Native defects at the Si/SiO2 interface?amorphous silicon revisited

Abstract

We review here work which demonstrates that silicon dangling bonds, Si3, are the predominant, electrically active deep states associated with the clean crystalline silicon/amorphous SiO2 interface. Si3 exists in three charge states in the silicon band gap with E+,0 ⋍ Ev + 0.3 eV and E0,− ⋍ Ev + 0.9 eV, where E represents a demarcation level between charge states. We discuss the structural and electronic characteristics of Si3 at the Si/SiO2 interface, including degree of charge localization, effective correlation energies, role of hydrogen passivation, etc. We argue, from the strongly analogous behavior in amorphous silicon, that the electronic density of states in the gap is dominated by the characteristic effects of disorder in covalently bonded semiconductors. The states consist of two topologically distinct entities: distorted, fully-bonded network configurations giving rise to shallow silicon band tails, and three-fold coordinated, amphoteric silicon defects.