Effective Richardson Constant Research Articles

Temperature dependence of electrical characteristics and interface state densities of Au/n-type Si structures with SnS doped PVC interface

In this study, the electrical properties of Au/(SnS doped PVC)/n–Si structures were investigated in detail using current/voltage (IV) data in wide temperature range (80–340 K by 20 K steps). Some of the basic electrical parameters such as ideality factor (n), saturation current (I 0), and barrier height (Φ bo ) were obtained. When these parameters were extracted using thermionic emission (TE) theory, it was found that the value of n decreases whereas Φ bo increases with increasing temperature. This result can be explained by the barrier height (BH) inhomogeneity. The observed two linear regions in the plots of Φ bo –n, Φ bo –(1/2kT)1 and (n −1–1)–(1/2kT) in temperature regions of 80–160 K and 80–340 K form an evidence to the presence of Double Gaussian distribution (DGD). Using the plot of Φ bo –(1/2kT), the values of mean BH () and standard deviation (σ S) were found as 0.486 eV and 66 mV for first region, and 0.984 eV and 139 mV for second region, respectively. Thus, the effective Richardson constant (A*) was obtained using the interception point of the modified Richardson plot for these regions as 7.013 × 10−6 A.K−2cm−2 and 88.12 A.K−2cm−2, respectively. It is clear that A* value for second region is closer to theoretical value (=112 A.K−2cm−2 for n–Si). Finally, the energy dependent profile of the surface-states (Nss) was extracted using Card-Rhoderick method and Nss was found to range from ∼1012 (at 80 K) to 1013 eV−1 cm−2 (at 340 K).

Evaluation of Richardson Constant of Fruit dyes using Carmoisine and Tartrazine

One of the most crucial variables to consider while analysing the current conduction process in the metal organic Schottky contact is the Richardson constant. However, there aren't many publications on the determination of the useful Richardson constant for Fruit dyes. For two different Fruit dyes, Carmoisine, and Tartrazine, we have determined the values of the effective Richardson constant in this work. By using the spin coating method, a thin organic layer of these natural colours was sandwiched between a copper plate and a piece of glass that had been coated in indium tin oxide. The current-voltage-temperature response of the cells was examined at a temperature range of 303K to 333K. The estimated effective Richardson constants for these dyes are 95.09 x 10-3 A/cm2K2 and 44.35 x 10-3 A/cm2K2 for CS and TZ dye respectively, which are different from the typical value of 120 A/cm2K2. We can analyse several electrical properties for these natural dyes with the aid of these values.

Non Ideal Schottky Barrier Diode’s Parameters Extraction and Materials Identification from Dark <i>I-V-T</i> Characteristics

Several parameters of a commercial Si-based Schottky barrier diode (SBD) with unknown metal material and semiconductor-type have been investigated in this work from dark forward and reverse I-V characteristics in the temperature (T) range of [274.5 K - 366.5 K]. Those parameters include the reverse saturation current (Is), the ideality factor (n), the series and the shunt resistances (Rs and Rsh), the effective and the zero bias barrier heights (ΦB and ΦB0), the product of the electrical active area (A) and the effective Richardson constant (A**), the built-in potential (Vbi), together with the semiconductor doping concentration (NA or ND). Some of them have been extracted by using two or three different methods. The main features of each approach have been clearly stated. From one parameter to another, results have been discussed in terms of structure performance, comparison on one another when extracted from different methods, accordance or discordance with data from other works, and parameter’s temperature or voltage dependence. A comparison of results on ΦB, ΦB0, n and NA or ND parameters with some available data in literature for the same parameters, has especially led to clear propositions on the identity of the analyzed SBD’s metal and semiconductor-type.

Graphene-Silicon Device for Visible and Infrared Photodetection.

The fabrication of a graphene–silicon (Gr-Si) junction involves the formation of a parallel metal–insulator–semiconductor (MIS) structure, which is often disregarded but plays an important role in the optoelectronic properties of the device. In this work, the transfer of graphene onto a patterned n-type Si substrate, covered by Si3N4, produces a Gr-Si device, in which the parallel MIS consists of a Gr-Si3N4-Si structure surrounding the Gr-Si junction. The Gr-Si device exhibits rectifying behavior with a rectification ratio up to 104. The investigation of its temperature behavior is necessary to accurately estimate the Schottky barrier height (SBH) at zero bias, φb0 = 0.24 eV, the effective Richardson’s constant, A* = 7 × 10–10 AK–2 cm–2, and the diode ideality factor n = 2.66 of the Gr-Si junction. The device is operated as a photodetector in both photocurrent and photovoltage mode in the visible and infrared (IR) spectral regions. A responsivity of up to 350 mA/W and an external quantum efficiency (EQE) of up to 75% are achieved in the 500–1200 nm wavelength range. Decreases in responsivity to 0.4 mA/W and EQE to 0.03% are observed above 1200 nm, which is in the IR region beyond the silicon optical band gap, in which photoexcitation is driven by graphene. Finally, a model based on two parallel and opposite diodes, one for the Gr-Si junction and the other for the Gr-Si3N4-Si MIS structure, is proposed to explain the electrical behavior of the Gr-Si device.

Estimation of Richardson Constant for Natural Organic dye Based Cells using Orange-lemon and Apple-green

The Richardson constant is one of the most important parameters to analyze the current conduction process in the metal organic Schottky contact. But there are very few reports available on the estimation of effective Richardson constant for the natural dyes. In this work, we have estimated the values of effective Richardson constant for two different natural dyes namely Orange-Lemon and Apple-Green. A thin organic film of these herbal dyes was sandwiched in between Indium Tin Oxide-coated glass and a Copper plate by spin coating technique. The current-voltage-temperature response of the cells was investigated at a temperature interval of 303K to 333K using Keithley 2400 source meter. The effective Richardson constants for these dyes have been estimated which are 110 x 10-3 A/cm2K2, and 118 x 10-3 A/cm2K2 for OL and AG dye respectively, which is different from the conventional value of 120 A/cm2K2. These values will help us to study different electrical parameters for these natural dyes.

Gaussian Thermionic Emission Model for Analysis of Au/MoS2 Schottky-Barrier Devices

Schottky-barrier inhomogeneities are expected at the metal--transition-metal-dichalcogenide (TMDC) interface and this can impact device performance. However, it is difficult to account for the distribution of interface inhomogeneity as most techniques average over the spot area of the analytical tool (e.g., few hundred micrometers squared for photoelectron-based techniques), or the entire device measured for electrical current-voltage (I-V) measurements. Commonly used models to extract Schottky-barrier heights neglect or fail to account for such inhomogeneities, which can lead to the extraction of incorrect Schottky-barrier heights and Richardson constants that are orders of magnitude away from theoretically expected values. Here, we show that a Gaussian-modified thermionic emission model gives the best fit to experimental temperature-dependent current-voltage (I-V-T) data of van der Waals $\mathrm{Au}$/p-${\mathrm{Mo}\mathrm{S}}_{2}$ interfaces and allow the deconvolution of the Schottky-barrier heights of the defective regions from the pristine region. By the inclusion of a Gaussian-distributed Schottky-barrier height in the macroscopic I-V-T analysis, we demonstrate that interface inhomogeneities due to defects are deconvoluted and well correlated to the impact on the device behavior across a wide temperature range from a room temperature of 300 K down to 120 K. We verify the Gaussian thermionic model across two different types of p-${\mathrm{Mo}\mathrm{S}}_{2}$ (geological bulk crystals and synthetic flux-grown crystals), and finally compare the macroscopic Schottky-barrier heights with the results of a nanoscopic technique, ballistic hole emission microscopy (BHEM). The results obtained using BHEM are consistent with the pristine $\mathrm{Au}$/p-${\mathrm{Mo}\mathrm{S}}_{2}$ Schottky-barrier height extracted from the Gaussian-modified thermionic emission model over hundreds of nanometers. Our findings show that the inclusion of Schottky-barrier inhomogeneities in the analysis of I-V-T data is useful to elucidate the impact of defects (e.g., grain boundaries, metallic impurities, etc.) and hence their influence on device behavior. We also find that the effective Richardson constant, a material-specific constant typically treated as merely a fitting constant, is a useful parameter to check for the validity of the transport model.

Investigation of electrical parameters of Au/P3HT:PCBM/n-6H–SiC/Ag Schottky barrier diode with different current conduction models

Abstract We have researched the electrical characteristics of Au/P3HT:PCBM/n-6H–SiC/Ag Schottky barrier diode (SBD) fabricated with a polymer interface layer between 300 and 375 K temperatures. The experimentally obtained parameters from current-voltage (I–V) measurements are calculated with four different current conduction models. It is observed that parameters calculated from research findings related to different methods are compatible with each other. The barrier inhomogeneity of the metal-polymer-semiconductor (MPS) interface layer is explained by Gaussian distribution (GD). Furthermore, the mean barrier height ( Ф ‾ bo) and the modified effective Richardson constant (A**) are found by drawing Richardson curves of the sample. Finally, the electrical properties of Au/P3HT:PCBM/n-6H–SiC/Ag SBD have been determined to affect the interface materials and the interface state density (Nss) as well as the current conduction models.

The investigation of temperature dependent electrical characteristics of Au/Ni/β-(InGa)2O3 Schottky diode

We have grown β-(In0.04Ga0.96)2O3 thin film by pulsed laser deposition(PLD) on Sn doped β-Ga2O3(-201) substrates and fabricated the Au/Ni/β-(InGa)2O3 Schottky diodes on it. The electrical characteristics of the diodes were investigated within the temperature range from 300K to 400K. Based on the theory of thermal electron emission (TE), the extracted barrier height ϕb and ideality factor n are strongly temperature dependent. ϕb increasing from 0.83 eV to 0.93 eV while n decreasing from 2.82 to 1.83, respectively. By taking the Gaussian distribution of the Schottky barrier height into account, the average barrier height was calculated to be 1.18 eV with a standard deviation of 0.135 V and the effective Richardson constant A* was also determined to be 42.34 Acm−2K−2.

Lanthanum (oxy)boride thin films for thermionic emission applications

The chemical-physical properties of thin lanthanum (oxy)boride films deposited on polycrystalline tantalum substrates by different deposition techniques (Pulsed Laser Deposition - PLD - with either nanosecond or femtosecond laser source, and electron beam evaporation) were compared in order to investigate the effect of chemical composition, crystallinity, surface morphology of the thin films on the thermionic electron emission capability. The emission performance of the films was analyzed in the 700–1600 °C temperature range, allowing the determination of work function values ranging from 2.59 to 2.85 eV and an effective Richardson constant at least one order of magnitude lower than the ideal value for all the films. The highest measured thermionic current density value of 1.68 A/cm2 at 1600 °C was provided by the samples grown by femtosecond PLD, indicating a promising performance for practical application in high-temperature thermal-to-electric energy conversion.

Analysis of current transport mechanisms in sol-gel grown Si/ZnO heterojunction diodes in high temperature environment

This paper analyzes the electrical parameters of Si/ZnO heterojunction diodes in the wide temperature range, i.e. from room temperature (298 K) to 573 K to study the electrical performance of the diode in very high temperature environment. In this work, sol-gel derived nanostructured ZnO thin film was deposited directly on p-Si substrate using spin coating technique. Electrical parameters, such as rectification ratio, reverse saturation current, ideality factor, barrier height, series resistance and activation energy are derived from current-voltage characteristics of the device, measured using semiconductor parameter analyzer in the temperature range of 298 K–573 K for bias voltage of ±5 V. The ideality factor, barrier height and series resistance is derived as 2.66, 0.789 eV and 3554 Ω respectively at 298 K, whereas at 573 K these are modified as 1.58, 1.15 eV and 801 Ω respectively. The above-mentioned results indicate the presence of spatial barrier height inhomogeneities (BHI) in high temperature environment. Hence, we have included the Gaussian distribution of spatial BHI in our analysis to calculate the effective Richardson constant (RC). Before inclusion of spatial BHI, RC was 4.026 × 10−6 Acm−2K−2. However, after inclusion of spatial BHI, RC is modified to 29.14 Acm−2K−2, which is nearer to the theoretical value (32 Acm−2K−2). Therefore, this study indicates that our as-fabricated Si/ZnO heterojunction diodes can sustain their electrical behaviour in very high temperature environment also and they are suitable for high temperature electronic and optoelectronic application.

Measure and analysis of 4H-SiC Schottky barrier height with Mo contacts

Current–voltage (I–V) and capacitance–voltage (C–V) characteristics of Schottky Mo/4H-SiC diodes have been measured and analyzed as a function of temperature between 80 and 400 K. The I–V characteristics significantly deviate from ideal characteristics predicted by the thermionic emission model because of the inhomogeneity of Schottky contact. After a brief review of the different existing models, the main parameters (ideality factor, barrier height, and effective Richardson constant) of both diodes have been extracted in the frame of a Gaussian barrier height distribution model, whose mean and standard deviation are linearly dependent on voltage and temperature, as well as in the context of the potential fluctuation model. The results are compared with the values extracted by C–V and the values in the literature. A link is established between these two models. Diodes of different I–V characteristics, either identified as single barrier or double barrier, have been analyzed by Deep Level Transient Spectroscopy (DLTS) to investigate the deep level defects present. No noticeable difference has been found.

Gaussian distribution in current-conduction mechanism of (Ni/Pt) Schottky contacts on wide bandgap AlInGaN quaternary alloy

The current-conduction mechanisms of the as-deposited and annealed at 450 °C (Ni/Pt) Schottky contacts on AlInGaN quaternary alloy have been investigated in the temperature range of 80–320 K. The zero-bias barrier height (BH) (ΦB0) and ideality factor (n) of them were evaluated using thermionic emission (TE) theory. The ΦB0 and n values calculated from the I-V characteristics show a strong temperature dependence. Such behavior of ΦB0 and n is attributed to Schottky barrier inhomogeneities. Therefore, both the ΦB0 vs n and ΦB0 vs q/2kT plots were drawn to obtain evidence on the Gaussian distribution (GD) of the barrier height at the metal/semiconductor interface. These plots show two different linear parts at low and intermediate temperatures for as-deposited and annealed Schottky contacts. Thus, the mean value of ΦB0 and standard deviation (σ0) was calculated from the linear parts of the ΦB0 vs q/kT plots for both samples. The values of the effective Richardson constant (A∗) and mean BH were obtained from the modified Richardson plots which included the effect of barrier inhomogeneity. These values of Richardson constant and barrier height for as-deposited contacts were found to be 19.9 A cm−2 K−2 and 0.59 eV, respectively, at low temperature, but 43.3 A cm−2 K−2 and 1.32 eV, respectively, at intermediate temperatures. These values of Richardson constant and barrier height for annealed contacts were found to be 19.6 A cm−2 K−2 and 0.37 eV, respectively, at low temperature, but 42.9 A cm−2 K−2 and 1.54 eV, respectively, at intermediate temperatures. It is clear that the value of the Richardson constant obtained for as-deposited and annealed samples by using double-GD for intermediate temperatures is close to the theoretical value of AlInGaN (=44.7 A cm−2 K−2). Therefore, I-V-T characteristics for the as-deposited and annealed Schottky contacts in the temperature range of 80–320 K can be successfully explained based on TE theory with double-GD of the BHs.

Current-Transport Mechanisms of the Al/(Bi2S3-PVA Nanocomposite)/p-Si Schottky Diodes in the Temperature Range Between 220 K and 380 K

In this research, bismuth sulfide nanostructures were prepared in the presence of polyvinyl alcohol (PVA) as a capping agent by an ultrasound-assisted method. The x-ray diffraction results show the crystalline phase of the sample and the mean crystalline size estimated by Debye–Scherer’s equation. The UV–Vis absorption spectrum show that the optical absorbance edge of Bi2S3 nanostructure was blue-shifted. The Fourier transform infrared spectra confirm the presence of PVA in the sample and transmission electron microscopy imaging shows that the structures are in nanoscale. The semi-logarithmic forward bias I–V plots have two distinct linear regimes for each temperature which are called low- and moderate-bias regions (LBR and MBR). In order to effectively interpret possible current-conduction/transport mechanisms, the reverse saturation current (Io), ideality factor (n) and zero-bias barrier height (ΦBO) were obtained from the slope and intercept of these plots and they were found to be a strong function of temperature and voltage. The high value of n even at high temperature and the increase of ΦBO with increasing temperature for the two regions is clear evidence of the deviation from thermionic emission (TE) theory. Therefore, ΦBO versus n and q/2kT plots were drawn to get evidence of the Gaussian distribution (GD) of the barrier height (BH) and they show a linear behavior. The mean values of BH ( $$ \bar{\Phi }_{\rm{BO}} $$ ) and standard deviation (σs) were also obtained from the intercepts and slopes of the ΦBO versus q/2kT plots as 1.44 eV and 0.19 V for the LBR and 1.32 eV and 0.18 V for the MBR, respectively. After that, the values $$ \bar{\Phi }_{\rm{BO}} $$ and effective Richardson constant (A*) were obtained as 1.29 eV and 267.6 A/(cm K)2 for the LBR and 1.27 eV and 281.7 A/(cm K)2 for the MBR, respectively. Such non-ideal I–V–T characteristics for the Al/(PVA-Bi2S3)/p-Si structure can be successfully explained by the single GD of BH for the LBR and MBR.

The investigation of current-conduction mechanisms (CCMs) in Au/ (0.07Zn-PVA)/n-4H-SiC (MPS) Schottky diodes (SDs) by using (I-V-T) measurements

The semi-logarithmic forward bias I-V plots of the Au/(0.07Zn-PVA)/n-4H-SiC (MPS) type SBDs showed double exponential behavior therefore these plots revealed two distinct linear regions which correspond to low (0.05 V ≤ 0.4 V) and moderate voltage regions (0.4 ≤ V ≤ 0.8 V) (LBR and MBR), respectively, for each temperature level. It was observed that the value of ideality factor (n) decreased with increasing temperature whereas opposite behavior occurred for zero-bias barrier height (ΦB0). The behavior of nkT/q vs kT/q plot for MBR indicated that a combination of thermionic field emission (TFE) and field emission (FE) mechanisms, i.e. the tunneling mechanism, may be dominant especially at low temperatures. In order to explain such unexpected behavior of the conduction mechanism; ΦB0 vs n, ΦB0 vs q/2kT and (n−1 − 1) vs q/2kT plots were drawn to obtain an evidence of a Gaussian distribution (GD) of the barrier heights (BHs) and all of them revealed two linear regions for both LBR and MBR. The conventional Richardson plot was modified by using the obtained standard deviation (σso) of BH from ΦB0 vs q/2kT plots for two bias regions. Thus, the mean BH (Φ̅B0) and effective Richardson constant (A*) values for LBR were calculated from the slope and intercept of the modified Richardson plots as 0.730 eV, 114.12 A cm−2 K−2 at low temperature range (100 ≤ T ≤ 200 K) and 1.304 eV, 97.33 A cm−2 K−2 at high temperature range (200 ≤ T ≤ 320 K), respectively. These values for MBR were found as 0.687 eV, 144.97 A cm−2 K−2 at low temperature range and 1.165 eV, 122.11 A cm−2 K−2 at high temperature range, respectively. It is clear that the values of A* for MBR at low temperatures are closer to 146 A cm−2 K−2 which represents the theoretical value of for n-4H-SiC. As a result, the current conduction mechanisms (CCM) in Au/(0.07Zn-PVA)/n-4H-SiC (MPS) SD can be successfully explained by thermionic emission (TE) mechanism with the double GD of BHs.

Dielectric properties, electrical modulus and current transport mechanisms of Au/ZnO/n-Si structures

Au/ZnO/n-Si (MIS) structures were fabricated by using the RF sputtering method and their complex dielectric constant (ε*=ε’-jε’’), electric modulus (M*=M′+ jM’’) and electrical conductivity (σ = σdc+σac) values were investigated as a function of frequency (0.7 kHz-1 MHz) and voltage (−6 – (+6 V)) by capacitance-voltage (C-V) and conductance-voltage (G/ω-V) measurements to get more information on the conduction mechanisms and formation of barrier height between Au and n-Si. The lnσ-Lnf plots have two different regions corresponding to low-intermediate and high frequencies. Such behavior of lnσ−lnf plots shows that the existence of two different conduction mechanisms (CMs) at low-intermediate and high frequencies. Moreover, the reverse bias saturation current (Io), ideality factor (n), barrier height (ΦBo) were determined from the forward bias I-V data and they were found as a strong function of temperature. The value of n especially at low temperature is considerably higher than unity. The values of Φ̅B0 and standard deviation(σs) were found from the intercept and slope of ΦBo-q/2kT plots as 0.551 eV and 0.075 V for the region I (80–220 K) and 1.126 eV and 0.053 V for the region II (220–400 K), respectively. The values of Φ̅Bo and effective Richardson constant (A*) were found from slope and intercept of activation energy plots as 0.564 eV and 101.084 Acm−2 K−2 for the region I and 1.136 eV and 41.87 Acm−2 K−2 for the region II, respectively. These results confirm that the current-voltage-temperature (I-V-T) characteristics of the fabricated Au/ZnO/n-Si SBDs can satisfactorily be explained on the basis of TE theory with double GD of the BHs.

Temperature effects on the electrical characteristics of $$\mathrm{Al}/\mathrm{PTh}-\mathrm{SiO}_{2}/\mathrm{p\hbox {-}Si}$$ Al / PTh - SiO 2 / p - Si structure

The temperature-dependent current–voltage (\(I\text {--}V\)) and capacitance–voltage (\(C\text {--}V\)) characteristics of the fabricated Al/p-Si Schottky diodes with the polythiopene–SiO\(_{2}\) nanocomposite (\(\hbox {PTh--SiO}_{2}\)) interlayer were investigated. The ideality factor of \(\hbox {Al}/\hbox {PTh--SiO}_{2}/{p}\text {-Si}\) Schottky diodes has decreased with increasing temperature and the barrier height has increased with increasing temperature. The change in the barrier height and ideality factor values with temperature was attributed to inhomogeneties of the zero-bias barrier height. Richardson plot has exhibited curved behaviour due to temperature dependence of barrier height. The activation energy and effective Richardson constant were calculated as 0.16 eV and \(1.79 \times 10^{-8} \hbox {A\,cm}^{-2} \,\hbox {K}^{-2}\) from linear part of Richardson plots, respectively. The barrier height values determined from capacitance–voltage–temperature (\(C\text {--}V\text {--}T\)) measurements decrease with increasing temperature on the contrary of barrier height values obtained from \(I\text {--}V\text {--}T\) measurements.

On the conduction mechanisms of Au/(Cu2O–CuO–PVA)/n-Si (MPS) Schottky barrier diodes (SBDs) using current–voltage–temperature (I–V–T) characteristics

The temperature effect on the conduction mechanism of Au/Cu2O–CuO–PVA/n-Si (MPS) type Schottky barrier diodes (SBDs) have been investigated in detail in the wide temperature range of 100–380 K by using the forward bias current–voltage (I–V) measurements. It is observed that the semi logarithmic forward bias I–V plots have two distinct linear regions with different slopes for each temperature. These regions are called low bias region (LBR) and moderate bias region (MBR), respectively. The LBR and MBR correspond to (0.6–1.04 V) and (1.10–1.65 V) bias voltages, respectively. Main diode parameters such as reverse saturation current (I0), ideality factor (n) and zero-bias barrier height (Φb0) were calculated for these two regions. It is observed that the values of Φb0 increased as the values of n decreased with the increasing temperature and such behavior of Φb0 and n with temperature was attributed to the barrier inhomogeneities by assuming Gaussian distribution (GD) at the M/S interface. The Φb0 versus n and q/2kT plots were drawn to get an evidence of the GD. These two plots also have two linear regions at LBR and MBR. These regions are called the low temperature region (LTR) and high temperature region (HTR). Thus the mean values of barrier height (BH) and standard deviation (σs) were obtained by using the intercept and slope of these plots. After that, the conventional Richardson plot was drawn [(Ln(I0/T2) − q2σs 2/2k2T2) vs. q/kT] and it also has two linear regions. The main values of BH and effective Richardson constant (A*) were obtained from the slope and intercept of these plots. These values are found as 0.82 eV and 110.7 A/cm2 K2 for LTR and 1.53 eV and 115.5 A/cm2 K2 for HTR in the LBR and 0.77 eV and 111.9 A/cm2 K2 for LTR and 1.26 eV and 133.9 A/cm2 K2 for HTR in the MBR, respectively. The obtained values of A* are in good agreement with their theoretic values (112 A/cm2 K2) especially for HTR. Thus, the I–V–T characteristics of MPS type SBDs are successfully explained by the double GD model. Besides, the interface state density (Nss) of the MPS diode was calculated from forward-bias I–V measurements.

Numerical simulations of the electrical transport characteristics of a Pt/n-GaN Schottky diode

In this paper, using a numerical simulator, we investigated the current–voltage characteristics of a Pt/n-GaN thin Schottky diode on the basis of the thermionic emission (TE) theory in the 300 to 500 K temperature range. During the simulations, the effect of different defect states within the n-GaN bulk with different densities and spatial locations is considered. The results show that the diode ideality factor and the threshold voltage decrease with increasing temperature, while at the same time, the zero-bias Schottky barrier height (Φb0) extracted from the forward current density–voltage (J–V) characteristics increases. The observed behaviors of the ideality factor and zero-bias barrier height are analyzed on the basis of spatial barrier height inhomogeneities at the Pt/GaN interface by assuming a Gaussian distribution (GD). The plot of apparent barrier height (Φb,App) as a function of q/2kT gives a straight line, where the mean zero-bias barrier height () and the standard deviation (σ0) are 1.48 eV and 0.047 V, respectively. The plot of the modified activation energy against q/kT gives an almost the same value of and an effective Richardson constant A* of 28.22 A cm−2 K−2, which is very close to the theoretical value for n-type GaN/Pt contacts. As expected, the presence of defect states with different trap energy levels has a noticeable impact on the device electrical characteristics.

On the temperature dependent current transport mechanisms and barrier inhomogeneity in Au/SnO2–PVA/n-Si Schottky barrier diodes

In this paper, we report the preparation and characterization of SnO2–PVA nanocomposite film as interlayer for Schottky barrier diodes (SBDs). The possible current transport mechanisms (CTMs) of the prepared SBDs were investigated using the forward-bias current–voltage (I–V) characteristics in the temperature range of 80–400 K. The structure of nanocomposite film was characterized by an X-ray diffractometer (XRD) and the surface morphology was investigated using a Scanning Electron Microscopy (SEM) at room temperature. The values of ideality factor (n) and zero-bias barrier height ( $$\overline{\varPhi }_{\text{Bo}}$$ ) showed variation with temperature, such that they changed from 19.10 to 3.77 and 0.190 to 0.844 eV, respectively. $$\overline{\varPhi }_{\text{Bo}}$$ –n, $$\overline{\varPhi }_{\text{Bo}}$$ −q/2kT, and n −1−q/2kT plots were drawn to get evidence to the Gaussian Distribution (GD) of the barrier height (BH). These plots revealed two distinct linear regions with different slopes for low temperatures (80–160 K) (LTs) and high temperatures (180–400 K) (HTs). This behavior is an evidence to the existence double GD of BHs which provides an average value for BH ( $$\overline{\varPhi }_{\text{Bo}}$$ ) and a standard deviation (σs) for each region. The high value of n especially at low temperatures was attributed to the existence of interlayer: interface states (N ss) and barrier inhomogeneity at Au/n-Si interface. The values of $$\overline{\varPhi }_{\text{Bo}}$$ and σs were obtained from the intercept and slope of mentioned plots as 0.588 and 0.0768 V for LTs and 1.183 eV and 0.158 V for HTs, respectively. Moreover, the modified ln(I s/T 2)−q 2σ s 2 /2k 2 T 2 vs q/kT plot also showed two linear regions. The values of $$\overline{\varPhi }_{\text{Bo}}$$ and effective Richardson constant (A *) were extracted from the slope and intercept of this plot as 0.610 eV and 93.13 A/cm2 K2 for LTs and 1.235 eV and 114.65 A/cm2 K2 for HTs, respectively. The value of A* for HTs is very close to the theoretical value (112 A/cm2 K2) of n-type Si. Thus, the forward-bias I–V–T characteristics of Au/SnO2–PVA/n-Si (SBDs) were successfully explained in terms of the thermionic-emission (TE) mechanism with a double GD of BHs.

Effective Richardson Constant of Sol-Gel Derived TiO2Films in n-TiO2/p-Si Heterojunctions

The effective Richardson constant of sol–gel derived TiO2 thin film has been estimated possibly for the first time from temperature-dependent current–voltage ( ${I}$ – ${V}$ – ${T}$ ) characteristics of p-Si/n-TiO2 thin-film heterojunction diode by including the barrier height inhomogeneity at p-Si/n-TiO2 interface. The thermionic emission theory-based ${I}$ – ${V}$ – ${T}$ characteristics have been modified by assuming a Gaussian distributed barrier height at the heterojunction interface. The Richardson plot shows a nearly ideal Richardson constant of ~1265.57 Acm−2K−2, which is not only very close to its theoretical value of ~1200 Acm−2K−2 for n-TiO2 (with ${m} ^{\ast }_{n}= 10 {m} _{0}$ ), but also the first result reported.