Electric Field Strength Dependence of Surface Damage in Oxde Passivated Silicon Planar Transistors

A dependence of surface degradation induced by ionizing radiation in matched oxide-passivated silicon planar epitaxial transistors on junction fringing electric field strength present during exposure is reported. The electric field strength and gamma dose dependence are investigated of the decrease in the forward current gain, hFE (as reflected by the increase in the surface recombination current component), the increase in the surface recombination velocity (as reflected by the increase in the reciprocal of the minority carrier lifetime), and the increase in junction capacitance. Empirical prediction equations have been derived, for matched devices, correlating the normalized base current increase and the normalized surface recombination velocity increase with the average junction electric field strength present during irradiation and the total gamma dose. The ionizing radiation induced surface recombination and surface channel components are analyzed from a study of the reciprocal slope term, "n", obtained from forward and inverse configuration current-voltage data.