The investigation of temperature dependence current-conduction mechanism and electrical characteristics of Al/SiO2/p-Si (MIS) stuctures

The current-voltage (I-V), capacitance-voltage (C-V) and conductance-voltage (G/w-V) characteristics of Al/SiO2/p-Si metal-insulator-semiconductor (MIS) structure/ Schottky diodes were measured in the temperature range of 80-400 K. The calculated zero bias barrier height ( ? Bo) and the ideality factor (n) values according to thermionic emission (TE) theory show strong temperature dependence. While ? Bo increases, n decreases with increasing temperature. The activation energy obtained from Richardson plot deviated from linearity under room temperatures. Such behaviour is attributed to inhomogeneties of Schottky barrier by assuming a Gaussian distribution (GD) of barrier heights (BHs) at Al/p-Si interface. We attempted to draw a ? Bo vs q/2kT plot to obtain evidence of a Gaussian distribution of the BHs and the values of = 1.136 eV and ? o= 0.159 V for the mean BH and standard deviation at zero bias, respectively, have been obtained from this plot. Thus, the modified [ln(Io/T2)-q2 ? o2/2k2T2] vs q/kT plot gives and A* as 1.138 eV and 37.23 Acm-2K-2, respectively. This value is very close to the theoretical value of 32 A K-2 cm-2 for p-type Si. Hence, it has been concluded that the temperature dependence of the forward I-V characteristics of the Al/SiO2/p-Si structure can be successfully explained on the basis of TE mechanism with a GD of the BHs. The forward and reverse bias C-V and G/w-V characteristics of Al/SiO2/p-Si MIS Schottky diodes have been investigated by considering the effect of the series resistance (Rs) and surface states (Nss) over a wide temperature and the voltage range of 80-400 K and ? 8 V, respectively, at 1 MHz. It is found that in the presence of series resistance, the forward bias C-V plots exhibits a peak, and experimentally shown that the peak positions shift towards higher positive potentials with increasing temperature. The C-V and G/w-V characteristics confirm that the Nss and Rs of the diode are important parameters that strongly influence the electrical parameters in (Al/SiO2/p-Si) MIS Schottky diodes. The crossing of the G/w-V curves appears as an abnormality when seen respect to the behavior of ideal MIS Schottky diode. In addition, the high frequency C and G/w values measured under both reverse and forward bias were corrected for the effect of series resistance to obtain the real diode capacitance.