Direct evidence for electron injection into the conduction band during the anodic oxidation of silicon

While the role of hole capture during silicon anodic oxidation is well established, the contribution of electron injection into the conduction band remains an open question. Here, we report a dual-channel electrochemical measurement process based on a silicon p-n junction diode with a p⁺ surface layer formed on an n-type silicon (111) wafer, enabling direct probing of electron injection into the conduction band during silicon anodic oxidation. The observation of an anodic oxidation-induced short-circuit current in the diode provides a direct demonstration of electron injection into the conduction band of silicon. Quantitative analysis of the anodic current and anodic oxidation-induced short-circuit current gives an estimated electron-injection-to-hole-capture ratio on the order of 1 : 10.