Apparent Barrier Height Research Articles

Modelling and Analysis of Inhomogeneous Back-to-Back Schottky Junction Diode

Back-to-back Schottky diode (BBSD) is a simple device structure made from Schottky junctions that can be applied in various applications. In modelling and simulating the BBSD, the inhomogeneity of the barrier height at the Schottky interface should be considered. This paper presents device models and simulation result of an inhomogeneous BBSD. Two device models with different current spreading condition are considered. The distribution of the inhomogeneous barrier height is represented by Gaussian distribution. All the computation was done using Python programming software. When the standard deviation of the barrier height increases, the apparent barrier height that influence the electrical characteristic decreased. This is consistent with the reported experimental data. Device model that considers full current spreading showed 37.8% reduction of apparent barrier height at standard deviation of 100 meV. This is greater that the model with no current spreading. The ideality factor showed correlation with the standard deviation of barrier height, particularly when no current spreading is considered. At standard deviation of 100 meV, the ideality factor increased 2.6 %. The obtained non-unity ideality factor is associated to the significant fluctuation in the barrier height. The computed temperature-dependent current curves also showed good agreement with the reported experimental results. The device model can be a convenient tool to investigate the device operation and to validate the method used for extraction of Schottky barrier parameters.

The probe of current conduction mechanisms, interface states, and the forward bias intersection point of the al/Al2O3/Ge/p-Si heterostructures depending on temperature

The current conduction mechanisms (CCMs), temperature-sensitivities (S), energy-dependent interface traps (Nss), and origin of the intersection points in the forward bias (IF−VF) plots of the Al/Al2O3/Ge/p-Si heterostructure were investigated in wide temperature range of 90–420 K. Firstly, main electrical parameters, including reverse-saturation current (Io), ideality factor (n), zero-bias barrier-height (ΦBo), and series-resistance (Rs) values, were extracted for each temperature. The lnIF-VF curves illustrate two distinct linear regimes at low and intermediate bias voltages. Despite the observed decline in n values as temperature rises, the corresponding ΦBo values exhibit an upward trend. The conventional Richardson plots deviated from linearity at low temperatures, and the Richardson-constants (A*) value obtained from its linear part is quite lower than its theoretical value. Hence, ΦBo−q/2 kT, ΦBo−n, and n(kT)/q−(kT/q) correlations were plotted to seek indications of the Gaussian distribution (GD) of barrier heights (BHs) and tunneling mechanism. Temperate sensitivity (S = dV/dT) for 0.01, 0.10, 0.50, and 1 μA was found as 2.30, 2.33, 2.34, and 2.35 mV/K, which indicated that the fabricated Al/Al₂O₃/Ge/p-Si heterostructure is highly sensitive to temperature, rendering it suitable for use in temperature sensor applications. The observed crossing point at about 2.4V was explained by an increase in the apparent BH with temperature and the presence of Rs.

Insights into factors that affect non-Arrhenius migration of a simulated incoherent Σ3 grain boundary

Non-Arrhenius grain boundary migration, sometimes referred to as antithermal migration where temperature and GB velocity values are inversely related to each other, is examined in an incoherent twin Σ3 [111] 60° (11 8 5) nickel grain boundary. Molecular dynamics is used to simulate migration and examine the effect of various factors on the migration, including interatomic potential, system size, driving force, and variation of atomic grain boundary structure. A classical model for grain boundary migration, in its unsimplified form, is used to analyze the results. The grain boundaries exhibit migration mechanisms with very low apparent barrier heights to migration. As a result, the boundaries migrate quickly but exhibit a velocity saturation similar to that of dislocations. The various interatomic potentials exhibit different migration velocities, but their similarities suggest they all predict similar overall behaviors of migration. The variation of atomic structure in the same incoherent twin grain boundary leads to diverse behaviors with barrier heights that vary from non-Arrhenius to Arrhenius migration. Facet nucleation is confirmed not to be a requirement for this boundary based on an examination of simulation cell size; however, the presence and/or interaction between numerous facets does suggest a slowing and increased barrier height to migration for larger boundaries.

Electrical properties of Cu/Pd2Si Schottky contacts to AlGaN/GaN-on-Si HEMT heterostructures

In this study, we analyze gold-free Cu/Pd2Si Schottky contacts to AlGaN/GaN-on-Si HEMT (high electron mobility transistor) heterostructures. The silicide layers are fabricated through magnetron sputtering deposition using a stoichiometric Pd2Si target and are subjected to post-gate annealing at different temperatures. After annealing at 500 °C the leakage currents of the planar diodes are reduced below 3.2 mA/cm2. The microstructures of the diodes are analyzed through transmission electron microscopy (TEM). The post-gate annealing increases lateral dimensions of silicide grains. The electrical properties of the contacts are determined by performing temperature-dependent current-voltage (I-V-T) measurements. The forward current exhibits a specific voltage dependence, which is interpreted based on the two-diode model, reflecting the properties of the Pd2Si/heterostructure interface along with those of the heterostructure itself. The model is fitted to extract the parameters of the Schottky contacts. The barrier height of 0.91 eV and ideality factor n = 1.5 are obtained after post-gate annealing at 500 °C. The effects of post-gate annealing on the forward conduction and leakage mechanisms are then discussed. A simple method is proposed to estimate the polarization charge density, which is required to calculate the electric fields in the heterostructure in the reverse bias. It is observed that post-gate annealing affects the I-V characteristics, likely by reducing the density of the unintentional donors and trap states, leading to an increase in the apparent barrier height along with a reduction in the density of defects contributing to the leakage current.

Engineering the Schottky Interface of 3.3 kV SiC JBS Diodes Using a P<sub>2</sub>O<sub>5</sub> Surface Passivation Treatment

A systematic study is presented into the impact of a P2O5 surface passivation treatment, carried out prior to the deposition of a high refactory metal contact to 3.3 kV JBS diodes. Electrical results from Mo, W and Nb diodes reveal that those diodes that undergo the treatment have a major leakage current reduction, most significantly by 3.5 orders of magnitude to 1.5×10-6 A.cm-2 for treated W diodes. When applied to fully optimized 3.3 kV Mo/SiC JBS diodes, the P2O5 surface passivation treatment reduces the apparent barrier height, as well as the leakage current. SIMS analysis reveals that during the treatment, phosphorous diffuses into the top 10 nm of the SiC, achieving a peak density of 1019 cm-3, while XPS results suggest some of this diffuses into the contact metal during the contact anneal, altering the SBH. TCAD simulations help give more insight into band diagram changes at the Schottky interface, where the partial activation of the phosphorous ions is shown to alter the Schottky barrier, promoting a thermionic field emission conduction, effectively lowering the barrier height at the interface in Mo/4H-SiC diodes.

Electrical transport properties of thermally stable n-ZnO/AlN/p-Si diode grown using RF sputtering

The temperature dependent electrical transport properties of n-ZnO/AlN/p-Si heterojunction diode fabricated by RF sputtering system have been investigated over a wide temperature range of 303 K–413 K. The AlN buffer layer in-between ZnO and Si lowers the mismatch in thermal expansion coefficient/lattice constant for improved electrical and structural characteristics. XRD pattern and FESEM confirm the crystalline nature and good quality of ZnO thin film with uniform grain size and crack free structure respectively. As measured from the temperature dependent I–V curve, the apparent barrier height reduces as Ideality factor rises which shows good thermal stability within the temperature range studied here. The mean value of barrier height as well as the Richardson constant have been evaluated. Additionally, by taking into account the Gaussian distribution of inhomogeneous barrier heights, the modified Richardson constant has been estimated.

Reversible optical control of the metal-insulator transition across the epitaxial heterointerface of a VO2/Nb:TiO2 junction

Optical control of exotic properties in strongly correlated electron materials is very attractive owing to their potential applications in optical and electronic devices. Herein, we demonstrate a vertical heterojunction made of a correlated electron oxide thin film VO2 and a conductive 0.05 wt% Nb-doped TiO2 single crystal, whose metal-insulator transition (MIT) across the nanoscale heterointerface can be efficiently modulated by visible light irradiation. The magnitude of the MIT decreases from ~350 in the dark state to ~7 in the illuminated state, obeying a power law with respect to the light power density. The junction resistance is switched in a reversible and synchronous manner by turning light on and off. The optical tunability of it is also exponentially proportional to the light power density, and a 320-fold on/off ratio is achieved with an irradiance of 65.6 mW cm−2 below the MIT temperature. While the VO2 thin film is metallic above the MIT temperature, the optical tunability is remarkably weakened, with a one-fold change remaining under light illumination. These results are co-attributed to a net reduction (~15 meV) in the apparent barrier height and the photo-carrier-injection-induced metallization of the VO2 heterointerface through a photovoltaic effect, which is induced by deep defect level transition upon the visible light irradiance at low temperature. Additionally, the optical tunability is minimal, resulting from the quite weak modulation of the already metallic band structure in the Schottky-type junction above the MIT temperature. This work enables a remotely optical scheme to manipulate the MIT, implying potential uncooled photodetection and photoswitch applications.

Nanoscale Probing of Image-Potential States and Electron Transfer Doping in Borophene Polymorphs.

Because synthetic 2D materials are generally stabilized by interfacial coupling to growth substrates, direct probing of interfacial phenomena is critical for understanding their nanoscale structure and properties. Using field-emission resonance spectroscopy with an ultrahigh vacuum scanning tunneling microscope, we reveal Stark-shifted image-potential states of the v1/6 and v1/5 borophene polymorphs on Ag(111) with long lifetimes, suggesting high borophene lattice and interface quality. These image-potential states allow the local work function and interfacial charge transfer of borophene to be probed at the nanoscale and test the widely employed self-doping model of borophene. Supported by apparent barrier height measurements and density functional theory calculations, electron transfer doping occurs for both borophene phases from the Ag(111) substrate. In contradiction with the self-doping model, a higher electron transfer doping level occurs for denser v1/6 borophene compared to v1/5 borophene, thus revealing the importance of substrate effects on borophene electron transfer.

Determining the potential barrier presented by the interfacial layer from the temperature induced I–V characteristics in Al/p-Si Structure with native oxide layer

The temperature induced current-voltage (I–V-T) characteristics of the Al/SiO2/p-Si diodes with the interfacial native oxide layer were experimentally investigated in present our study. The values of 24.35 and 1.02 eV for the tunneling factor (aδχ) and the potential barrier presented by the interfacial layer (χ) were determined for the Al/SiO2/p-Si metal-insulator-semiconductor (MIS) diode. The χ value obtained from the forward bias I–V-T characteristics of the SiO2/p-Si diode is a crucial result according to those from only room temperature I–V curves in literature studies. Furthermore, the temperature dependence of the apparent barrier heights of the forward bias I–V-T characteristics displayed a Gaussian distribution (GD) of inhomogeneous barrier heights (BHs). Thus, the standard deviation values of σ1s0=147.65 mV for high temperature range and σ2s0=83.66 mV for low temperature range were obtained from the GD plot of the BHs (the apparent BH versus (2kT)−1 plot). Again, for the mean barrier height Φ‾b0 from the GD plot of the BHs, the values of 1.16 eV and 0.70 eV were obtained from the high temperature region and low temperature region, respectively. Furthermore, the Richardson constant values of 54.66 and 58.42 A/K2cm2 from these temperature regions are approximately 1.70 times higher than the theoretical value of 32 A/K2cm2 of the p-type Si semiconductor.

Gaussian distribution of inhomogeneous nickel–vanadium Schottky interface on silicon (100)

This study presents the characterization of the nickel–vanadium (NiV) Schottky diode on n-type silicon (Si) in the temperature range 75 K–300 K. The experimental current–voltage (I–V) measurements are first analyzed by using the thermionic emission (TE) theory. For this purpose, the vertical optimization method is used to find the values of the TE parameters, i.e. the values of the ideality factor, barrier height, and series resistance. It is found that these parameters exhibit strong temperature dependence, i.e. an increase of the ideality factor and a decrease of the barrier height and the series resistance when the temperature decreases, which is due to inhomogeneities at the Schottky interface. Therefore, we employ Werner’s model under the assumption of a Gaussian distribution to analyze the temperature dependence of the TE parameters. The mean and standard deviation of the barrier height are obtained as and , respectively. In addition, we show that the apparent barrier height and apparent ideality factor are in accordance with Werner’s model. Furthermore, we use the modified Richardson plot to find the value of the Richardson constant. The obtained value of the latter is A cm−2 K−2 and is very close to the theoretical value of 112 A cm−2 K−2 of n-type Si. Finally, we investigate the temperature dependence of the ideality factor and show the validity of the T0-effect for the NiV/Si Schottky diode.

Bias-voltage-dependent measurement of apparent barrier height on low-work-function thin film

Using a scanning tunneling microscope, we have examined the effect of the bias voltage on the apparent barrier height. The sample used in this study was a nitrogen-doped lanthanum hexaboride film. We experimentally proved that a linear relationship exists between the apparent barrier height and the sample bias voltage. As a consequence, we estimated the work function of the film to be 2.35 eV by theoretical fitting. This value is in good agreement with that obtained by photoemission spectroscopy in a previous study. Our results demonstrate that the work function calculated through apparent barrier height measurements is guaranteed to be highly reliable in spite of the simple one-dimensional model. We anticipate that the sensitivity of the barrier height to the sample work function can be utilized for elemental identification on surfaces with characteristic work functions.

Graphene as a Schottky Barrier Contact to AlGaN/GaN Heterostructures.

Electrical and noise properties of graphene contacts to AlGaN/GaN heterostructures were studied experimentally. It was found that graphene on AlGaN forms a high-quality Schottky barrier with the barrier height dependent on the bias. The apparent barrier heights for this kind of Schottky diode were found to be relatively high, varying within the range of φb = (1.0–1.26) eV. AlGaN/GaN fin-shaped field-effect transistors (finFETs) with a graphene gate were fabricated and studied. These devices demonstrated ~8 order of magnitude on/off ratio, subthreshold slope of ~1.3, and low subthreshold current in the sub-picoamperes range. The effective trap density responsible for the 1/f low-frequency noise was found within the range of (1–5) · 1019 eV−1 cm−3. These values are of the same order of magnitude as reported earlier and in AlGaN/GaN transistors with Ni/Au Schottky gate studied as a reference in the current study. A good quality of graphene/AlGaN Schottky barrier diodes and AlGaN/GaN transistors opens the way for transparent GaN-based electronics and GaN-based devices exploring vertical electron transport in graphene.

Piezotronic AlGaN nanowire Schottky junctions grown on a metal substrate

The non-centrosymmetric crystal structures of polar-semiconductors comprising GaN, InN, AlN, and ZnO intrigued the scientific community in investigating their potential for a strain-induced nano-energy generation. The coupled semiconducting and piezoelectric properties produce a piezo-potential that modulates the charge transport across their heterostructure interfaces. By using conductive-atomic force microscopy, we investigate the mechanism that gives rise to the piezotronic effect in AlGaN nanowires (NWs) grown on a molybdenum (Mo) substrate. By applying external bias and force on the NWs/Mo structure using a Pt–Ir probe, the charge transport across the two adjoining Schottky junctions is modulated due to the change in the apparent Schottky barrier heights (SBHs) that result from the strain-induced piezo-potential. We measured an increase in the SBH of 98.12 meV with respect to the background force, which corresponds to an SBH variation ∂ϕ∂F of 6.24 meV/nN for the semiconductor/Ti/Mo interface. The SBH modulation, which is responsible for the piezotronic effect, is further studied by measuring the temperature-dependent I–V curves from room temperature to 398 K. The insights gained from the unique structure of AlGaN NWs/Mo shed light on the electronic properties of the metal-semiconductor interfaces, as well as on the potential application of AlGaN NW piezoelectric nanomaterials in optoelectronics, sensors, and energy generation applications.

Elucidation of Inhomogeneous Heterojunction Performance of Al/Cu5FeS4 Schottky Diode With a Gaussian Distribution of Barrier Heights

Here, we analyze inhomogeneities in the barrier height (BH) of Al/Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> FeS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> Schottky device from the electrical (I-V) measurements with a temperature range between 303 and 408 K. The temperature-dependent performance of our fabricated device is analyzed by using the thermionic emission (TE) theory. Some important diode parameters like BH (Φ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">bo</sub> ), ideality factor (η), and series resistance (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</sub> ) are evaluated from the forward current-voltage characteristic curves. The calculated η and R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</sub> of the Schottky barrier diode (SBD) decrease, whereas the Φ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">bo</sub> of the device increases with the increase in temperature. The value of Richardson constant (A*) for our material is obtained as 1.94×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> A cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> in the temperature range 303-408 K, which is found as much lesser than the theoretical value of 29.90 A cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> . The discrepancy of A* from the theoretical value has been well explained by TE theory with the assumption of Gaussian distribution (GD) of BHs due to the existence of BH inhomogeneities at metal semiconductor (MS) junction. The obtained values of the mean BH Φ̅ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b̅o̅</sub> and the standard deviation σ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> are 1.026 eV and 173 mV in the corresponding temperature range. The mean BH (1.199 eV) and Richardson constant (29.73 Acm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> ) are determined from the modified Richardson plot depending on the inhomogeneity of BHs. Apparent BH consists of mean BH (Φ̅ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b̅o̅</sub> ) and standard deviation (σ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> ). The σ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> contributes significantly to the modification of Richardson constant and mean BH. The calculated value of the modified Richardson constant is in close agreement with the theoretical value. From C-V measurements built-in voltage and effective BH of this structure were calculated as a function of frequency.

Conductance Deep-Level Transient Spectroscopy and Current Transport Mechanisms in Au|Pt|n-GaN Schottky Barrier Diodes

The current transport mechanisms in Au|Pt|n-GaN Schottky barrier diodes are investigated in a temperature range of 40–325 K. The calculated barrier height and ideality factor are 1.12 and 2.13 eV, respectively, and it is observed that the barrier height Φb increases and the ideality factor n decreases with temperature increase. The apparent barrier height and the ideality factor derived by using thermionic emission theory are found to be strongly temperature-dependent. The increase in barrier height with increasing temperature has been explained as an effect of barrier inhomogeneity. This behavior has been interpreted based on the assumption of a Gaussian distribution of barrier heights due to barrier height inhomogeneity at the interface between the metal and semiconductor. The abnormal behavior of all these parameters can be attributed to the presence of deep levels thermally activated. Conductance deep-level transient spectroscopy (CDLTS) results shows that the two deep-level defects are observed in as-grown sample with activation energies of E1 = 0.18 eV and HL1 = 0.87 eV.

Co/aniline blue/silicon sandwich hybrid heterojunction for photodiode and low-temperature applications

The temperature dependence of the current–voltage and room temperature capacitance–voltage measurements of Co/aniline blue/ n-Si sandwich-type rectifying device was investigated.Furthermore, the effects of the illumination on the current–voltage measurements were tested with 100 mW/cm2 light intensity, and it was seen that Co/aniline blue/ n-Si sandwich-type device showed a clear response to illumination, and it may be a candidate for solar cells or photodiode applications. The rectifying device parameters, such as the barrier height (Ф), the ideality factor ( n), the rectification ratio, and the series resistance ( Rs), were obtained as a function of temperature using thermionic emission, Cheung function, and Norde function. The interface state densities versus energy were obtained. The Richardson constant ( A*) obtained from the In( Io/ T2) versus 1000/ T plot was much less than the theoretical value for n-Si. The mean Schottky barrier height[Formula: see text] and the standard deviation ( σo) were calculated using the apparent Schottky barrier height Фap versus 1/2 kT plot. So, it has been found to be 1.08 eV and 0.15 V (260–460 K) and 0.79 eV and 0.10 V (100–260 K), respectively. The results were discussed based on the presence of two Gaussian distributions of Фb potential in the contact area of Co/aniline blue/ n-Si/Al device.

High sensitive gas sensor based on vertical graphene field effect transistor

A gas sensor made from graphene vertical field effect transistor (VGr-FET) has been fabricated using graphene as the source electrode, C60 thin film as the semiconductor layer and aluminum thin film as the drain electrode. The on/off ratio of transistor gated by bottom electrode with ionic liquid gel as dielectric layer is derived to be 103 from measured source–drain current Ids. The apparent energy barrier height between the graphene and polycrystalline fullerene was calculated from the model of heterojunction diode I–V response curves. The barrier height φBH was altered by the gating potential vertically applied on graphene sheet, resulting the large on/off ratio of the transistor. The effect of surface adsorption of water vapor, oxygen, ammonia and isoprene gas phase molecules on the Ids was measured. The lower limit of detection (LOD) for ammonia (86 ppb) than that of isoprene (420 ppb) is attributed to the donor nature of ammonia contact with p-type graphene, and the adsorbed donor leads to a corresponding positive gating effect to the VGr-FET. This facile, low cost and quick responsive device shows promise for early diagnose of severe human respiratory diseases.

Effect of MoS2 film on memristor characteristics of ZnO film

Memory resistive devices using a ZnO dielectric layer are promising due to the transparent nature, lower operating voltage, synthesis compatible with semiconductor processing, and ability to control using magnetic fields. In the present work, niobium incorporated MoS2 films in combination with ZnO are used to form diode-resistor devices with memory. The two device structures p-Si-SiO2/Pt/MoS2(Nb)/ZnO/Ag and p-Si-SiO2/Pt/ZnO/Ag are grown using laser physical vapor deposition. The resistive characteristics are investigated as a function of temperature for comparison. The unipolar I-V characteristics of Pt/ZnO/Ag device films were found to be nonreproducible, and the temperature dependence was irregular for negative polarity. The unipolar I-V characteristics of Pt/MoS2(Nb)/ZnO/Ag device films were found to be reproducible. The temperature dependence of the I-V characteristics was regular for both polarities. The presence of a MoS2 film is found to improve and distinguish the effect of the polarity of the applied field on the unipolar device characteristics by the formation of a p-n device configuration. The conductance in the transition from a low resistance state to a high resistance state was found to follow the Schottky emission with the apparent barrier height being influenced by the p-n junction.

Temperature Dependent Current-Voltage Characteristics of Pt/MoS2 Schottky Junction

AbstractMolybdenum disulphide (MoS2) is one of the transition metal dichalcogenide (TMD) materials which has attracted attention due to its various interesting properties. MoS2 is very promising for electronic and optoelectronic devices due to its indirect band gap (∼1.2 eV) for few layer and direct band gap (∼1.8 eV) for monolayer MoS2. In MoS2 based Schottky devices, Schottky barrier height depends on the thickness of MoS2 because of its tunable electronic properties. Here, we have used DC sputtering technique to fabricate metal-semiconductor junction of MoS2 with platinum (Pt) metal contacts. In this work, MoS2 thin film (∼10 nm) was deposited on p-Silicon (111) using DC sputtering technique at optimized parameters. Schottky metallization of Pt metal (contact area ∼ 0.785x10-2 cm2) was also done using DC sputtering. Current-voltage (I-V) characteristics of the Pt/MoS2 Schottky junction have been investigated in the temperature range 80-350K. Forward I-V characteristics of Pt/MoS2 junction are analysed to calculate different Schottky parameters. Schottky barrier height increases and ideality factor decreases on increasing the temperature from 80-350K. The I-V-T measurements suggest the presence of local inhomogeneities at the Pt/MoS2 junction. Schottky barrier inhomogeneities occur in case of rough interface. In such cases, the Schottky barrier height does not remain constant and vary locally. Current transport through the Schottky junction is a thermally activated process. As temperature increases, more and more electrons overcome the spatially inhomogeneous barrier height. As a result, the ideality factor becomes close to unity and apparent barrier height increases due to increase in temperature.

Characterization of electrical transport and properties of an Al/porous Si (PS)/p-Si/Al heterojunction

In this paper is discussed the current transport characteristics of an Al/PS/p-Si/Al heterojunction device with a porous silicon layer (PS) fabricated by the electrochemical anodization process and its current transport properties are investigated by the using temperature dependent current-voltage (I-V) measurements in a wide temperature range from 50 K to 300 K. The electrical parameters are characterized with the thermionic emission theory. It is observed that the main characteristics such as ideality factor and apparent barrier height demonstrate resolute temperature dependences and this situation is related to the structure of porous region. In addition, it is obtained the conductance curves for the forward and reverse bias values of Al/PS/p-Si/Al sample and as a result, the value of the relative dielectric constant εr of porous layer is calculated as εr:3.72. From the reverse bias I-V curves, it is discussed the current conduction mechanism of porosity region by using Poole-Frenkel emission and Schottky emission. In result, it is commented that the charge transport in PS is through Poole-Frenkel conduction mechanism for Al/PS/p-Si/Al.