Surface States in Tunnelable MOS Structures

Abstract

The bias dependence of the tunneling current, low frequency capacitance and differential conductance of MOS structures with very thin SiO2 films on p-type Si substrates have been investigated over the temperature range from 151 K to 324 K. The surface state density of about ∼8×1011 states/cm2 is obtained for p–Si(100) orientation and of a little higher value for p–Si(111), but the energy distribution of surface states near the valuence band depends strongly on the crystallographic orientation. The surface state capture cross-sections for p–Si(111) and p–Si (100) MOS are 2.0×10-16 cm2 and 3.1×10-16 cm2, respectively. Experimental evidence of the tunneling current component from metal to surface states is seen in DC conductance and surface state density measurements.