The investigation of frequency and temperature dependent electrical and dielectric properties in metal-insulator-semiconductor (MIS) structures

In this study, metal-insulator-semiconductor (Al/SiO2/p-Si) MIS structure withinsulator layer thick 32 Å, which growth by thermal oxidation have beenfabricated on boron doped (p-type) single crystal silicon wafer with (100)surface orientation, 280 µm thick and 8 Ω.cm resistivity. The forward andreverse bias capacitance-voltage (C-V) and conductance-voltage (G/ω-V)ωcharacteristics of these structures have been investigated taking into account theeffect of the series resistance (Rs) and surface states (Nss) over a wide frequencyand the voltage range of 10 kHz-10 MHz and (-5 V) - (+5 V), respectively, atroom temperature. Experimental results show that both electrical and dielectricparameters were strongly frequency and voltage dependent. For eachfrequency, the C-V plots show a peak and the change in frequency has effect onboth the intensity and position of the peaks. Also the distribution profile of Rs-Vplot gives a peak in the depletion region of low frequencies and disappears withincreasing frequencies. The dielectric constant (ε') and dielectric loss (ε'') arefound to decrease with increasing frequency while ac electrical conductivity(σac) is increased. The surface states can easily follow the ac signal especially atσlow frequencies and yield an excess capacitance and conductance, whichdepends on the relaxation time of Nss and frequency of the applied ac signal.In addition, dielectric properties and electrical conductivity the MIS structurewith insulator layer thick 53 Å were studied in the frequency and temperaturerange of 10 kHz-1 MHz and 300-400K, respectively. The values of ε', ε'' andtanδ were found to increases with increasing temperature and decrease withincreasing frequency. Also the electrical conductivity (σac) is found to increaseσfrequency and temperature. The activation energy values were evaluated and agood agreement between than activation energy values obtained fromconductivity measurements. In conclude that, both frequency and temperaturedependent C-V and G/ω-V characteristics confirm that the Nss and Rs of theωMIS structure are important parameters that strongly influence both theelectrical and dielectric properties of MIS structures.Key Words : MIS structures; Electrical and dielectric properties; Insulatorlayer, Surface states, Series resistance; ac electrical conductivity;electric modulus