RATE-EQUATION SIMULATION OF THE HEIGHT OF SCHOTTKY BARRIERS AT THE SURFACE OF OXIDIC SEMICONDUCTORS

Rate equation simulation is used in the present computational approach in order to study the role of different adsorbed oxygen ions (O2- and O-) in controlling the height of the Schottky barrier at the surface of SnO2, a key material in the field of semiconductor gas sensors. Computations are based on the adsorption/desorption model and consider the electron transfer between different oxygen species on the surface and the bulk conduction band. Different values have been tested for both the frequency factors and the activation energies of the rate constants in order to consider the relative population between the O- and O2- ions on the surface at different temperatures, the dependence of the height of the surface Schottky barrier on temperature and oxygen partial pressure, and also the response and recovery times of the barrier heights as a consequence of rapid temperature changes. Comparisons of calculated barrier heights with some empirical values are also given at different temperatures and oxygen partial pressures.