Investigation of dielectric relaxation and ac electrical conductivity using impedance spectroscopy method in (AuZn)/TiO2/p-GaAs(1 1 0) schottky barrier diodes

Abstract

Dielectric properties and ac electrical conductivity of (AuZn)/TiO2/p-GaAs(110) Schottky barrier diodes (SBDs) were investigated by using impedance spectroscopy method (capacitance and conductance measurements) in a wide frequency and applied bias voltage ranges at room temperature. The values of dielectric constant (ε′), dielectric loss (ε″), dielectric loss tangent (tanδ), real and imaginary parts of electrical modulus (M′ and M″) and ac electrical conductivity (σac) were found considerably sensitive to frequency and applied bias voltage especially in depletion and accumulation regions. While the values of ε″, ε″ and tanδ decrease, M′ and M″ increase with increasing frequencies due to the effect of interface states/traps (Nss), interfacial and dipole polarizations, series resistance (Rs) and interfacial layer. Changes in these parameters are considerably high at low frequencies and they confirmed that the interfacial and dipole polarizations can occur more easily at low frequencies. Majority of the charges at Nss between (TiO2/p-GaAs) can also easily follow external ac signal and so contributes to deviation of dielectric properties of the (AuZn)/TiO2/p-GaAs(110) SBDs. In addition, structural properties of the sample such as crystallographic quality and interface characteristics were analyzed by X-ray Diffraction (XRD) and Secondary Ion Mass Spectrometry (SIMS) measurements. Surface morphology of the sample was characterized by atomic force microscopy (AFM) measurements. Surface RMS roughness values of the sample is obtained as 8.94nm over a scan area of 3μm×3μm.