On the profile of frequency dependent dielectric properties of (Ni/Au)/GaN/Al0.3Ga0.7N heterostructures

The voltage (V) and frequency (f) dependence of dielectric characteristics such as dielectric constant (ε′), dielectric loss (ε^″), dielectric loss tangent (tan δ) and real and imaginary part of electrical modulus (Μ′ and M^″) of the (Ni/Au)/GaN/Al_0.3Ga_0.7N heterostructures have been investigated by using experimental admittance spectroscopy (capacitance-voltage (C-V) and conductance-voltage (G/w-V)) measurements at room temperature. Experimental results show that the values of the ε′, ε^″, tan δ and the real and imaginary parts of the electric modulus (Μ′ and M^″) obtained from the C and G/w measurements were found to be strong function of frequency and applied bias voltage especially in depletion region at low frequencies. These changes in dielectric parameters can be attributed to the interfacial GaN cap layer, interface polarization and a continuous density distribution of interface states and their relaxation time at metal/semiconductor interface. While the values of the ε′ decrease with increasing frequencies, tan δ, Μ′ and M^″ increase with the increasing frequency. Also, the dielectric loss (ε^″) have a local maximum at about frequency of 100 kHz. It can be concluded that the interface polarization can occur more easily at low frequencies with the number of interface states located at the metal/semiconductor interface.     

Temperature and frequency dependent electrical and dielectric properties of Al/SiO2/p-Si (MOS) structure

The electrical and dielectric properties of Al/SiO₂/p-Si (MOS) structures were studied in the frequency range 10 kHz-10 MHz and in the temperature range 295-400 K. The interfacial oxide layer thickness of 320 Å between metal and semiconductor was calculated from the measurement of the oxide capacitance in the strong accumulation region. The frequency and temperature dependence of dielectric constant (ε′), dielectric loss (ε″), dielectric loss tangent (tan δ) and the ac electrical conductivity (σ_ac) are studied for Al/SiO₂/p-Si (MOS) structure. The electrical and dielectric properties of MOS structure were calculated from C-V and G-V measurements. Experimental results show that the ε′ and ε″ are found to decrease with increasing frequency while σ_ac is increased, and ε′, ε″, tan δ and σ_ac increase with increasing temperature. The values of ε′, ε″ and tan δ at 100 kHz were found to be 2.76, 0.17 and 0.06, respectively. The interfacial polarization can be more easily occurred at low frequencies, and the number of interface state density between Si/SiO₂ interface, consequently, contributes to the improvement of dielectric properties of Al/SiO₂/p-Si (MOS) structure. Also, the effects of interface state density (N_ss) and series resistance (R_s) of the sample on C-V characteristics are investigated. It was found that both capacitance C and conductance G were quite sensitive to temperature and frequency at relatively high temperatures and low frequencies, and the N_ss and R_s decreased with increasing temperature. This is behavior attributed to the thermal restructuring and reordering of the interface. The C-V and G/ω-V characteristics confirmed that the N_ss, R_s and thickness of insulator layer (δ) are important parameters that strongly influence both the electrical and dielectric parameters and conductivity in MOS structures.     

Study on the frequency dependence of electrical and dielectric characteristics of Au/SnO2/n-Si (MIS) structures

In this paper, we present a detailed investigation of the electrical and dielectric properties of the Au/SnO₂/n-Si (MIS) structures. The capacitance-voltage (C-V) and conductance-voltage (G/ω-V) characteristics have been measured in the frequency range of 1 kHz-1 MHz at room temperature. Calculation of the dielectric constant (?′), dielectric loss (?″), loss tangent (tan δ), ac electrical conductivity (σ_ac), ac resistivity (ρ_ac) and the electric modulus are given in the studied frequency ranges. Experimental results show that the values of dielectric parameters are a strong function of frequency. The decrease of ?′ and ?″ with increasing frequency were observed. In addition the increase of σ_ac with increasing frequency is founded. Also, electric modulus formalism has been analyzed to obtain the experimental dielectric data. The interfacial polarization can be more easily occurred at the lower frequency and/or with the number of interface state density between SnO₂/Si interface, consequently, contribute to the improvement of dielectric properties of MIS structure.     

Frequency and voltage effects on the dielectric properties and electrical conductivity of Al-TiW-Pd2Si/n-Si structures

Different from conventional metal-Si compounds-n-Si structures, the thin film of TiW alloy was deposited on Pd₂Si-n-Si to form a diffusion barrier between aluminum (Al) and Pd₂Si-n-Si. Dielectric properties and electrical conductivity of TiW-Pd₂Si/n-Si structures in the frequency range of 5 kHz-10 MHz and voltage range of (−4 V) to (10 V) have been investigated in detail by using experimental C-V and G-V measurements. Experimental results indicate that the values of ε′ show a steep decrease with increasing frequency for each voltage. On the other hand, the values of ε″ show a peak, and its intensity increases with decreasing voltage and shifts towards the lower frequency side. The ac electrical conductivity (σ_ac) and the real part of electric modulus (M′) increase with increasing frequency. Also, the imaginary part of electric modulus (M″) shows a peak and the peak position shifts to higher frequency with increasing applied voltage. It can be concluded that the interfacial polarization can be more easily occurred at low frequencies, and the majority of interface states at metal semiconductor interface, consequently contributes to deviation of dielectric properties of TiW-Pd₂Si/n-Si structures.     

Frequency and temperature dependent dielectric properties of Al/Si3N4/p-Si(1 0 0) MIS structure

The dielectric properties of Al/Si₃N₄/p-Si(1 0 0) MIS structure were studied from the C-V and G-V measurements in the frequency range of 1 kHz to 1 MHz and temperature range of 80-300 K. Experimental results shows that the ε′ and ε″ are found to decrease with increasing frequency while the value of ε′ and ε″ increase with increasing temperature, especially, above 160 K. As typical values, the dielectric constant ε′ and dielectric loss ε″ have the values of 7.49, 1.03 at 1 kHz, and only 0.9, 0.02 at 1 MHz, respectively. The ac electrical conductivity (σ_ac) increases with both increasing frequency and temperature. The activation energy of 24 meV was calculated from Arrhenius plot at 1 MHz. The results indicate that the interfacial polarization can be more easily occurred at low frequencies and high temperatures.     

Frequency and gate voltage effects on the dielectric properties of Au/SiO2/n-Si structures

To determine the dielectric constant (ε′), dielectric loss (ε″), loss tangent (tan δ), the ac electrical conductivity (σ_ac) and the electric modulus of Au/SiO₂/n-Si structure, the measurement admittance technique was used. Experimental results show that the values of ε′, ε″, tan δ, σ_ac and the electric modulus show fairly large frequency and gate bias dispersion especially at low frequencies due to the interface charges and polarization. An increase in the values of the ε′ and ε″ were observed with both a decrease in frequency and an increase in frequency. The σ_ac is found to increase with both increasing frequency and voltage. In addition, the experimental dielectrical data have been analyzed considering electric modulus formalism. It can be concluded that the interface charges and interfacial polarization have strong influence on the dielectric properties of metal-insulator-semiconductor (MIS) structures especially at low frequencies and both in depletion and accumulation regions.     

Temperature dependent electrical and dielectric properties of Sn/p-Si metal-semiconductor (MS) structures

In this study, we investigated temperature dependent electrical and dielectric properties of the Sn/p-Si metal-semiconductor (MS) structures using capacitance-voltage (C-V) and conductance-voltage (G/ω-V) characteristics in the temperature range 80-400 K. The dielectric constant (ε′), dielectric loss (ε′′), dielectric loss tangent (tan δ) and ac electrical conductivity (σ_ac) were calculated from the C-V and G/ω-V measurements and plotted as a function of temperature. The values of the ε′, ε′′, tan δ and σ_ac at low temperature (=80 K) were found to be 0.57, 0.37, 0.56 and 1.04 × 10⁻⁷, where as the values of the ε′, ε′′, tan δ and σ_ac at high temperature (=400 K) were found to be 0.75, 0.44, 0.59 and 1.21 × 10⁻⁶, respectively. An increase in the values of the ε′, ε′′, tan δ and σ_ac where observed with increase in temperature. Furthermore, the effects of interface state density (N_SS) and series resistance (R_S) on C-V characteristics were investigated in the wide temperature range.     

Dielectric properties and ac electrical conductivity studies of MIS type Schottky diodes at high temperatures

Dielectric properties and ac electrical conductivity of the Al/SiO₂/p-Si (MIS) Schottky diodes were studied in the frequency and temperature range of 10 kHz-1 MHz and 300-400 K, respectively. Experimental results show that the dielectric constant (ε′), dielectric loss (ε″), loss tangent (tan δ), ac electrical conductivity (σ_ac) and the electric modulus were found a strong function of frequency and temperature. The values of the ε′, ε″ and tan δ decrease with increasing frequencies due to the interface states capacitance and a decrease in conductance with increasing frequency. Also, these values increase with increasing temperature. The σ_ac is found to increase with increasing frequency and increasing temperature. The variation of conductivity as a function of temperature and frequency reveals non-adiabatic hopping of charge carriers between impurities localized states. In addition, the experimental dielectric data have been analyzed by considering electric modulus formalism.     

Dielectric properties in Au/SnO2/n-Si (MOS) structures irradiated under Co-γ rays

The metal-oxide-semiconductor (MOS) structures with insulator layer thickness range of 55-430 Å were stressed with a bias of 0 V during ⁶⁰Co-γ ray source irradiation with the dose rate of 2.12 kGy/h and the total dose range was 0-5×10⁵ Gy. The real part of dielectric constant ε′, dielectric loss ε″, dielectric loss tangent tanδ and the dc conductivity σ_dc were determined from against frequency, applied voltage, dose rate and thickness of insulator layer at room temperature for Au/SnO₂/n-Si (MOS) structures from C-V capacitance and G-V conductance measurements in depletion and weak inversion before and after irradiation. The dielectric properties of MOS structures have been found to be strongly influenced by the presence of dominant radiation-induced defects. The frequency, applied voltage, dose rate and thickness dependence of ε′, ε″, tanδ and σ_dc are studied in the frequency (500 Hz-10 MHz), applied voltage (−10 to 10 V), dose rate (0-500 kGy) and thickness of insulator layer (55-430 Å) range, respectively. In general, dielectric constant ε′, dielectric loss ε″ and dielectric loss tangent are found to decrease with increasing the frequency while σ_dc is increased. Experimental results shows that the interfacial polarization can be more easily occurred at the lower frequency and/or with the number of density of interface states between Si/SnO₂ interfaces, consequently, contribute to the improvement of dielectric properties of Au/SnO₂/n-Si (MOS) structures.     

On the profile of frequency dependent series resistance and dielectric constant in MIS structure

In this study, the frequency dependent of the forward and reverse bias capacitance-voltage (C-V) and conductance-voltage (G/ω - V) measurements of Al/SiO₂/p-Si (MIS) structures are carried out in frequency range of 10 kHz-10 MHz. The frequency dependence of series resistance (R_s), density of surface states (N_ss), dielectric constant (ε′), dielectric loss (ε″), dielectric loss tangent (tan δ) and the ac electrical conductivity (σ_dc) are studied for these structure at room temperature. Experimental results show that both electrical and dielectric parameters were strongly frequency and voltage dependent. The ε′ and ε″ are found to decrease with increasing frequency while σ_ac is increased. Also, both the effects of surface states N_ss and R_s on C-V and G/ω - V characteristics are investigated. It has been seen that the measured C and G decrease with increasing frequency due to a continuous distribution of N_ss in frequency range of 10 kHz-1 MHz. The effect of R_s on the C and G are found noticeable at high frequencies. Therefore, the high frequencies C and G values measured under both reverse and forward bias were corrected for the effect of series resistance R_s to obtain real MIS capacitance C_c and conductance G_c using the Nicollian and Goetzberger technique. The distribution profile of R_s-V gives a peak in the depletion region at low frequencies and disappears with increasing frequencies.     

Dielectric spectroscopy studies on (PVP + PVA) polyblend film

The thermal behavior of (PVP + PVA) polyblend film have been examined using differential scanning calorimetry and scanning electron microscopy. Capacitance and loss tangent values of polyvinyl pyrrolidone (PVP) + polyvinyl alcohol (PVA) polyblend film were measured in the frequency range 1-100 kHz and temperature range 298-423 K. Dielectric permittivity of real part (ε′) was obtained from capacitance data and dielectric permittivity of imaginary part (ε″) was obtained from real part of dielectric permittivity and loss tangent values. The decrease in dielectric permittivity was observed with increasing frequency and also observed increase in dielectric permittivity with increasing temperature. The complex dielectric constant (ε*) has been described by the electric modulus M* = (1/ε*) = M′ + iM″. The data of M* has been analysed by the stretched exponential decay of the electric field, Φ(t) = exp−(t/τ₀)^β.     

Analysis of electrical characteristics of Au/SiO2/n-Si (MOS) capacitors using the high-low frequency capacitance and conductance methods

The purpose of this paper is to analyze electrical characteristics in Au/SiO₂/n-Si (MOS) capacitors by using the high-low frequency (C_HF-C_LF) capacitance and conductance methods. The capacitance-voltage (C-V) and conductance-voltage (G/ω-V) measurements have been carried out in the frequency range of 1 kHz-10 MHz and bias voltage range of (−12 V) to (12 V) at room temperature. It was found that both C and G/ω of the MOS capacitor were quite sensitive to frequency at relatively low frequencies, and decrease with increasing frequency. The increase in capacitance especially at low frequencies is resulting from the presence of interface states at Si/SiO₂ interface. Therefore, the interfacial states can more easily follow an ac signal at low frequencies, consequently, which contributes to the improvement of electrical properties of MOS capacitor. The interface states density (N_ss) have been determined by taking into account the surface potential as a function of applied bias. The energy density distribution profile of N_ss was obtained from C_HF-C_LF capacitance method and gives a peak at about the mid-gap of Si. In addition, the high frequency (1 MHz) capacitance and conductance values measured under both reverse and forward bias have been corrected for the effect of series resistance (R_s) to obtain the real capacitance of MOS capacitors. The frequency dependent C-V and G/ω-V characteristics confirm that the N_ss and R_s of the MOS capacitors are important parameters that strongly influence the electrical properties of MOS capacitors.     

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.     

On the profile of frequency and voltage dependent interface states and series resistance in (Ni/Au)/Al0.22Ga0.78N/AlN/GaN heterostructures by using current-voltage (I-V) and admittance spectroscopy methods

In order to explain the experimental effect of interface states (N_ss) and series resistance (R_s) of device on the non-ideal electrical characteristics, current-voltage (I-V), capacitance-voltage (C-V) and conductance-voltage (G/ω-V) characteristics of (Ni/Au)/Al_0.22Ga_0.78N/AlN/GaN heterostructures were investigated at room temperature. Admittance measurements (C-V and G/ω-V) were carried out in frequency and bias voltage ranges of 2 kHz-2 MHz and (−5 V)-(+5 V), respectively. The voltage dependent R_s profile was determined from the I-V data. The increasing capacitance behavior with the decreasing frequency at low frequencies is a proof of the presence of interface states at metal/semiconductor (M/S) interface. At various bias voltages, the ac electrical conductivity (σ_ac) is independent from frequencies up to 100 kHz, and above this frequency value it increases with the increasing frequency for each bias voltage. In addition, the high-frequency capacitance (C_m) and conductance (G_m/ω) values measured under forward and reverse bias were corrected to minimize the effects of series resistance. The results indicate that the interfacial polarization can more easily occur at low frequencies. The distribution of N_ss and R_s is confirmed to have significant effect on non-ideal I-V, C-V and G/ω-V characteristics of (Ni/Au)/Al_0.22Ga_0.78N/AlN/GaN heterostructures.     

Controlling the electrical characteristics of Au/n-Si structures by interfacial insulator layer

Admittance (C–V and G/ω–V) measurements of Au/n-Si (metal–semiconductor, MS) and Au/SnO₂/n-Si (metal–insulator–semiconductor, MIS) structures were carried out between 1 kHz and 1 MHz at room temperature to investigate the interfacial insulator layer effect on the electrical characteristics of Au/n-Si structures. Experimental results showed that MIS structure's capacitance (C) values, unlike those of MS structure, became stable especially at high frequencies in the accumulation region. Also, the insulator layer caused structure's shunt resistance (R_sh) to increase. It was found that series resistance (R_s) is more effective in the accumulation region at high frequencies after the correction was applied to C and G/ω data to eliminate the R_s effect. The density of interface states (D_is) was obtained using Hill–Coleman method, D_is values MIS structure was obtained smaller than those of MS structure. Results indicate that interfacial insulator layer brings about some improvements in electrical characteristics of Au/n-Si structures.     

Annealing temperature effect on electrical and structural properties of Cu/Au Schottky contacts to n-type GaN

Schottky contacts were fabricated on n-type GaN using a Cu/Au metallization scheme, and the electrical and structural properties have been investigated as a function of annealing temperature by current-voltage (I-V), capacitance-voltage (C-V), Auger electron spectroscopy (AES) and X-ray diffraction (XRD) measurements. The extracted Schottky barrier height of the as-deposited contact was found to be 0.69 eV (I-V) and 0.77 eV (C-V), respectively. However, the Schottky barrier height of the Cu/Au contact slightly increases to 0.77 eV (I-V) and 1.18 eV (C-V) when the contact was annealed at 300 °C for 1 min. It is shown that the Schottky barrier height decreases to 0.73 eV (I-V) and 0.99 eV (C-V), 0.56 eV (I-V) and 0.87 eV (C-V) after annealing at 400 °C and 500 °C for 1 min in N₂ atmosphere. Norde method was also used to extract the barrier height of Cu/Au contacts and the values are 0.69 eV for the as-deposited, 0.76 eV at 300 °C, 0.71 eV at 400 °C and 0.56 eV at 500 °C which are in good agreement with those obtained by the I-V method. Based on Auger electron spectroscopy and X-ray diffraction results, the formation of nitride phases at the Cu/Au/n-GaN interface could be the reason for the degradation of Schottky barrier height upon annealing at 500 °C.     

Electrical and interface state density properties of the 4H-nSiC/[6,6]-phenyl C61-butyric acid methyl ester/Au diode

The electrical and interface state density properties of the Ni/4H-nSiC/PCBM/Au diode have been investigated by current-voltage, capacitance-voltage and conductance-frequency methods. The ideality factor, barrier height and series resistance values of the diode were found to be 2.28, 1.10 eV and 3.76 × 10⁴ Ω, respectively. The diode shows a non-ideal I-V behaviour with an ideality factor greater than unity that could be ascribed to the interfacial layer, interface states and series resistance. The obtained barrier height (1.10 eV) of the Ni/4H-nSiC/PCBM/Au diode is lower than that of Ni/4H-nSiC diode (1.32 eV). This indicates that the PCBM organic layer induces a change of 160 meV in the barrier height of the Ni/4H-nSiC diode. The interface state density of the diode was determined from G_p/ω-f plots and was of order of 5.61 × 10¹² eV⁻¹ cm⁻².     

Interface control and photovoltaic properties of n-type silicon/metal junction by organic dye

The electronic parameters and photovoltaic properties of the Au/methylene blue/n-Si diodes were investigated by current-voltage and capacitance-conductance-frequency techniques. The diode exhibits a non-ideal behavior due the series resistance, organic layer and oxide layer. The barrier height (1.04 eV) of the Au/methylene blue/n-Si is higher than that of Au/n-Si Schottky diode (0.83 eV) due to an excess barrier formed by organic layer. The interface state density of the diode was determined using a conductance technique and was found to be 3.25 × 10¹² eV⁻¹ cm⁻². The diode shows a photovoltaic behavior with a maximum open circuit voltage V_oc of 0.23 V and short-circuit current I_sc of 20.8 μA under 100 mW/cm². It is evaluated that Au/methylene blue/n-Si is an organic-on-inorganic photodiode with the obtained electronic parameters and methylene blue organic dye controls the interface and electrical properties of conventional metal/n-type silicon junction.     

Current transport mechanisms and deep level transient spectroscopy of Au/n-Si Schottky barrier diodes

The temperature-dependent electrical characteristics of the Au/n-Si Schottky diodes have been studied in the temperature range of 40-300 K. Current density-voltage (J-V) characteristics of these diodes have been analyzed on the basis of thermionic emission theory with Gaussian distribution model of barrier height. The basic diode parameters such as rectification ratio, ideality factor and barrier height were extracted. Under a reverse bias, the conduction process at low voltage is determined by Schottky emission over a potential barrier but at higher voltage the Poole Frenkel effect is observed. The capacitance-voltage (C-V) features of the Au/n-Si Schottky diodes were characterized in the high frequency of 1 MHz. The barrier heights values obtained from the J-V and C-V characteristics have been compared. It has been seen that the barrier height value obtained from the C-V measurements is higher than that obtained from the J-V measurements at various temperatures. Possible explanations for this discrepancy are presented. Deep level transient spectroscopy (DLTS) has been used to investigate deep levels in Au/n-Si. Three electron trap centers, having different emission rates and activation energies, have been observed. It is argued that the origin of these defects is of intrinsic nature. A correlation between C-V and DLTS measurements is investigated.     

Frequency and temperature dependence of the dielectric and AC electrical conductivity in (Ni/Au)/AlGaN/AlN/GaN heterostructures

The dielectric properties and AC electrical conductivity (σ_ac)of the (Ni/Au)/Al_0.22Ga_0.78N/AlN/GaN heterostructures, with and without the SiN_x passivation, have been investigated by capacitance-voltage and conductance-voltage measurements in the wide frequency (5kHz-5 MHz) and temperature (80-400 K) range. The experimental values of the dielectric constant (ε′), dielectric loss (ε′′), loss tangent (tanδ), σ_ac and the real and imaginary part of the electric modulus (M′ and M′′) were found to be a strong function of frequency and temperature. A decrease in the values of ε′ and ε′′ was observed, in which they both showed an increase in frequency and temperature. The values of M′ and M′′ increase with increasing frequency and temperature. The σ_ac increases with increasing frequency, while it decreases with increasing temperature. It can be concluded, therefore, that the interfacial polarization can occur more easily at low frequencies and temperatures with the number of interface states density located at the metal/semiconductor interface. It contributes to the ε′ and σ_ac.