Frequency and voltage-dependent dielectric properties and AC electrical conductivity of (Au/Ti)/Al₂O₃/n-GaAs with thin Al₂O₃ interfacial layer at room temperature

An (Au/Ti)/Al₂O₃/n-GaAs structure with thin (30 Å) interfacial oxide layer (Al₂O₃), formed by atomic layer deposition technique 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 tanδ and ac electrical conductivity σ_{AC} in a wide frequency range from 1000 Hz to 1 MHz at room temperature. The dielectric properties of the (Au/Ti)/Al₂O₃/n-GaAs metal-insulator-semiconductor structure 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 from -4 V to +4 V, at room temperature. Experimental results show that the dielectric parameters were strongly frequency and voltage dependent. For each frequency the (C-V) plots show a peak and the change in frequency has effect on both the intensity and position of the peak. ε', ε'' and tanδ decrease with increasing frequency, whereas σ_{AC} increases with increasing frequency at applied bias voltage. M' increases with the increasing frequency and reaches a maximum. M'' shows a peak and peak position shifts to higher frequency with increasing applied voltage. It can be concluded that the ε', ε'', tanδ, M', M'' and σ_{AC} values of the (Au/Ti)/Al₂O₃/ n-GaAs structure are strongly dependent on both the frequency and applied bias voltage especially in the depletion and accumulation region. Also, the results can be deduced to imply that the interfacial polarization is easier at low frequencies, therefore contributing to the deviation of dielectric properties and AC electrical conductivity of (Au/Ti)/Al₂O₃/n-GaAs structure.