[en] Full text: A metallic poly-pyrrole film has been directly formed on a p-type Si substrate by means of an anodization method under conditions of constant current density by an electrolyte being held at a constant temperature of 55 deg. C that was composed of 0.40 M pyrrole and 0.10 M tetrabutylammonium tetrafluoroborate. An aluminum electrode was used as an ohmic contact. The poly-pyrrole/p-Si/Al structure has demonstrated clearly rectifying behavior by the current-voltage curves studied at room temperature. The capacitance-voltage-frequency curves of the structure have been measured at different frequencies at room temperature in dark. In order to observe the effect of the ageing, the measurements were also repeated 7, 15, 30, 60 and 90 days after fabrication of the poly-pyrrole /p-Si/Al structure. Interface states distribution curves obtained from the capacitance-frequency characteristics with respect to increasing ageing time. During the whole measurement process, the probe of holder on sample was fixed to eliminate effects of surface inhomogeneity

[en] Full text: A metallic poly-pyrrole film has been directly formed on a p-type Si and n-type GaAs substrates by using anodization method under conditions of constant current density. To form ohmic contacts to back sides of Si and GaAs semiconductors Al and Au-Ge alloy were used, respectively. The poly-pyrrole/p-Si/Al and poly pyrrole/n-GaAs/Au-Ge semiconductor structures has demonstrated rectifying behavior by the current-voltage curves studied at room temperature. The samples were exposed to X-ray irradiation up to 50 keV at constant doses in order to determine effect of X-ray radiation. It has been shown that the parameters of the structures such as barrier height, ideality factor and raises resistance have not been changed significantly by the irradiation. As a result, the poly-pyrrole/p-Si/Al and poly-pyrrole/n-GaAs/Au-Ge structures can be used as reliable device at different circuit applications

[en] Sputtered Cr/n-GaAs Schottky diodes have been prepared and annealed at 200 and 400 deg. C. The current-voltage (I-V) characteristics of the as-deposited and annealed diodes have been measured in the temperature range of 60-320 K with steps of 20 K. The effect of thermal annealing on the temperature-dependent I-V characteristics of the diodes has been investigated experimentally. The ideality factor and barrier height (BH) values for 400 deg. C annealed diode approximately remain unchanged from 120 to 320 K, and those of the as-deposited sample from 160 to 320 K. The departures from ideality at low temperatures have been ascribed to the lateral fluctuations of the BH. The BH values of 0.61 and 0.74 eV for the as-deposited and 400 deg. C annealed diodes were obtained at room temperature, respectively. A Richardson constant value of 9.83 A cm^-2 K^-2 for 400 deg. C annealed Schottky diode, which is in close agreement with the known value of 8.16 A cm^-2 K^-2 for n-type GaAs. Furthermore, T₀ anomaly values of 15.52, 10.68 and 5.35 for the as-deposited and 200 and 400 deg. C annealed diodes were obtained from the nT versus T plots. Thus, it has been seen that the interface structure and quality improve by the thermal annealing at 400 deg. C.

[en] Exceptional properties such as dielectric, ferroelectric, piezoelectric, magnetic, catalytic, and photovoltaic of perovskite materials open new doors to many groundbreaking discoveries for unique device ideas. These materials properties are inherited from their crystal structures; therefore, the features can be tuned via varying details of the crystal structures. In the literature, LaCrO₃ (LCO) is one those mostly examined perovskites for various purposes such as solid oxide fuel cells, catalytic converters, and sensors. In the present study, the band gap tuning of LCO was investigated via doping a transition element such as cobalt (Co), palladium (Pd), and iridium (Ir) into Cr atom. The synthesized doped and un-doped LCO powders were characterized by infrared spectra (IR) and X-ray diffraction (XRD). Scanning electron microscopy (SEM) was employed to study the surface topography of LCO and doped LCO thin films on silicon substrates. The band gaps of the LCO and doped LCO films were scrutinized using a UV–Vis spectrometer. Our study has shown that the band gap of LCO was successfully lowered from 3.4 eV to 2.66 eV and can be engineered via substitution at various mol% of transition elements (Co, Pd, Ir) onto B-site Cr atom in the LCO perovskite structure.

[en] In this study, we fabricated an Al/Azure A/p-Si heterojunction. The electrical characterization and photovoltaic properties of the Al/Azure A/p-Si heterojunction were investigated by current–voltage (I–V) under dark and illuminated conditions at room temperature. The photovoltaic device gives V_oc = 340 mV and I_sc = 807 μA under 30 mW cm⁻². The device was found to have a fill factor (FF) and power conversion efficiency (η_P) 36% and 4.07%, respectively. The values of some diode parameters were determined using thermionic emission theory. Some diode parameters, such as the ideality factor (n) and barrier height (ϕ_b) values, were found to be 1.26 and 0.78 eV, respectively. An ideality factor higher than 1 can be explained on the basis of the inhomogeneity barrier-height model or as a result of natural oxide layers. The results obtained from electrical and photovoltaic properties show that the device can be used as photodiode and in opto-electronic circuit applications. (paper)

[en] We have fabricated two groups of Cr/n-GaAs Schottky diodes (SDs) by magnetron sputtering technique to determine whether T₀ anomaly varies in similarly fabricated SDs or not. Firstly, the first group diodes were inserted into a vacuum chamber to form the Schottky contacts, then the second group diodes which are held in the clean room medium for 3 h before Schottky metal deposition. The current-voltage (I-V) characteristics of three diodes (the dots of the sample CrD1) from the first group and two diodes (the dots of the sample CrD2) from the second group were measured in temperature range of 60-320 K. The barrier heights increased with increasing temperature in range of 60-160 K, and did not changed in range of 160-320 K. Ideality factory value decreased with increasing temperature in range of 60-160 K and changed between 1.05 and 1.10 in range of 160-320 K. T₀ anomaly values were calculated from straight lines fitted to nT'-T plots. The fits to the experimental values of nT-T plots are parallel to the ideal Schottky contact line, especially for the dots (Schottky diodes) of the sample CrD1. T₀ anomaly values for the dots of the sample CrD1 were obtained as 13.9, 11.20 and 13.31 K; and the values of 19.74 and 19.20 K was obtained for the dots of the sample CrD2. It has been concluded that the T₀ anomaly values for the similarly fabricated diodes (the dots of the sample CrD1 or the CrD2) are almost very close to each other within the margins of experimental error

[en] We have fabricated the Au/Ni/n-GaN structures and measured their capacitance–frequency (C–f) and conductance (G/w)-angular frequency (w) characteristics in the temperature range of 60–320 K. The C–f curves for different reverse bias voltages have shown a behavior almost independent of the bias voltage at frequencies above 300 kHz at each measurement temperature. We have calculated the temperature-dependent interface state density, N_s_s, values from the G/w versus w curves. The N_s_s value for the Ni/n-GaN interface ranges from 3.36 × 10"1"1 cm"−"2 eV"−"1 at 0.0 V to 2.92 × 10"1"1 cm"−"2 eV"−"1 at 0.40 V for 60 K, and 6.63 × 10"1"1 cm"−"2 eV"−"1 at 0.0 V to 3.87 × 10"1"1 cm"−"2 eV"−"1 at 0.40 V for 320 K. That is, the interface state density value increases with increasing temperature. It has been seen that the values of N_s_s obtained from the G/w versus w curves of the device are lower than the given values for metal/n-type GaN interface in the literature. (paper)

[en] In this study, Ti/n-GaAs Schottky barrier diode has been fabricated by DC magnetron sputtering. The current–voltage, capacitance–voltage, and conductance–voltage characteristics of Ti/n–GaAs diode have been investigated in the temperature range of 80–320 K. The ideality factor and barrier height values have been calculated from the forward current–voltage characteristics. The variation of the diode parameters with the sample temperature has been attributed to the presence of the lateral inhomogeneities of the barrier height. The temperature dependent capacitance–voltage characteristics have been measured to calculate the carrier concentration, diffusion potential, barrier height, and temperature coefficient of the barrier height (α = −0.65 meV K⁻¹). The fact that the temperature coefficient of the barrier height changes from metal to metal has been ascribed to the chemical nature of the contact metal or metal electronegativity

[en] Au/Ti/HfO₂/n-GaAs MIS (metal/insulating layer/semiconductor) diodes were fabricated by atomic layer deposition technique and their electrical properties were investigated in detail by the help of current–voltage (I–V) and admittance measurements in the temperature range of 60–320 K. Together with the surface morphology analysis on the HfO₂ thin-film layer, main electrical parameters such as series resistance (R_s), zero bias barrier height (Φ_Bo), ideality factor (n), impedance (Z) and phase angle were determined and effects of temperature on these parameters of the MIS diodes were discussed. The evaluation of I–V data exhibits a decrease in R_s and Φ_Bo, however an increase in n, with a decrease in temperature. Temperature-dependent conductance (G) and capacitance (C) characteristics of the MIS diode were investigated at 1000 kHz in the voltage interval in between − 3 and 2 V. G and C values were found in a direct relation with the change in temperature. On the other hand, Z values showed an inverse proportionality with temperature. The phase angle versus voltage plots were evaluated at different temperatures (60–320 K) at 1000 kHz and the obtained results indicated that the device behaves more capacitive in the voltage range of − 3 V and about 0.4 V for all temperature, and phase angle decreases with increasing temperature from 0.4 to 1.6 V. In addition, the interface state density (D_it), the effective oxide charge density (Q_eff) and effective number of charges per unit area (N_eff) of the fabricated diodes were investigated over temperature range 60–320 K in which these values were found in a decreasing trend with increasing temperature.

[en] The Ni/p-InP Schottky diodes (SDs) have been prepared by DC magnetron sputtering deposition. After the diode fabrication, they have been thermally annealed at 700 °C for 1 min in N₂ atmosphere. Then, the current–voltage characteristics of the annealed and non-annealed (as-deposited) SDs have been measured in the measurement temperature range of 60–400 K with steps of 20 K under dark conditions. After 700 °C annealing, an improvement in the ideality factor value has been observed from 60 to 200 K and the barrier height (BH) value approximately has remained unchanged in the measurement temperature range of 200–400 K. The BH of the annealed diode has decreased obeying the double-Gaussian distribution (GD) of the BHs with decreasing measurement temperature from 200 to 60 K. The BH for the as-deposited diode has decreased with decreasing temperature obeying the single-GD over the whole measurement temperature range. An effective Richardson constant value of 54.21 A/cm²K² for the as-deposited SD has been obtained from the modified Richardson plot by the single-GD plot, which is in very close agreement with the value of 60 A/K²cm² for p-type InP. The series resistance value of the annealed SD is lower than that of the non-annealed SD at each temperature and approximately has remained unchanged from 140 to 240 K. Thus, it can be said that an improvement in the diode parameters has been observed due to the thermal annealing at 700 °C for 1 min in N₂ atmosphere. (paper)