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.     

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.     

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.     

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 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.     

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 dependent dielectric studies of Ni/n-GaP Schottky diodes by capacitance and conductance measurements

The dielectric properties of Ni/n-GaP Schottky diode were investigated in the temperature range 140–300 K by capacitance–voltage (C–V) and conductance–voltage (G/ω–V) measurements. The effect of temperature on series resistance (R_s) and interface state density (N_ss) were investigated. The dependency of dielectric constant (ε′), dielectric loss (ε′′), loss tangent (tan δ), ac conductivity (σ_ac), real (M′) and imaginary (M′′) parts of the electric modulus over temperature were evaluated and analyzed at 1 MHz frequency. The temperature dependent characteristics of ε′ and ε′′ reveal the contribution of various polarization effects, which increases with temperature. The Arrhenius plot of σ_ac shows two activation energies revealing the presence of two distinct trap states in the chosen temperature range. Moreover, the capacitance–frequency (C–f) measurement over 1 kHz to 1 MHz was carried out to study the effect of localized interface states.     

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.     

Temperature dependent electrical and dielectric properties of Au/polyvinyl alcohol (Ni, Zn-doped)/n-Si Schottky diodes

The electrical and dielectric properties of Au/PVA (Ni, Zn-doped)/n-Si Schottky diodes (SDs) were studied in the temperature range of 80-400 K. The investigation of various SDs fabricated with different types of interfacial layer is important for understanding the electrical and dielectric properties of SDs. Therefore, in this study polyvinyl alcohol (PVA) film was used as an interfacial layer between metal and semiconductor. The electrical and dielectric properties of Au/PVA (Ni, Zn-doped)/n-Si SDs were calculated from the capacitance-voltage (C-V) and conductance-voltage (G/w-V) measurements. The effects of interface state density (N_ss) and series resistance (R_s) on C-V characteristics were investigated in the wide temperature range. It was found that both of the C-V-T and G/w-V-T curves included two abnormal regions and one intersection point. The dielectric constant (ε″), dielectric loss (ε″), dielectric loss tangent (tan δ) and the ac electrical conductivity (σ_ac) obtained from the measured capacitance and conductance were studied for Au/PVA (Ni, Zn-doped)/n-Si SDs. Experimental results show that the values of ε′, ε″ and tan δ are a strong function of the temperature. Also, the results indicate the interfacial polarization can be more easily occurred at high temperatures.     

Electrical and dielectric properties of chromotrope 2R in pellet and thin film forms

The dark conductivity (dc and ac) and dielectric properties of chromotrope 2R (CHR) in pellet as well as in thin film forms have been investigated as function of frequency (100 Hz to 5 MHz) within the temperature range (293–423 K). The ac conductivity of CHR pellet in sandwich structure employing two symmetrical gold ohmic contacts shows both temperature and frequency dependence with relatively stronger dependence in the higher temperature and lower frequency ranges respectively. It is found that σ_ac(ω) obey Jonscher’s universal power law, σ_ac(ω) = Aω^s with s < 1 and the results has been analyzed with reference to various theoretical models. The correlated barrier hopping model (CBH) with single polaron process is found to be the dominant conduction mechanism for charge carrier transport in CHR material within the investigated temperature range. The dc conductivity has been measured in the considered temperature range for as deposited and annealed films. The results are fitted to Arhenius equation and the activation energy has been deduced at different frequencies. The results showed also that heating the deposited CHR films may reveal films with more stable electrical properties. Moreover, both the dielectric constant ε₁ and the dielectric loss ε₂ are found to increase with temperature and decrease with frequency which reveal that the CHR samples exists in molecular dipole form. The behavior of ε₂ as a function of both frequency and temperature is analyzed according to Giuntini et al. model.     

Electrical properties of zinc oxide sputtered thin films

ZnO thin films were deposited on silicon substrate by rf magnetron sputtering from metallic zinc target. The electrical properties of ZnO are currently being studied. In this work, measurements of the ac conductivity properties of ZnO sandwich structures with silver and platinum electrodes are reported. The frequency dependence of both the ac conductivity and dielectric constant of thin films of ZnO have been investigated in the frequency range 5 kHz-13 MHz. It is shown that the total ac conductivity σ(ω), obeys the equation σ(ω)=Aω^S where s is an index which increases with frequency and decreases with temperature. It appears that for ZnO films, the conduction mechanism is thermally activated and both the overlap large polaron tunnelling and the correlated barrier-hopping of charge carrier over localized states fit the experimental data. The dielectric constant, ε_r, lies in the range 8-9 at room temperature and is independent of the frequency in the dielectric thin films.     

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 characteristics of gamma irradiated Au/SnO2/n-Si/Au (MOS) capacitor

The dielectric characteristics of gamma irradiated Au/SnO₂/n-Si/Au (MOS) capacitor were studied. The MOS capacitor was irradiated by a ⁶⁰Co gamma radiation source with a dose rate of 0.69 kGy/h. The dielectric parameters such as dielectric constant (ε′), dielectric loss (ε″), loss factor (tan δ) and ac electrical conductivity (σ_ac) were calculated from the capacitance–voltage (C–V) and conductance–voltage (G/ω–V) measurements. It is found that the C and G/ω values decrease with the increasing total dose due to the irradiation-induced defects at the interface. Also, the calculated values of ε′, ε″ and σ_ac are found to decrease with an increased radiation dose. This result indicates that the dielectric characteristics of the MOS capacitor are sensitive to gamma-ray dose.     

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.     

Dielectric Properties of Au/PVA (Cobalt-Doped)/n-Si Photoconductive Diodes

The voltage (V) and frequency (f) dependence of dielectric parameters such as the dielectric constant (ε′), dielectric loss (ε″), dielectric loss tangent (tan δ), real and imaginary parts of electrical modulus (M′ and M″), and alternating-current (AC) electrical conductivity (σ _AC) of Au/PVA (cobalt-doped)/n-Si structures have been investigated by using experimental admittance measurements conducted at room temperature. The values of ε′, ε″, and tan δ were found to be strong functions of voltage and frequency, especially at low frequencies in the positive voltage region. It was observed that the values of ε′ and ε″ increase as the frequency decreases. The M′ values increase with increasing frequency due to increasing dielectric relaxation, while M″ values, in general, remain stable as frequency is changed. The σ _AC values at each bias voltage increase with increasing frequency.     

HfAlOx high-k gate dielectric on SiGe: Interfacial reaction, energy-band alignment, and charge trapping properties

Ultra thin HfAlO_x high-k gate dielectric has been deposited directly on Si_1−xGe_x by RF sputter deposition. The interfacial chemical structure and energy-band discontinuities were studied by using X-ray photoelectron spectroscopy (XPS), time of flight secondary ion mass spectroscopy (TOF-SIMS) and electrical measurements. It is found that the sputtered deposited HfAlO_x gate dielectric on SiGe exhibits excellent electrical properties with low interface state density, hysteresis voltage, and frequency dispersion. The effective valence and conduction band offsets between HfAlO_x (E_g = 6.2 eV) and Si_1−xGe_x (E_g = 1.04 eV) were found to be 3.11 eV and 2.05 eV, respectively. In addition, the charge trapping properties of HfAlO_x/SiGe gate stacks were characterized by constant voltage stressing (CVS).     

High performance TaYOx-based MIM capacitors

TaYO_x-based metal-insulator-metal (MIM) capacitors with excellent electrical properties have been fabricated. Ultra-thin TaYO_x films in the thickness range of 15-30 nm (EOT ∼ 2.4-4.7 nm) were deposited on Au/SiO₂ (100 nm)/Si (100) structures by rf-magnetron co-sputtering of Ta₂O₅ and Y₂O₃ targets. TaYO_x layers were characterized by X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray (EDX) and X-ray diffraction (XRD) to examine the composition and crystallinity. An atomic percentage of Ta:Y = 58.32:41.67 was confirmed from the EDX analysis while XRD revealed an amorphous phase (up to 500 °C) during rapid thermal annealing. Besides, a high capacitance density of ∼3.7-5.4 fF/μm² at 10 kHz (ε_r ∼ 21), a low value of VCC (voltage coefficients of capacitance, α and β) have been achieved. Also, a highly stable temperature coefficient of capacitance, TCC has been obtained. Capacitance degradation phenomena in TaYO_x-based MIM capacitors under constant current stressing (CCS at 20 nA) have been studied. It is observed that degradation depends strongly on the dielectric thickness and a dielectric breakdown voltage of 3-5 MV/cm was found for TaYO_x films. The maximum energy storage density was estimated to be ∼5.69 J/cm³. Post deposition annealing (PDA) in O₂ ambient at 400 °C has been performed and further improvement in device reliability and electrical performances has been achieved.     

Materials characterization of WNxCy, WNx and WCx films for advanced barriers

A ternary WN_xC_y system was deposited in a thermal ALD (atomic layer deposition) reactor from ASM at 300 °C in a process sequence using tungsten hexafluoride (WF₆), triethyl borane (TEB) and ammonia (NH₃) as precursors. The WC_x layers were deposited by a novel ALD process at a process temperature of 250 °C. The WN_x layers were deposited at 375 °C using bis(tert-butylimido)-bis-(dimethylamido)tungsten (^tBuN)₂(Me₂N)₂W (imido-amido) and NH₃ as precursors. WN_x grows faster on plasma enhanced chemical vapor deposition (PECVD) oxide than WC_x does on chemical oxide. WN_xC_y grows better on PECVD oxide than on thermal oxide, which is opposite of what is seen for WN_x. In the case of the ternary WN_xC_y system, the scalability towards thinner layers and galvanic corrosion behavior are disadvantages for the incorporation of the layer into Cu interconnects. ALD WC_x based barriers have a low resistivity, but galvanic corrosion in a model slurry solution of 15% peroxide (H₂O₂) is a potential problem. Higher resistivity values are determined for the binary WN_x layers. WN_x shows a constant composition and density throughout the layer.