The effects of the temperature and annealing on current-voltage characteristics of Ni/n-type 6H-SiC Schottky diode

The temperature dependence of current-voltage (I-V) characteristics of as-fabricated and annealed Ni/n-type 6H-SiC Schottky diode has been investigated in the temperature range of 100-500 K. The forward I-V characteristics have been analysed on the basis of standard thermionic emission theory. It has been shown that the ideality factor (n) decreases while the barrier height (Φ_b) increases with increasing temperature. The values of Φ_b and n are obtained between 0.65-1.25 eV and 1.70-1.16 for as-fabricated and 0.74-1.70 eV and 1.84-1.19 for annealed diode in the temperature range of 100-500 K, respectively. The I-V characteristics of the diode showed an increase in the Schottky barrier height, along with a reduction of the device leakage current by annealing the diode at 973 K for 2 min.     

Electrical characterization of current conduction in Au/TiO2/n-Si at wide temperature range

In this study, we have examined Au/TiO₂/n-Si Schottky barrier diodes (SBDs), in order to interpret in detail the experimental observed non-ideal current–voltage–temperature (I–V–T) characteristics. I–V characteristics were measured in the wide temperature range of 80–400 K. TiO₂ was deposited on n-Si substrate by reactive magnetron sputtering. The zero-bias barrier height (ϕ_B0) and ideality factor (n) show strong temperature dependence. While n decreases, ϕ_B0 increases with increasing temperature. Experimental results show that the current across the SBDs may be greatly influenced by the existence of Schottky barrier height (SBH) inhomogeneity. These temperature behaviors have been explained on the basis of the thermionic emission (TE) theory with Gaussian distribution (GD) of the barrier heights (BHs) due to BH inhomogeneities at metal–semiconductor (M/S) interface. From this assumptions, obtaining Richardson constant value of the A^* 121.01 A/cm² K² is perfect agreement with the theoretical value of 120 A/cm² K² for n-type Si. Hence, behaviors of the forward-bias I–V characteristics of the Au/TiO₂/n-Si (SBDs) can be successfully explained on the basis of a TE mechanism with a double Gaussian distribution of the BHs.     

The analysis of I-V characteristics of Schottky diodes by thermionic emission with a Gaussian distribution of barrier height

The current-voltage (I-V) characteristics of Al/p-Si Schottky barrier diode (SBD) with native insulator layer were measured in the temperature range of 178-440 K. The estimated zero-bias barrier height Φ_B0 and the ideality factor n assuming thermionic emission (TE) theory have shown strong temperature dependence. Evaluation of the forward I-V data have revealed an increase of zero-bias barrier height Φ_B0 but the decrease of ideality factor n with the increase in temperature. The experimental and theoretical results of the tunneling current parameter E_o against kT/q were plotted to determine predominant current-transport mechanism. But the experimental results were found to be disagreement with the theoretical results of the pure TE, the thermionic-field emission (TFE) and the field emission (FE) theories. The conventional Richardson plot has exhibited non-linearity below 240 K with the linear portion corresponding to the activation energy of 0.085 eV and Richardson constant (A^*) value of 2.48 × 10⁻⁹ A cm⁻² K⁻² which is much lower than the known value of 32 A cm⁻² K⁻² for holes in p-type Si. Such behaviours were attributed to Schottky barrier inhomogeneities by assuming a Gaussian distribution of barrier heights (BHs) due to barrier height inhomogeneities that prevail at interface. Thus, the modified ln(I_o/T²) − q2σo2/2k²T² vs q/kT has plotted. Then A^* was calculated as 38.79 A cm⁻² K⁻² without using the temperature coefficient of the barrier height. This value of the Richardson constant 38.79 A cm⁻² K⁻² is very close to the theoretical value of 32 A K⁻² cm⁻² for p-type Si. Hence, it has been concluded that the temperature dependence of the forward I-V characteristics of the Al/p-Si Schottky barrier diodes with native insulator layer can be successfully explained on the basis of TE mechanism with a Gaussian distribution of the barrier heights.     

Transport properties of Gallium Phosphide based Schottky contact with thin insulating layer

The current-voltage (I-V) characteristics of Au/n-GaP Schottky barrier diode was analyzed in wide temperature range of 220–400 K. The conduction mechanism in the low bias region, except for 220 K and 240 K, was identified as tunneling (TN). Nevertheless, thermionic emission (TE) becomes dominant as the voltage increases. The diode parameters were evaluated in this region by TE model incorporating the concept of thin insulating layer. The series resistance (R_s) of the device was found to decrease with increase in temperature. In the 220–320 K temperature range, as reported for most of the Schottky diodes, the zero-bias barrier height (ϕ_b0) decreases and the ideality factor (η) increases with the decrease of temperature. The value of modified Richardson constant (A**) obtained agrees well with the theoretical value. However, in the 320–400 K range, the variation of η and ϕ_b0 with temperature shows opposite trend, which is speculated as due to the change in conduction pattern by the temperature induced modifications at the interface.     

Study and modeling of the transport mechanism in a Schottky diode on the basis of a GaAs semiinsulator

The current through a metal-semiconductor junction is mainly due to the majority carriers. Three distinctly different mechanisms exist in a Schottky diode: diffusion of the semiconductor carriers in metal, thermionic emission-diffusion (TED) of carriers through a Schottky gate, and a mechanical quantum that pierces a tunnel through the gate. The system was solved by using a coupled Poisson-Boltzmann algorithm. Schottky BH is defined as the difference in energy between the Fermi level and the metal band carrier majority of the metal-semiconductor junction to the semiconductor contacts. The insulating layer converts the MS device in an MIS device and has a strong influence on its current-voltage (I-V) and the parameters of a Schottky barrier from 3.7 to 15 eV. There are several possible reasons for the error that causes a deviation of the ideal behaviour of Schottky diodes with and without an interfacial insulator layer. These include the particular distribution of interface states, the series resistance, bias voltage and temperature. The GaAs and its large concentration values of trap centers will participate in an increase in the process of thermionic electrons and holes, which will in turn act on the I-V characteristic of the diode, and an overflow maximum value [NT = 3 × 10²⁰] is obtained. The I-V characteristics of Schottky diodes are in the hypothesis of a parabolic summit.     

Accurate surface potential determination in Schottky diodes by use of correlated current and capacitance voltage measurements. Application to n–InP

Based on current voltage (I-V_g) and capacitance voltage (C-V_g) measurements, a reliable procedure is proposed to determine the effective surface potential V_d.V_g/ in Schottky diodes. In the framework of thermionic emission, our analysis includes both the effect of the series resistance and the ideality factor, even voltage dependent. This technique is applied to n-type indium phosphide (n-InP) Schottky diodes with and without an interfacial layer and allows us to provide an interpretation of the observed peak on the C-V_g measurements. The study clearly shows that the depletion width and the flat band barrier height deduced from C-V_g, which are important parameters directly related to the surface potential in the semiconductor, should be estimated within our approach to obtain more reliable information.     

Numerical simulation study of current–voltage characteristics of a Schottky diode with inverse doped surface layer

The Poisson’s equation and drift–diffusion equations are used to simulate the current–voltage characteristics of Schottky diode with an inverse doped surface layer. The potential inside the bulk semiconductor near the metal–semiconductor contact is estimated by simultaneously solving these equations, and current as a function of bias through the Schottky diode is calculated for various inverse layer thicknesses and doping concentrations. The Schottky diode parameters are then extracted by fitting of simulated current–voltage data into thermionic emission diffusion equation. The obtained diode parameters are analyzed to study the effect of inverse layer thickness and doping concentration on the Schottky diode parameters and its behavior at low temperatures. It is shown that increase in inverse layer thickness and its doping concentration give rise to Schottky barrier height enhancement and a change in the ideality factor. The temperature dependences of Schottky barrier height and ideality factor are studied. The effect of temperature dependence of carrier mobility on the Schottky diode characteristics is also discussed.     

Barrier characteristics of gold Schottky contacts on moderately doped n-InP based on temperature dependent I-V and C-V measurements

The temperature dependences of current-voltage (I-V) and capacitance-voltage (C-V) characteristics of the gold Schottky contacts on moderately doped n-InP (Au/MD n-InP) Schottky barrier diodes (SBDs) have been systematically investigated in the temperature range of 60-300 K. The main diode parameters, ideality factor (n) and zero-bias barrier height (apparent barrier height) were found to be strongly temperature dependent and while the decreases, the n and the increase with decreasing temperature. According to Thermionic Emission (TE) theory, the slope of the conventional Richardson plot [In(J₀/T²) vs. 1000/T] should give the barrier height. However, the experimental data obtained do not correlate well with a straight line below 160 K. This behaviour has been interpreted on the basis of standard TE theory and the assumption of a Gaussian distribution of the barrier heights due to barrier inhomogeneities that persist at the metal-semiconductor interface. The linearity of the apparent barrier height vs. 1/(2kT) plot that yields a mean barrier height of 0.526 eV and a standard deviation (σ_s0) of 0.06 eV, was interpreted as an evidence to apply the Gaussian distribution of the barrier height. Furthermore, modified Richardson plot [ vs. 1/T] has a good linearity over the investigated temperature range and gives the and the Richardson constant (A^∗) values as 0.532 eV and 15.90 AK⁻²cm⁻², respectively. The mean barrier heights obtained from both plots are appropriate with each other and the value of A^∗ obtained from the modified Richardson plot is close to the theoretical value of 9.4 AK⁻²cm⁻² for n-InP. From the C-V characteristics, measured at 1 MHz, the capacitance was determined to increase with increasing temperature. C-V measurements have resulted in higher barrier heights than those obtained from I-V measurements. The discrepancy between Schottky barrier heights(SBHs) obtained from I-V and C-V measurements was also interpreted. As a result, it can be concluded that the temperature dependent characteristic parameters for Au/MD n-InP SBDs can be successfully explained on the basis of TE mechanism with Gaussian distribution of the barrier heights.     

Temperature dependent current–voltage (I–V) characteristics of Au/n-Si (1 1 1) Schottky barrier diodes with PVA(Ni,Zn-doped) interfacial layer

Current–voltage (I–V) characteristics of Au/PVA/n-Si (1 1 1) Schottky barrier diodes (SBDs) have been investigated in the temperature range 80–400 K. Here, polyvinyl alcohol (PVA) has been used as interfacial layer between metal and semiconductor layers. The zero-bias barrier height (Φ_B0) and ideality factor (n) determined from the forward bias I–V characteristics were found strongly dependent on temperature. The forward bias semi-logarithmic I–V curves for different temperatures have an almost common cross-point at a certain bias voltage. The values of Φ_B0 increase with the increasing temperature whereas those of n decrease. Therefore, we have attempted to draw Φ_B0 vs. q/2kT plot in order to obtain evidence of a Gaussian distribution (GD) of the barrier heights (BHs). The mean value of BH and standard deviation (σ₀) were found to be 0.974 eV and 0.101 V from this plot, respectively. Thus, the slope and intercept of modified vs. q/kT plot give the values of and Richardson constant (A^?) as 0.966 eV and 118.75 A/cm²K², respectively, without using the temperature coefficient of the BH. This value of A^* 118.75 A/cm²K² is very close to the theoretical value of 120 A/cm²K² for n-type Si. Hence, it has been concluded that the temperature dependence of the forward I–V characteristics of Au/PVA/n-Si (1 1 1) SBDs can be successfully explained on the basis of the Thermionic Emission (TE) theory with a GD of the BHs at Au/n-Si interface.     

Current–voltage and capacitance–voltage characteristics of Al Schottky contacts to strained Si-on-insulator in the wide temperature range

The electrical characteristics of Al/strained Si-on-insulator (sSOI) Schottky diode have been investigated using current–voltage (I–V) and capacitance–voltage (C–V) measurements in the wide temperature range of 200–400 K in steps of 25 K. It was found that the barrier height (0.57–0.80 eV) calculated from the I–V characteristics increased and the ideality factor (1.97–1.28) decreased with increasing temperature. The barrier heights determined from the C–V measurements were higher than those extracted from the I–V measurements, associated with the formation of an inhomogeneous Schottky barrier at the interface. The series resistance estimated from the forward I–V characteristics using Cheung and Norde methods decreased with increasing temperature, implying its strong temperature dependence. The observed variation in barrier height and ideality factor could be attributed to the inhomogeneities in Schottky barrier, explained by assuming Gaussian distribution of barrier heights. The temperature-dependent I–V characteristics showed a double Gaussian distribution with mean barrier heights of 0.83 and 1.19 eV and standard deviations of 0.10 and 0.16 eV at 200–275 and 300–400 K, respectively. From the modified Richardson plot, the modified Richardson constant were calculated to be 21.8 and 29.4 A cm⁻² K⁻² at 200–275 and 300–400 K, respectively, which were comparable to the theoretical value for p-type sSOI (31.6 A cm⁻² K⁻²).     

The analysis of the electrical characteristics and interface state densities of Re/n-type Si Schottky barrier diodes at room temperature

The main electrical characteristics of current-voltage (I-V) and capacitance-voltage (C-V) measurements at room temperature of the Re/n-type Si Schottky barrier diodes prepared by pulsed laser deposition (PLD) method have been examined. The values of the basic electrical properties such as forward saturation current (I_o), ideality factors (n), barrier heights (Ф_bo), rectification ratio (RR) and series resistances (R_S) were obtained from I-V and C-V measurements using different calculation methods. At low voltages (V ≤ 0.3 V), the electrical conduction was formed to take place by thermionic emission, whereas at high voltages (V > 0.3 V), a space charge limited conduction mechanism was shown. Furthermore, the interface state densities (N_SS) as a function of energy distribution (E_SS- E_V) was obtained from the I-V data by taking into account the bias dependence of the effective barrier height (Φ_b) for the Re/n-type Si Schottky barrier diodes.     

Electrical and photovoltaic properties of a n-Si/chitosan/Ag photodiode

The electrical and photovoltaic properties of AuSb/n-Si/chitosan/Ag diode have been investigated. The ideality factor, barrier height and Richardson constant values of the diode at room temperature were found to be 1.91, 0.88 eV and 121.4 A/cm² K², respectively. The ideality factor of the diode is higher than unity, suggesting that the diode shows a non-ideal behaviour due to series resistance and barrier height inhomogeneities. The barrier height and ideality factor values of Ag/CHT/n-Si diode at room temperature are significantly larger than that of the conventional Ag/n-Si Schottky diode. The φ_B value obtained from C-V measurement is higher than that of φ_B value obtained from I-V measurement. The discrepancy between φ_B(C-V) and φ_B(I-V) barrier height values can be explained by Schottky barrier height inhomogeneities. AuSb/n-Si/chitosan/Ag diode indicates a photovoltaic behaviour with open circuit voltage (V_oc = 0.23 V) and short-circuit current density (J_sc = 0.10 μA/cm⁻²) values.     

Effects of temperature on series resistance determination of electrodeposited Cr/n-Si/Au-Sb Schottky structures

Temperature dependences of the series resistance in the Cr/n-Si/Au-Sb Schottky structures prepared by electrodeposition method have been studied using current-voltage (I-V) characteristics in the 80-320 K temperature range by steps of 20 K. However, the values of series resistance obtained from Cheung functions were compared with each other, and it was seen that there is a good agreement between the values of the series resistance. A modified Norde’s function combined with conventional forward I-V method was used to extract the parameters including barrier height and the series resistance. The barrier height and series resistance obtained from Norde’s function were compared with those from Cheung functions. The values of barrier height and series resistance have very different especially towards to the lower temperatures. This is attributed to non-ideal I-V characteristics of the Cr/n-Si/Au-Sb Schottky structure and non-pure thermionic emission theory due to the low temperature effects.     

Schottky barrier modification on InP using shallow implant layer

Enhanced Schottky barriers are formed on n-InP, using a shallow doped surface layer of type opposite to that of the substrate. The doped surface layer helps in retarding the surface fields, resulting in larger Schottky barrier heights. The Schottky barrier height is found to increase by as much as 0.30–0.35 eV, which is one of the highest that has been obtained for Al/n-InP. Also, the reverse leakage current is reduced by almost three orders of magnitude. However, the ideality factor, at low current levels, is found to be slightly greater than unity (≈1.2). To demonstrate the versatility of our process, the same technique is applied to p-InP samples. As expected, the barrier height is reduced by almost 0.5 eV. The ideality factor for p-type Schottky diodes is found to be very close to unity (≈1.02-1.05) over the entire range of beryllium dosage. The sum of the two Schottky barrier heights is also found to be quite close to the theoretical value of energy bandgap for InP.     

Electrical characterization and DLTS analysis of a gold/n-type gallium nitride Schottky diode

This work describes a comparison of current density–voltage (J–V) and capacitance–voltage (C–V) properties measured as a function of temperature; deep trap properties are measured by deep level transient spectroscopy (DLTS) of Schottky diodes fabricated on n-type gallium nitride (GaN grown by metal organic vapor phase epitaxy (MOVPE). Unexpected behavior in the standard Richardson plot was observed in the temperature range 165–480 K, reflecting a range of Schottky barrier heights and a variation of ideality factor. This was explained by applying a Gaussian spatial distribution of barrier heights across the Schottky diode. C–V measurements were carried out in the temperature range 165–480 K to compare the temperature dependence of the barrier height with those obtained by the Gaussian distribution method. DLTS and high-resolution Laplace DLTS (LDLTS) show a majority carrier peak centered at 450 K.     

Effect of Inverse Doped Surface Layer in Schottky Barrier Modification: A Numerical Study

Poisson’s equation and the drift–diffusion equations are used to simulate the current–voltage characteristics of a Schottky diode with an inverse doped surface layer. The potential inside the bulk semiconductor near the metal–semiconductor contact is estimated by simultaneously solving these equations, and then current as a function of bias through the Schottky diode is calculated. The Schottky diode parameters are extracted by fitting of simulated data to the thermionic emission diffusion equation. The simulation is carried out for various inverse layer thicknesses and doping concentrations. The obtained diode parameters are analyzed to study the effect of the inverse layer thickness and doping concentration on Schottky diode modification and its behavior at low temperatures. It is shown that an increase in the inverse layer thickness and doping concentration leads to Schottky barrier height enhancement and a change in the ideality factor. The temperature dependences of the Schottky barrier height and ideality factor are also studied.     

Fabrication and electrical characterization of Al/p-ZnIn2Se4 thin film Schottky diode structure

Polycrystalline thin films of ternary ZnIn₂Se₄ compound with p-type conductivity were deposited on a pre-deposited aluminium (Al) film by a flash evaporation technique. A Schottky diode comprising of Al/p-ZnIn₂Se₄ structure was fabricated and characterized in the temperature range 303–323 K in dark condition. The Schottky diode was subjected to current (I)-voltage (V) and capacitance (C)-voltage (V) characterization. The Al/p-ZnIn₂Se₄ Schottky diode showed behaviour typical of a p-n junction diode. The devices showed very good diode behaviour with the rectification ratio of about 10⁵ at 1.0 V in dark. The Schottky diode ideality factor, barrier height, carrier concentration, etc. were derived from I-V and C-V measurements. At lower applied voltages (V≤0.5 V), the electrical conduction was found to take place by thermionic emission (TE) whereas at higher voltages (V>0.5 V), a space charge limited conduction mechanism (SCLC) was observed. An energy band diagram was constructed for fabricated Al/p-ZnIn₂Se₄ Schottky diode.     

The effect of annealing temperature and the characteristics of p-n junction diodes based on sprayed polyaniline/ZnO thin films

Polyaniline,ZnO and polyaniline/ZnO nanocomposite thin films are coated on glass substrates using the spray pyrolysis technique.The samples are characterized by the XRD,SEM,EDAX,UV-Vis and I-V characteristics. The XRD analyses confirm that the spray-coated polyaniline and ZnO thin films have orthorhombic and hexagonal structures,respectively,and optical bandgap energy decreases from 3.81 to 3.41 eV with the addition of a Zn atom.SEM analysis of the polyaniline/ZnO nanocomposite thin films shows that there is an agglomeration of ZnO particles with uniform distribution in the polyaniline matrix,and the diode characteristics of the polyaniline /ZnO nanocomposite show weak rectification behavior.Parameters such as the ideality factor,reverse saturation current and barrier height are calculated from the I-V characteristics.     

A theoretical analysis together with experimental data of inhomogeneous Schottky barrier diodes

We have shown that the current at lower temperatures may exceed the current at higher temperatures using the approximation of the apparent BH in the inhomogeneous SDs, as determined by some authors in the literature. Then, in the simulated forward I-V curves of non-interactive inhomogeneous SDs using the approximation of the apparent BH, it has been showed that the current at lower temperatures does not exceed the current at higher temperatures when considering the bias voltage dependence of apparent BH. In the calculations, the parameters from the experimental forward bias I-V characteristics, in the temperature range of 60-300 K, of the Ni/n-GaAs Schottky contacts with the inhomogeneous BH have been used by means of the thermionic emission theory of inhomogeneous Schottky contacts, considering a Gaussian distribution of barrier heights with a linear bias dependence.