Dielectric properties and ac electrical conductivity of MIS structures in the wide frequency and temperature range

Abstract

Dielectric properties and electrical conductivity of the Al/SiO2/p-Si (MIS) structures have been investigated in the temperature and frequency range of 80-400 K and 1 kHz-100 kHz, respectively. Experimental results show that the dielectric constant (ε′), dielectric loss (ε″), loss tangent (tanδ) and ac electrical conductivity (σac) were found expect 100 kHz a strong function of frequency and temperature. The dielectric constant ε′ especially shows a maximum about at 300 K, which shifts to high temperature with increasing frequency. On the other hand dielectric loss ε″ decreases with increasing both frequency and temperature, and at high temperature becomes frequency- independent. The decrease in the ε″ with increasing frequency can be understood in terms of a decrease in electrical conductivity. In addition, the experimental dielectric data have been analyzed in the light of electric modulus formalism. The values of σac conductivity show strong frequency dependence at high temperatures while at low temperatures becomes almost constant. The Lnσac vs q/kT plots show that the activation energy (Ea) decreases with increasing frequency and they are found as 65.8 meV and 56.5 meV for 1 kHz and 100 kHz, respectively. It was observed that at low temperature, the dipolar and space charge polarization process may be dominating the dielectric relaxation, while at high temperature; the thermally activated mechanism is more significant.