Effects of Certain Chemical Treatments and Ambient Atmospheres on Surface Properties of Silicon

Abstract

Measurements of surface conductance, recombination velocity (S), and field effect were made on n‐ and p‐type silicon specimens with certain surface treatments and ambient atmospheres. The conditions covered a wide range in surface potential (0.7 ev) and recombination velocity (40‐104 cm/sec). Low recombination velocity occurred when the surface was strongly p‐type, after treatments in boiling deionized water or sodium dichromate solution, or when the surface was strongly n‐type, after treatment in concentrated hydrofluoric acid. Atmospheres which bend the energy bands back toward the middle from these extreme conditions caused S to increase. Curves of S vs. band position at the surface for the various treatments appear to be branches of the type of curve predicted by theory for recombination centers at a discrete energy level. The position of the Fermi level at the surface for a given treatment apparently depended to a small extent on whether the bulk material was n‐ or p‐type. This apparent difference, which is contrary to experience on germanium, may have been caused in part by poor contact between an inversion layer and the bulk material.