In this study, we investigated temperature and voltage dependence of dielectric properties and ac electrical conductivity (σ ac ) of (AuZn)/TiO 2 /p-GaAs(110) metal-insulator-semiconductor structures in the temperature range of 80-290 K using the capacitance-voltage C À V ð Þ and conductance-voltage ð G x À V Þ measurements at 1 MHz. The intersection/crossing behaviour of C-V plots at sufficiently high forward biases and the increase in σ ac with increasing temperature was attributed to the lack of sufficient number of enough free charge carriers at low temperatures. The values of the dielectric constant (ε′), dielectric loss (ε″), loss tangent tan d ð Þ, ac electrical conductivity (σ ac ), the real and imaginary parts of electric modulus (M 0 ; M 00 ) were found to be strong functions of temperature and applied bias voltage. The Cole-Cole plots between M 0 vs: M 00 have shown only one semicircle for each temperature. This indicates one of the relaxation processes was suppressed and this can be attributed to the surface polarization effect. On the other hand, M 00 vs. V plot has a peak for each temperature. The Ln r ac ð Þ vs. q kT plots revealed two linear regions with different slopes for sufficiently high forward biases (0.0, 0.5, and 1.0 V) which correspond to low (80-200 K) and moderate/intermediate (230-290 K) temperatures. Thus, the values of activation energy (E a ) were obtained from the slope of these Arrhenius plots for two linear regions as 87.3 and 3.4 meV, respectively, at 1.0 V. On the other hand, Mott plots have only one linear region except for 260 and 290 K and Mott parameters were determined from these plots at 0.0, 0.5 and 1.0 V.

An Al/SiO2/p-Si (MOS) capacitor with a thick (826 Å) interfacial oxide layer (SiO2) which is formed by using the thermal oxidation method is fabricated to investigate both frequency and applied bias voltage dependences of real and imaginary parts of dielectric constant (𝜀 ′ and 𝜀 ′′ ) and electric modulus (𝑀 ′ and 𝑀 ′′ ), loss tangent (tan 𝛿) and ac electrical conductivity (𝜎ac) in a wide frequency range from 1 kHz to 1 MHz at room temperature. The dielectric properties of the MOS capacitor are obtained using the forward and reverse bias capacitance-voltage (𝐶-𝑉 ) and conductance-voltage (𝐺/𝜔-𝑉 ) measurements in the applied bias voltage range 1.4-5.6 V. The values of 𝜀 ′ , 𝜀 ′′ , tan𝛿, 𝑀 ′ , 𝑀 ′′ and 𝜎ac are found to be strong functions of frequency and applied bias voltage in the depletion region due to excess capacitance 𝐶ex and conductance 𝐺ex/𝜔 especially at low frequencies. The experimental results show that the interfacial polarization can occur at low frequencies more easily, consequently contributing to the dispersion in 𝜀 ′ , 𝜀 ′′ , tan𝛿, 𝑀 ′ , 𝑀 ′′ and 𝜎ac values of the MOS capacitor. The other reason for dispersion in the dielectric properties may be attributed to a particular density distribution of interface states (𝑁ss) localized at the Si/SiO2 interface, as well as space charge carriers and inhomogeneity of interfacial oxide layer. The increase in conductivity with increasing frequency can be attributed to the hopping type conduction mechanism. It can be concluded that the 𝜀 ′ , 𝜀 ′′ , tan𝛿, 𝑀 ′ , 𝑀 ′′ and 𝜎ac values of the Al/SiO2/p-Si (MOS) capacitor are strongly dependent on both the frequency and applied bias voltage especially in the depletion region.

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