Dielectric spectroscopy studies and ac electrical conductivity on (AuZn)/TiO2/p-GaAs(110) MIS structures

In this study, we investigated temperature and voltage dependence of dielectric properties and ac electrical conductivity (sigma(ac)) of (AuZn)/TiO2/p-GaAs(110) metal-insulator-semiconductor structures in the temperature range of 80-290 K using the capacitance-voltage (C - V) and conductance-voltage (G/omega - V) measurements at 1 MHz. The intersection/crossing behaviour of C-V plots at sufficiently high forward biases and the increase in sigma(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 (epsilon'), dielectric loss (epsilon ''), loss tangentdtan (tan delta), ac electrical conductivity (sigma(ac)), the real and imaginary parts of electric modulus (M', M '') were found to be strong functions of temperature and applied bias voltage. The Cole-Cole plots between M' vs: M '' 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 '' vs. V plot has a peak for each temperature. The Ln (sigma(ac)) 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.