Photoinjection phenomena in a silicon-silcon dioxide system

Abstract

Silicon-silicon dioxide structures obtained by thermal, anodic, and chemical oxidation of silicon are studied by the photocharge and photoinjection current methods. It is shown that the extent of the fluctuation state “tails" near the edges of the SiO2 forbidden zone is small (∼0.2 eV). The threshold for negative photocharging of anodic oxide traps is found to decrease with increase in oxide thickness, a fact related to the existence of a nonstoichiometric transition layer between the silicon and silicon dioxide. The effect of hydration and dehydration on negative optical charge of oxide traps is studied, and it is shown that the basis of electron traps is formed by the most hydrated and deformed SiO4Hn tetrahedra. The possibility of creating electron and hole traps in the oxide layer by doping with metal ions from a solution is demonstrated. It is found that the corresponding defects are also adsorption centers for water molecules by a coordination mechanism.