Zero-bias Barrier Height Values Research Articles

Investigation of the electrical properties of diodes by crosschecking dependence on the presence of (nanocarbon-PVP) interface layer

The Al/p-Si (metal-semiconductor (MS)) and Al/nanocarbon-PVP/p-Si (metal-polymer-semiconductor) type Schottky barrier diodes (SBDs) were fabricated in same conditions to determine the existence of an increase in the performance of Al/p-Si diode and they were called as D1 and D2, respectively. For this purpose, the electrical properties of the diodes were investigated using the current–voltage and impedance–voltage measurements in wide bias voltage. The ideality factor, reverse-saturation current and zero-bias barrier height values were calculated from the linear part of the forward bias lnI–V plot as 6.23, 2.35 ✕ 10–8A, 0.68 eV for D1 and 2.86, 4.27 ✕ 10–9A, 0.73 eV for D2, respectively. It is seen from results that the value of rectifier rate for D2 is about 8 times higher than for D1. The values of barrier height, Fermi energy level, the number of doped acceptor atoms and depletion layer width were obtained. The values of series resistance and special density distribution of interface states’ values also considerably decrease using (nanocarbon Polyvinylpyrrolidone (PVP)) interlayer. All these results confirmed that the nanocarbon-PVP polymer interlayer leads to a seriously increase in the performance of the MS diodes and hence it can be successfully used as an insulator in view of low cost, grown by simple methods.

The Effects of Thermal Neutron Irradiation on Current-Voltage and Capacitance-Voltage Characteristics of Au/n-Si/Ag Schottky Barrier Diodes

To observe the neutron transmutation and displacement damage effects, Au/n-Si/Ag Schottky barrier diodes were exposed to thermal neutron irradiation. Irradiation induced changes in Schottky barrier height, saturation current, and donor concentration were investigated by using current-voltage (I-V) and capacitance-voltage (C-V) characteristics of the diodes. The irradiation for 10 s caused a little change in the Schottky diode parameters which were obtained from I-V and C-V measurements. Observable changes in the parameters occurred after the second irradiation of 30 s duration. After the total dose, an increase in saturation current and barrier height inhomogeneties took into place and a decrease in carrier concentration was observed due to the carrier removal effect of thermal neutron-induced damages. Whereas the values of zero bias barrier height have little change after irradiations, the values of ideality factor increased after irradiations. The values of zero-bias barrier height for all diodes was also calculated from reverse bias current characteristics. After second dose, the values of zero-bias barrier height decreased for all diodes. The values of series resistance were determined by Cheung functions before and after irradiations. Before irradiations, the values were found between 2.10 kΩ and 2.76 kΩ. After second dose, the values of series resistance of all diodes decreased and were found between 1.59 kΩ and 2.20 kΩ. Furthermore, the proof of thermal neutron transmutation of elements in the devices was given via energy dispersive spectroscopy (EDS) mapping.

Electrical characterization of two analogous Schottky contacts produced from N-substituted 1,8-naphthalimide.

The aim of this study was to analyze the interface states (Nss) in pure Al//p-Si/Al, Al/N-F Nft/p-Si/Al and Al/N-T Nft/p-Si/Al Schottky barrier diodes (SBDs). N-Substituted 1,8-naphthalimide thin films were deposited on a p-Si substrate by spin coating and annealed at ∼200 °C for 60 s under an air atmosphere. Al contacts were obtained via reactive magnetron sputtering. The current voltage (I-V) characteristics of the SBDs were measured at room temperature. From the I-V characteristics, the SBDs ideality factor (n) and zero-bias barrier height values (Φb) of 1.27, 1.00, and 1.05 and 0.66 eV, 0.70 eV, and 0.64 eV were observed for the Al//p-Si/Al, Al/N-F Nft/p-Si/Al and Al/N-T Nft/p-Si/Al Schottky barrier diodes, respectively. The interface state density distribution profile (Nss) as a function of (Ess-Ev) was extracted from the forward-bias I-V measurements by considering the effective barrier height and (Φe) and series resistance (Rs) of the Schottky diode. The obtained Nss plot tendency showed that the existence of interface states has no significant effect on the rectifying and capacitance characteristics. The Nss values with the 1,8-naphthalimide layer were lower than that without it. This shows that naphthalimide exhibits a strong contribution by blocking the unwanted states and some traps in the conduction mechanism, which may cause possible cracks or deep paths for carriers to travel along the junction.

Structural and electrical characterization of rectifying behavior in n-type/intrinsic ZnO-based homojunctions

► Some structural and electrical properties of Au/Si/n-ZnO/i-ZnO junctions were reported. ► XRD revealed that n-Si/ZnO have hexagonal structure with a strong (0 0 2) preferred orientation. ► SEM showed that ZnO nanorods grow vertical to the Si substrate with 400–500 nm in diameter. ► Au/Si/n-ZnO/i-ZnO junctions exhibited rectifying behavior with a turn on voltage of 1.2 V at 300 K. ZnO nanorods were synthesized on n-Si substrates by a chemical bath deposition method. X-ray diffraction and scanning electron microscopy results showed that the deposited ZnO nanorods crystallize in the wurtzite structure and are highly textured with their c -axes normal to the substrate and show a clearly hexagonal morphology. A heavily compensated, intrinsic ZnO layer (i-ZnO) doped with both Mg and Na was deposited on the nominally undoped ZnO nanorods (which show a natural n-type behavior) to produce an i-ZnO/n-ZnO homojunction. The i-ZnO layer consisted of hexagonal shaped crystallites oriented mainly perpendicular to the substrate surface. The current–voltage ( I – V ) characteristics of these structures in the temperature range of 100–300 K have been analyzed in the framework of standard thermionic emission (TE) theory with the assumption of a Gaussian distribution of the barrier heights. The values of zero-bias barrier height ( Φ bo ) and ideality factor ( n ) were found to be strongly temperature dependent whereby n decreases while Φ bo increases with increasing temperature. A Richardson plot of our data shows straight line behavior and the values of activation energy ( E a = Φ bo ) and the Richardson constant ( A *) determined from the intercept and slope of the plot were 0.770 eV and 2.61 × 10 −8 A cm −2 K −2 , respectively. The value of A * is much lower than the known value of 32 A cm −2 K −2 for ZnO. Thus, a modified Richardson plot based on a Gaussian distribution of barrier heights was used which yields a mean barrier height ( Φ ¯ b 0 ) and modified effective Richardson ( A **) of 0.782 eV and 39.09 A cm −2 K −2 , respectively. This value of A ** is much closer to the theoretical value of 32 A cm −2 K −2 for ZnO.

Analysis of the forward and reverse bias I-V characteristics on Au/PVA:Zn/n-Si Schottky barrier diodes in the wide temperature range

In this study, the forward and reverse bias current-voltage (I-V) characteristics of Au/Zinc acetate doped polyvinyl alcohol/n-Si Schottky barrier diodes (SBDs) have been investigated over the temperature range of 80-400 K. The values of zero-bias barrier height evaluated from forward and reverse bias I-V data, (ФBFo) and (ФBRo), increase with increasing temperature, and a discrepancy is observed between the values of ФBFo and ФBRo. Because the apparent barrier height (BH) seen from metal to semiconductor is higher than the one seen from semiconductor to metal, the obtained value of ФBFo is always greater than ФBRo value. The difference between them is almost the same as the Fermi energy level. The crossing of the experimental forward bias semilogarithmic ln I-V plots appears as an abnormality when compared to the conventional behavior of ideal SBDs. This behavior was attributed to the lack of free charge at a low temperature and could be expected in the temperature region where there is no carrier freezing out, which is non-negligible at low temperatures. Prior to intersection, the voltage dependent value of resistance (Ri) obtained from Ohm’s law decreases with increasing temperature, but it begins to increase after this intersection point. Such an increase in ФBo and series resistance (Rs) with temperature corresponding to high voltage region is in obvious disagreement with the reported negative temperature coefficients. However, the value of shunt resistance (Rsh) corresponding to a low or negative voltage region decreases with increasing temperature. In addition, the temperature dependent energy density distribution profiles of interface states (Nss) were obtained from forward bias I-V measurements by taking into account the bias dependence of the effective barrier height (Фe) and Rs of the device, and the values of Nss without considering Rs are almost one order of magnitude larger than Nss when considering Rs value.