectively. The data demonstrated the presence of inhomogeneity at the interface of Ag metal and Zn2GeO4 semiconductor. To explain the barrier height inhomogeneity, we have further process the data by plotting different graphs between ideality factor versus barrier height and 1/2kT versus barrier height. The graph between ideality factor and barrier height gives a homogenous barrier height of 0.6 eV. Barrier height versus 1/2kT plot was drawn to obtain the values of mean barrier height for 0.75 eV and standard deviation (δs) 0.016 V at zero bias respectively.

Analysis of the Current-Voltage Hysteresis Behavior of Polyvinyl Alcohol-Zinc selenide Nanocomposite Film

The temperature dependent current-voltage characteristics of the Polyvinyl Alcohol-Zinc selenide nanocomposite films were studied in the voltage window of -5V to +5V. It was observed that with the increase in applied voltage and temperature, the current-voltage characteristics shift from ohmic to non-ohmic nature and show hysteresis behavior. It has also been observed that the sample resistance changes from low resistance state (LRS) to high resistance state (HRS) depending on the applied voltage and temperature. The observed phenomenon has been analyzed based on the available theoretical models to elucidate the prevailing current conduction mechanism.

Experimentally Validated Hopping-Transport Model for Energetically Disordered Organic Semiconductors

Charge transport in disordered organic semiconductors occurs by hopping of charge carriers between localized sites that are randomly distributed in a strongly energy dependent density of states. Extracting disorder and hopping parameters from experimental data like temperature dependent current-voltage characteristics typically relies on parametrized mobility functionals that are integrated in a drift-diffusion solver. Surprisingly, the functional based on the extended Gaussian disorder model (eGDM) has been extremely successful at this, despite it being based on the assumption of nearest neighbor hopping (nnH) on a regular lattice. We here propose a variable range hopping (VRH) model that has been integrated in a freeware drift-diffusion solver. The mobility model has been calibrated using kinetic Monte Carlo calculations and shows good agreement with the Monte Carlo calculations over the experimentally relevant part of the parameter space. The model is applied to temperature-dependent space charge limited current (SCLC) measurements of different systems. In contrast to the eGDM, the VRH model provides a consistent description of both p-type and n-type devices. We find a critical ratio of aNN/$\alpha$ (mean inter-site distance / localization radius) of ~3 below which hopping to non-nearest neighbors becomes important around room temperature and the eGDM cannot be used for parameter extraction. Typical (Gaussian) disorder values in the range 45-120 meV are found, without any clear correlation with photovoltaic performance when the same active layer is used in an organic solar cell.

Exploring ultrafast threshold switching in In3SbTe2 phase change memory devices

Phase change memory (PCM) offers remarkable features such as high-speed and non-volatility for universal memory. Yet, simultaneously achieving better thermal stability and fast switching remains a key challenge. Thus, exploring novel materials with improved characteristics is of utmost importance. We report here, a unique property-portfolio of high thermal stability and picosecond threshold switching characteristics in In3SbTe2 (IST) PCM devices. Our experimental findings reveal an improved thermal stability of amorphous IST compared to most other phase change materials. Furthermore, voltage dependent threshold switching and current-voltage characteristics corroborate an extremely fast, yet low electric field threshold switching operation within an exceptionally small delay time of less than 50 picoseconds. The combination of low electric field and high speed switching with improved thermal stability of IST makes the material attractive for next-generation high-speed, non-volatile memory applications.

Temperature- and pulse-dependent negative differential resistances in ZnO/Nb:SrTiO3 heterojunctions

Temperature- and pulse amplitude/width dependent current-voltage characteristics were performed to study the variance of negative differential resistance (NDR) features accompanying bipolar resistive switching. Interestingly, the absolute value of the NDR peak intensity is enhanced at first and then weakened, while the NDR peak position gradually shifts toward the lower absolute bias value with an increase in temperature from 140 to 300 K, and shifts toward the larger absolute bias value with an increase in temperature from 300 to 400 K. Furthermore, the NDR peak is absent after applying a small and narrow positive pulse, while it gradually increases with increasing the applied pulse amplitude or width. These temperature- and pulse-dependent NDR behaviors can be fully understood based on a model of generation and drift of ionized oxygen vacancies coupled with trapping/detrapping electrons. The clarification of the mechanism will pave the way for practical applications.

Effect of thermodynamic glass transition on charge transport properties in a benzodithieno-imidazole π-conjugated polymer: fullerene blend

In this work, the charge transport properties of bulk heterojunction formed by p-type benzodithieno-imidazole (BDTI-Br) based π-conjugated polymer and PCBM acceptor has been investigated in photovoltaic configuration under dark conditions. Temperature dependent current-voltage (J − V) characteristics show a transition from ohomic () to trap dominated space charge limited current with a power law J ∼Vm, m ≥ 2 for higher applied voltages. Capacitance-voltage measurement shows that capacitance value at reverse bias is drift controlled and the accumulation of diffused charge carriers contribute at forward bias. An equivalent impedance model gives charge carrier lifetime values in milliseconds and electron mobility values in the range of ∼10−5 cm2 V−1 s−1; in line with that obtained by charge extraction by linearly increasing voltage method. The extrapolated dc conductivity values in 113 K–473 K show Arrhenius like behavior with an activation energy of 145 meV. Notable changes in temperature dependent conductivity, carrier concentration and carrier mobility values around 320 K indicate a strong correlation of charge transport process with structural changes that may occur in bulk heterojunction around its thermodynamic glass transition temperature.

Field Plating for Improved Ga2O3 Schottky Rectifier Performance

Ga2O3­ rectifiers have the potential to surpass SiC and GaN diodes due to the ultrawide-bandgap of 4.9 eV. In this context to reach the maximum potential for Schottky rectifiers, electric field mitigation techniques must be used to optimize performance. In this study, the effects of various dielectric field plates (SiO2/SiN, Al2O3/SiN, HfO2/SiN) on device performance of circular Ga2O3 Schottky rectifiers was investigated. The rectifiers were fabricated on 10 µm, lightly doped (n = 2.8 × 1016 cm-3) β-Ga2O3 epitaxial layers grown by Hydride Vapor Phase Epitaxy on conducting substrate (n = 4.8 × 1018 cm-3) grown by Edge-Defined, Film-Fed growth. Temperature dependent forward current-voltage characteristics were used to extract the average Schottky barrier height of 1.14 eV ± 0.03 eV for Ni, average ideality factor of 1.02 ± 0.02, and the Richardson’s constant of 48.1 A/cm2K2. The reverse breakdown and leakage current were the two characteristics which were predominantly affected by the field plate dielectrics. The highest reverse breakdown reached was 730 V for Al2O3/SiN, which was significantly higher than SiO2/SiN and HfO2/SiN, 562 V and 401 V, respectively. Electric field modeling was used to determine the location of peak electric field and was found to occur at the edge of the field plate, which agreed with experimental observations of breakdown induced defects occurring on the edge of the device. The on-resistance ranged from 3.8-5.0 × 10-3 Ω-cm2 which was dependent on diode size, diameters from 50 to 200 µm. This led to a power figure-of-merit (VB 2/RON) of 1.4 × 108 W-cm2.

Barrier height inhomogeneities on Pd/n-4H-SiC Schottky diodes in a wide temperature range

Barrier height inhomogeneities on Pd/n-type 4H-SiC Schottky barrier diodes in the 300–800 K temperature range have been investigated. Palladium is known to form silicide above 673 K. Temperature dependent current-voltage (I-V) characteristics were analyzed. Barrier height (BH) and ideality factor (n) were found to be strongly temperature dependent. Barrier height increased, whilst ideality factor decreased with increasing in temperature and the Richardson plot showed some deviation from linearity. This was attributed to barrier inhomogeneities at the metal-semiconductor interface which resulted in a distribution of barrier heights. From the modified Richardson plot, the modified Richardson constant, A** was found to be 155 Acm−2K−2 and 87 Acm-2 K−2 in the 300–525 K and the 550–800 K temperature ranges respectively.

Effects of reduced internal electric field in InGaN/pseudo-AlInGaN multi-quantum-well on forward leakage current and photocurrent properties

The main focus of this work is to find the effects of the internal electric field on the forward leakage current and photocurrent of an InGaN/pseudo-AlInGaN multi-quantum-well (MQW) grown on sapphire substrate using metalorganic chemical vapor deposition. The temperature dependent current-voltage characteristics of an InGaN MQW with and without an AlInGaN barrier (sample A = GaN barrier, sample B = Al0.043In0.036Ga0.921N barrier, sample C = Al0.043In0.052Ga0.905N) exhibit two linearly dependent divisions with different slopes at low (1.0 ≤ V ≤ 1.4) and medium (1.6 ≤ V ≤ 2.5) bias regions in the 250–300 K range. The temperature-insensitive behavior of the characteristic energy and large ideality factors mean that tunneling is the dominant process in the three samples. Distinct tunneling entities at low and medium biases are observed for samples A and B; however, for sample C, thermionic emission gain dominance in the medium bias range. The peculiar behavior in sample C is attributed to suppressed hole-tunneling currents caused by a low internal electric field. Photocurrent experiments using a xenon lamp demonstrate that sample C exhibit higher photocurrent characteristics and that the enhanced photocurrent is due to a reduced internal electric field. The low internal electric field generates a large amount of photo-excited carriers, which cross the potential of QW effectively compared to the conventional GaN barrier.

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.

Analysis of Schottky emission electric charge transport mechanism in Cu-Lu2O3-Cu MIM structure by temperature dependent current-voltage characteristics

In this study, the Cu-Lu2O3-Cu metal-insulator-metal (MIM) structure was fabricated by electron beam evaporation method on the glass substrate with symmetric electrode configuration. The dominant conduction mechanism in fabricated MIM diode was analyzed using temperature dependent current-voltage (I-V) characteristics in temperature range 323–403 K. Schottky emission, Fowler-Nordheim (F-N) and Poole-Frankel (P-F) conduction mechanisms were tested by analyzing the I-V data according to these theories. P-F emission and Schottky emission conduction mechanisms were found to be dominant conduction mechanisms in low and high applied electric field range respectively. The Schottky emission mechanism was further studied in detail by plotting the Ln(I/T2) Vs V1/2 and Ln(I/T2) Vs 1000/T plots at different applied fields and temperatures respectively. The dielectric constants were extracted from the conduction plots at various temperatures and were found to be close agreement with experimental dielectric constant of Lu2O3 (11). The metal-insulator barrier height and trap energy were also calculated at various measurement temperatures and discussed according to Schottky emission theory.