Gaussian Height Distribution Research Articles

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.

Fractional Brownian motion as a rough surface

In this study we consider two dimensional fractional Brownian motion (fBM) as a rough surface, tuned by the Hurst exponent H, with a focus on the scaling relations. While this system fulfills partially the requirements for self-similar Gaussian surfaces, (like Gaussian height distribution), it shows deviations for the global features. A thorough examination of the Kondev’s hyperscaling relations is presented. The global features associated with level lines which define contour loop ensemble (CLE) are studied in terms of H. We show that in the thermodynamic limit the fractal dimension of loops (Df), the critical exponent of the distribution of loop length (τl), and the gyration radius (τr) vary linearly with H. The hyperscaling relations between these quantities however challenge this hypothesis. While Df, τl and τr fulfill partially the Kondev relations, the loop correlation exponent xl depends weakly on H, i.e. shows deviations from 12 which is hypothesized by Kondev to be super-universal for the Gaussian surfaces.

Analysis of temperature-dependent current–voltage characteristics of Schottky diodes by the modified thermionic emission current model

We have investigated the behavior of current flow across an inhomogeneous Schottky diode (SD) as a function of temperature by numerical simulation. We have used the modified thermionic emission (TE) current expression with a Gaussian distribution of potential barrier heights. This modified TE model assumes the presence of a series of low-barrier patches at the Schottky contact and semiconductor interface. First, we have discussed the behavior of the patch current compound relative to the TE compound in the inhomogeneous SD at 300, 200, and 100 K, as a function of standard deviation and the number of circular patches N. Then, we have investigated the behavior of temperature- and bias-dependent and bias-independent current vs voltage (I–V–T) characteristics in the 75–300 K range. In bias-dependent I–V–T curves obtained for σ1=4.35×10−5cm2/3V1/3 and σ2=7.35×10−5cm2/3V1/3 at N1=1.81×106 or N2=1.81×108, an intersection behavior has been observed in the I–V curve at 75 K for σ2 at both N values; however, the same behavior has been not observed for σ1 at both N values due to σ1<σ2. That is, the current for σ2 at 75 K has exceeded the current at higher temperatures. This behavior has been ascribed to the effective BH to decrease with decreasing temperature value. In the I–V–T curves independent of bias, such an intersection has not been observed for σ1 while it has been observed for σ2 in the I–V curves at both 75 and 100 K. Thus, it has been concluded that the bias-dependeσnt I–V equations must be used to avoid this intersection behavior while fitting the experimental I–V curve of an SD to the theoretical I–V curve.

Analysis of barrier inhomogeneities in Ti/p–type strained Si0.95Ge0.05 Schottky diodes using reverse current-voltage characteristics

Extracting electrical parameters such as barrier height inhomogeneities (BHi) from the forward bias can be very challenging in metal/semiconductor (M/Sc) contacts characterized by low barrier height and high series resistance. In this work we demonstrate that the reverse bias characteristics can be used as an efficient alternative method to investigate the inhomogeneity of low barrier height in M/Sc contacts. In particular, the BHi in Ti/p-strained Si0.95Ge0.05 Schottky barrier diodes (SBD) has been investigated using reverse current–voltage-temperature (IR-VR-T) characteristics over the temperature range of 100–300 K. The temperature dependence of the measured barrier heights (ΦRBp) using reverse-bias is successfully explained in terms of a thermionic emission (TE) current transport associated with Gaussian distribution of the barrier height due BHi. The mean homogeneous barrier height (Ф‾RBp) and its corresponding standard deviation (σRs) were determined for different reverse voltages. A decrease in Ф‾RBp and an increase in σRs with increasing reverse bias are observed, indicating a large barrier height distribution upon high applied reverse bias. The deduced average zero-field barrier height (ФFBp≈0.59eV) from IR-VR agrees well with the corresponding value determined from the forward characteristics. Moreover, the reverse bias extracted values for Richardson constant A* based on BHi model, are found in fair agreement with the reported theoretical value of 32 A cm−2 K−2 for our p-type strained Si0.95Ge0.05 alloy. Finally, the results obtained on Pd/n-type Si0.90Ge0.10 structure shown in this work fully support the utilization of such reverse bias method.

InGaN based Schottky barrier solar cell: Study of the temperature dependence of electrical characteristics

The indium gallium nitride (InGaN) semiconductor alloy shows great promise for high-efficiency thin-film solar cells due to its intrinsic characteristics. However, there are major challenges in the development of high-quality p-doped and indium-rich InGaN layers to fabricate a pn or pin solar cell. This study focuses on the development of an alternative structure, not requiring p-doping, with a Schottky contact on n-type InGaN. The InGaN absorber was grown by metalorganic chemical vapor deposition and its structural, morphological and optical properties studied. Structural analysis by X-ray diffraction showed the growth of single crystal layers without phase separation. Indium compositions which vary up to around 8.3 % were confirmed by transmission measurements. The formation of V-shaped pits was observed with increased indium composition at lower growth temperatures. Schottky diodes based on InGaN with platinum metallic contacts were fabricated and their current–voltage characteristics studied in detail as a function of temperature. This analysis of the conduction mechanisms in Schottky/InGaN devices permitted in particular the extraction of the diode parameters as a function of the temperature showing a high rectification with an ideality factor of 1.15 with reverse saturation current of 6.7×10−9A at room temperature for an indium composition of 5.52 %. In addition, the analysis revealed the presence of a dual Gaussian distribution of barrier heights in a specific temperature range. Finally, the incident photon-to-electron conversion efficiency (IPCE) of the fabricated InGaN Schottky solar cells, measured using intensity-modulated photocurrent spectroscopy, reached a peak value of 51 %, which is among the highest published values for InGaN based solar cells.

Barrier Height, Ideality Factor and Role of Inhomogeneities at the AlGaN/GaN Interface in GaN Nanowire Wrap-Gate Transistor.

It is essential to understand the barrier height, ideality factor, and role of inhomogeneities at the metal/semiconductor interfaces in nanowires for the development of next generation nanoscale devices. Here, we investigate the drain current (Ids)-gate voltage (Vgs) characteristics of GaN nanowire wrap-gate transistors (WGTs) for various gate potentials in the wide temperature range of 130-310 K. An anomalous reduction in the experimental barrier height and rise in the ideality factor with reducing the temperature have been perceived. It is noteworthy that the variations in barrier height and ideality factor are attributed to the spatial barrier inhomogeneities at the AlGaN/GaN interface in the GaN nanowire WGTs by assuming a double Gaussian distribution of barrier heights at 310-190 K (distribution 1) and 190-130 K (distribution 2). The standard deviation for distribution 2 is lower than that of distribution 1, which suggests that distribution 2 reflects more homogeneity at the AlGaN/GaN interface in the transistor's source/drain regions than distribution 1.

Reynolds Number Dependency of Wall-Bounded Turbulence Over a Surface Partially Covered by Barnacle Clusters

The settlement of barnacles on a ship hull is a common form of marine biofouling. In this study, the Reynolds number dependency of turbulent flow over a surface partially covered by barnacle clusters is investigated using direct numerical simulations of turbulent channel flow at friction Reynolds numbers ranging from 180 to 720. Mean flow, Reynolds and dispersive stress statistics are evaluated and compared to the corresponding results for a generic irregular rough surface with a Gaussian height distribution. For the barnacle surface, distinctive features emerge in the velocity statistics due to the interplay between the barnacle clusters and the large, connected smooth-wall sections surrounding them. This aspect is further investigated by applying a rough-smooth decomposition to the local time-averaged flow statistics for the barnacle surface. Using this decomposition, the partial recovery of smooth-wall behaviour over the smooth sections of the barnacle surface can be observed in the Reynolds stress statistics with the streamwise Reynolds stresses exhibiting a similar behaviour as previously found for boundary layers over surfaces with a rough to smooth transition.

Diode paremeters extraction and study of space charge limited current in (Ag, Au)/CoS2 Schottky diodes

We investigated the electron transport properties of cobalt sulphide Schottky diodes with Au and Ag metal contacts. Pure CoS2 nanoplates were synthesized using solid state reaction method. From temperature dependent IV characterstics diode parameters including ideality factor, barrier height and Richardson cofficient were calculated for Au/CoS2 and Ag/CoS2 diodes. The value of barrier height increased with increasing temperature for both devices, however Ideality factor showed different trend. The values of modified Richardson coefficient by assuming the Gaussian distribution of the barrier heights turns out to be 244.20Acm−2K−2 and 348.20Acm−2K−2 for Au/CoS2 and Ag/CoS2 diodes respectively. At high voltages we observed Space Charge Limited Current (SCLC) with an exponential trap distribution in Au/CoS2 diode. The density of the traps and characteristic temperature associated with these traps were determine to be 2.47×1014cm−3 and 141 K, respectively.

Investigation of temperature dependant current transport mechanism in Ag/In2O3/p-Si/Al heterojunction

Employing the pulsed laser ablation technique nano-crystalline thin films of Indium oxide (In2O3) are deposited successfully on boron doped silicon substrate. The structural and morphological parameters of the films are investigated by using X-ray diffraction and atomic force microscopic (AFM) spectroscopy, respectively. The deposited films are the crystalline nanostructures with (400) as preferred diffraction peak and grain size of 56.56 nm approximately. The computed roughness (Rq) of In2O3 film is 1.02 nm. The AFM analysis validated the deposition of homogeneous smooth In2O3 films with surface roughness of the order of nanometer. UV–vis spectroscopy was used to study the optical properties of the films. Greater than 80% transparency in visible region was exhibited by the films. The value of the optical band gap was found to be 3.89 eV. The electrical parameters dominating the mechanism of current transport in n-In2O3/p-Si heterojunction were explored by observing the temperature-dependent current–voltage (I–V) properties. In the temperature range of 80–300 K, the ideality factor and barrier height were found to be strongly temperature dependent. It was noticed that with the decrease in temperature there is increase in ideality factor whereas decrease in barrier height which confirm the interfacial imperfections and inhomogeniety in potential barrier height distributions. The temperature dependence of I–V data has revealed the existence of double Gaussian distribution of barrier heights with mean values of 0.85eV and 0.78eV with standard deviation of 0.014 V and 0.012 V respectively. The modified Richardson's plot gives the average barrier height and Richardson's coefficient as 0.86eV and 4.7 × 105 Am−2K−2 in the temperature range 300 K–180 K and 0.77eV and 5.2 × 105 Am−2K−2, respectively in the temperature range 160 K–80 K. The values of Richardson's constants are of the order of known theoretical value of 3.2 × 105 Am−2 K−2.

4H-SiC Schottky barrier diodes as radiation detectors: A role of Schottky contact area

Large-area SiC Schottky barrier diodes can significantly improve the sensitivity in radiation detection due to the increased interacting SiC volume. In this work, we tested a large SiC detector with an area of 1 × 1 cm2. Extensive electrical characterization was performed at temperatures ranging from 150 K to 390 K, demonstrating the impact of barrier inhomogeneities on the electrical performance of the diode. Forward current-voltage (I-V) measurements of the diodes revealed two distinct regions caused by Schottky barrier inhomogeneity present throughout the entire temperature range. The barrier heights in the low- and high-current forward voltage regions were extracted from Richardson plots corrected for the Gaussian distribution of barrier heights, yielding values of 1.52 eV and 1.79 eV, respectively. Deep-level transient spectroscopy (DLTS) revealed only one deep-level defect, Z1/2, with an activation energy for electron emission of 0.67 eV, which was assigned to the known carbon vacancy. The DLTS study showed no correlation between electrically active defects and barrier inhomogeneity. An excellent energy resolution of 3.2 % was measured using a large area 241Am radiation source, consistent with values for small area SiC detectors that exhibited no barrier height inhomogeneities. The impact of temperature on the alpha particle radiation response was determined within a temperature range of 200 K to 390 K.

Implementation of Digital Image processing in Calculating Normal Approach for Spherical Indenter Considering Elastic/Plastic Contact

In this work a study and calculation of the normal approach between two bodies,spherical and rough flat surface, had been conducted by the aid of image processingtechnique. Four kinds of metals of different work hardening index had been used as asurface specimens and by capturing images of resolution of 0.006565 mm/pixel a good estimate of the normal approach may be obtained the compression tests had been done in strength of material laboratory in mechanical engineering department, a Monsanto tensometer had been used to conduct the indentation tests. A light section measuring equipment microscope BK 70x50 was used to calculate the surface parameters of the texture profile like standard deviation of asperity peak heights, centre line average, asperity density and the radius of asperities. A Gaussian distribution of asperity peak height was assumed in calculating the theoretical value of the normal approach in the elastic and plastic regions and where compared with those obtained experimentally to verify the obtained results.

Simulation of a Radio Signal Scattered from a Rough Surface by the Method of Stationary Points

Introduction. Many radar and radio navigation problems require adequate (i.e., corresponding to the physics of radio wave scattering under a certain set of conditions) simulation of a radio signal scattered from a rough surface. At present, four categories of mathematical models are used for these purposes, with each corresponding to a particular group of methods for solving the scattering problem. These methods include those based on a rigorous solution of the electrodynamic equations (methods of moments, finite elements, finite differences); approximate methods for solving electrodynamic problems (methods of small perturbations, tangent plane (Kirchhoff method), two-scale model); those of statistical equivalents; and phenomenological models. In the former two categories, the electromagnetic field is computed on a surface grid, whose step must be much smaller than the signal wavelength. This makes the simulation of a scattered radio signal effectively unrealizable for two-dimensional rough surfaces. The method of statistical equivalents is based on the calculation of the probabilistic characteristics of a scattered signal. Difficulties arising in this case narrow the possibilities of simulation, largely due to the impossibility of obtaining closed expressions for the required characteristics without significant simplifications. In addition, carrying out analytical calculations, the solution is restricted to the class of surfaces with the Gaussian distribution of roughness heights. Phenomenological models, although providing for a qualitative analysis of signal scattering from a rough surface, fail to take the physics of the scattering process into account.Aim. To create a simple and adequate model of a signal scattered from a two-dimensional rough surface using the tangent plane approximation of the boundary conditions (the Kirchhoff method), which can be realized on modern computers.Materials and methods. The proposed model of the scattered signal is based on its representation as a sum of signals reflected from stationary points on the surface, i.e., those points where the law of specular reflection of the incident electromagnetic wave is locally fulfilled.Results. The implementation of the model is reduced to determination of the positions of stationary points on a twodimensional rough surface. This problem is solved on modern computers quite simply without computations with complex numbers. It turns out that the number of stationary points, even with a large surface roughness, rarely exceeds two. This fact, along with the simplicity of finding the coordinates of stationary points, makes this model suitable for long series of statistical runs.Conclusion. The proposed model is easy to implement and can be used to study the accuracy of low-altitude target estimation, altimeters, Doppler and correlation speed and drift angle estimators.

Temperature-dependent Schottky diode behavior of Ni Schottky contacts to α-Ga2O3 film epitaxially grown on sapphire substrate

We fabricated Ni Schottky contacts on α-Ga2O3 epitaxial layers grown on a c-plane sapphire substrate and explored their current–voltage (I–V) characteristics dependence on temperature spanning over a wide temperature range of 100–425K. The Ni/α-Ga2O3 Schottky diode displayed excellent rectification, exhibiting a high barrier height of 1.39 eV, a low leakage current of the order 10−12 A, and a breakdown voltage of 215 V at room temperature. The reverse leakage current was confined within an order of magnitude over the entire measured temperature range, indicating the thermal stability of the diode. A large ideality factor of 1.20 attained at room temperature clearly indicates the diode behavior deviation from the ideal thermionic emission theory. The I–V characteristics revealed that the barrier height and ideality factor shows strong temperature dependence, indicating the existence of barrier inhomogeneity at the Schottky interface. An analysis of the barrier inhomogeneity using the thermionic emission with the assumption of a Gaussian barrier height distribution implies the prevailing double Gaussian barrier height distribution in the Ni/α-Ga2O3 Schottky diode with a transition at 250 K. The Richardson constant derived from the modified Richardson plot, evaluated by assuming the barrier height Gaussian distribution, was close to the theoretical Richardson constant of α-Ga2O3.

Capabilities and limits of surface roughness measurements with monochromatic speckles.

For coherent light illumination, surface roughness leads to speckles in the scattered light image. By evaluating the speckle contrast or image auto-correlation, a measurement of the roughness parameter S q is possible. While these measurement principles have been well known for decades, a fundamental understanding of the minimal achievable measurement uncertainty is missing. Therefore, the measurement uncertainty limits for four unavoidable sources of uncertainty are derived by means of theoretical and numerical approaches. The study is focused on the case of monochromatic speckles, which provide the highest sensitivity, as well as on the case of planar surface and isotropic surface roughness with a Gaussian height distribution and Gaussian correlation function. The considered uncertainty sources are the natural randomness of surface roughness itself, speckle noise, quantum shot noise, and camera noise. As a result, for the studied experimental configuration, speckle noise is determined as the largest contribution to measurement uncertainty, which leads to a minimal achievable relative uncertainty of 1%-2% for S q =(0.03-0.15)λ. According to theoretical studies, the speckle noise limit of the relative uncertainty is inversely proportional to four times the square root of the independent number of evaluated speckles. In addition, an absolute uncertainty limit is reached for ever-smoother surfaces, which amounts to λ divided by 64 times the square root of the independent number of evaluated speckles. Furthermore, systematic errors due to cross-sensitivity with respect to other parameters of surface roughness (height distribution, correlation length) as well as the surface position and shape (axial offset, tilt, curvature) are quantified and discussed. For the considered small deviations of different influencing quantities, the quantified errors are one order of magnitude smaller than the speckle noise limit.

Modeling frictional precursory phenomena using a wear-based rate- and state-dependent friction model in the laboratory

We examine numerical models that employ the rate-and-state frictional (RSF) framework to investigate earthquake sequences using laboratory driven descriptions of heterogeneous frictional properties. Using previously obtained experimental measurement of roughness, we observed that wear produced a bimodal Gaussian distribution of surface heights, which we hypothesized produced spatial heterogeneity of the critical slip distance Dc. In this numerical study, the fault surface was binarized into discrete smooth or rough sections, producing a barcode style version of frictional heterogeneity. The fault was predominantly rough except for two dominant asperities (A1 and A2) representative of larger polished sections. We simulated the resistive effect of increasing the fracture energy (toughness) of the rough barriers while maintaining constant properties of the embedded brittle/smooth asperities. Our numerical simulations generated burst-like seismic events and aseismic transients throughout the interseismic phase. At the late interseismic phase, bursts of seismicity (foreshocks) interacted with the accelerating preslip region at the transition to the preseismic (nucleation) phase. At lower levels of toughness heterogeneity, the slip rate increase was roughly inversely proportional to the time-to-failure tf for larger events. As fault toughness was increased, the dominant asperities initiated nucleation and thus force deviations of the fault from the smooth 1/tf acceleration observed for the homogeneous case, producing a rate-dependent cascade response. The calculations were validated by comparing two independently measured metrics from the experiments: (1) The expansion rate of slow ruptures during the interseismic and preslip phase and (2) the scalar seismic moment and source dimensions. While our study does not address the scaling problem, these results help to understand laboratory experiments that investigate transition to the preseismic (nucleation) phase during complex earthquake sequences.

Inhomogeneous heterojunction performance of Zr/diamond Schottky diode with Gaussian distribution of barrier heights for high sensitivity temperature sensor

Herein, we demonstrated the fabrication and operation of vertical diamond Schottky barrier diode (SBD) as a high-performance temperature sensor. The current transport mechanism and temperature sensor properties of Zr/p-diamond SBD were comprehensively investigated with operating temperatures up to 448 K. At room temperature, Zr/p-diamond SBD exhibits outstanding performances with a high rectification ratio of 2.28 × 1010, a low specific on-resistance of 0.5 mΩ•cm2, a large Schottky barrier height (SBH) of 1.43 eV, a low ideality factor of 1.77, and an extremely low saturation current of 4.42 × 10−22 A. The enhanced-performance with a higher forward current and a lower reverse leakage current is observed to be across a wide temperature range from 323 to 448 K. Additionally, a significant improvement of rectifying current curve with a highest rectification ratio over 1012 is obtained at 423 K. The SBH increases whereas the ideality factor decreases with temperature increasing, indicating barrier inhomogeneities at Zr/p-diamond interface. The temperature-dependent electrical transport characteristics on spatially inhomogeneous Schottky contacts can be successfully described by potential fluctuations model. The extracted original value of Richardson constant (A*) is 0.0153 A/cm2•K2, which is much lesser than theoretical value of 96 A/cm2•K2. The discrepancy of A* value from theoretical value has been well explained by thermionic emission model with Gaussian distribution of barrier inhomogeneity. The values of mean SBH and A* extracted from modified Richardson plot depending on SBH inhomogeneity are 1.76 eV and 105.51 A/cm2•K2, respectively. With a Gaussian distribution take into account, the A* value is close to the theoretical value, and confirmed the existence of SBH inhomogeneity at Zr/p-diamond interface. Furthermore, for Zr/p-diamond SBD operating as a temperature sensor, the voltage drop across the diode decreases linearly with increasing temperature at a specific forward current level, contributing to a highest sensor sensitivity of 6.8 mV/K. The reported results in this work are among the best to date in diamond SBD temperature sensor. Although not optimized for temperature sensor, the high and thermally stable rectifying barriers make Zr/p-diamond SBD a strong candidates for high-performance diamond rectifying diode and temperature sensor.

Heavy-ion fusion reactions of astrophysical interest

The hindrance in fusion of heavy-ion reactions crops up in the region of extreme sub-barrier energies. This phenomenon can be effectively analyzed using a simple diffused barrier formula derived assuming a Gaussian distribution of fusion barrier heights. Folding the Gaussian barrier distribution with the classical expression for the fusion cross section for a fixed barrier, the fusion cross section is obtained. The energy dependence of the fusion cross section provides good description to the existing data on sub-barrier heavy-ion fusion for lighter systems of astrophysical interest. Using this simple formula, an analysis has been presented from $^{16}$O + $^{18}$O to $^{12}$C + $^{198}$Pt, all of which were measured down to $<$ 10 $\mu$b. The agreement of the present analysis with the measured values is better than those calculated even from the sophisticated coupled channels calculations. The relatively smooth variation of the three parameters of this formula implies that it may be exploited to estimate the excitation function or to extrapolate cross sections for pairs of interacting nuclei which are yet to be measured. Possible extensions of the present methodology and its limitations have also been discussed.

Findings of inhomogeneity in barrier height of Schottky junction Al/rGO-SnO2 having anomaly in theoretical and experimental value of Richardson constant: A Gaussian approach

In this research, the temperature dependent dynamical behavior of Schottky junction Al/rGO-SnO2 has been investigated with thermionic emission (TE) theory within the temperature regime 303 K to 423 K at interval 20 K. During analysis of electrical charge transport behavior an anomalous change is observed in the value of ideality factor and barrier height with rising temperature for the junction. Experimentally derived Richardson constant (of the order 10-5A/m2K2) using TE theory is exceptionally substandard to the theoretical (of the order 106A/m2K2) values. The beauty of this work is to find out the underline physics for this discrepancy in measurement of Richardson constant (might arose due to inhomogeneity in barrier of metal-semiconductor junction) by assuming the Gaussian distribution of the barrier height with TE theory at the junction. It is obvious that the occurrence of barrier inhomogeneity across the junction leading charge transport phenomena which mostly impacting upon the parameters of Schottky diodes and its nature because of intrinsic formation of ripples and ridges. In this study, it is found that the charge transport mechanism is highly follows the single Gaussian distribution. The material characterization and its Schottky behavior in normal temperature had been published elsewhere.

Bistatic Radar Scattering from Non-Gaussian Height Distributed Rough Surfaces

In modeling a rough surface, it is common to assume a Gaussian height distribution. This hypothesis cannot describe an eventual asymmetry between crests and troughs of natural surfaces. We analyzed the bistatic scattering from a rough surface with non-Gaussian height distributions using the Kirchhoff scattering theory. Two extreme cases of Gamma-distributed surfaces were compared in particular: exponential and Gaussian distributions. The bistatic angular dependence was examined under various root mean square (RMS) heights and power spectrum densities. Contribution sources to the coherent and incoherent scattering components were singled out relating to the surface height distribution. For an exponential height surface, the coherent scattering strengthens even as the surface becomes rough. The non-Gaussian effect on the incoherent scattering is connected with surface power spectrum density. The height distribution impacts differ in the different regions of the bistatic scattering plane and thus complicate the differentiation of the scattering patterns due to height distribution.

Negative Schottky barrier height and surface inhomogeneity in n-silicon M–I–S structures

The alleviation effect on the Schottky barrier height (SBH) (ΦB) using ultrathin titanium dioxide and hafnium dioxide dielectrics in a single layer and a bilayer stack was demonstrated. ΦB in the Pt/n-Si contact was reduced from 0.53 to −0.058, 0.3, and −0.12 eV using 3 nm TiO2, 1 nm HfO2, and high-k/high-k bilayer insertion, respectively. A maximum of 122% reduction in ΦB was obtained using bilayer dielectric insertion, which is the highest ever reduction reported so far in a Schottky diode. This was achieved by effectively passivating the semiconductor surface states by HF cleaning followed by inserting an ultrathin film produced from the novel Atomic Layer Deposition (ALD) technique. The Gaussian distribution (GD) of barrier heights all over the interface has been investigated for both Metal–Semiconductor (M–S) and Metal–Insulator–Semiconductor (M–I–S) contacts. The nonlinear behavior in a conventional Richardson plot was observed with lower values of the Richardson constant (A*). We have reported the surface inhomogeneity in both M–S and M–I–S contacts through temperature dependency of diode characteristics. The standard deviation (σ) as evidence for the Gaussian distribution of barrier heights was determined using the ln(Is/T2) vs q/2kT plot. The results were validated by a modified Richardson plot where the values of A* obtained were found to be in close agreement with the known values. As the ALD technique is known for conformity and uniformity of thin films, the dielectric insertion has proved effective in mitigating the SBH. However, the inhomogeneity in both M–S and M–I–S points to the role of dipole formation at the interface.