Deactivation of silicon surface states by Al-induced acceptor states from Al-O monolayers in SiO₂

Al-O monolayers embedded in ultrathin SiO2 were shown previously to contain Al-induced acceptor states, which capture electrons from adjacent silicon wafers and generate a negative fixed charge that enables efficient Si-surface passivation. Here, we show that this surface passivation is just in part attributed to field-effect passivation, since the electrically active interface trap density D-it itself at the Si/SiO2 interface is reduced by the presence of the acceptor states. For sufficiently thin tunnel-SiO2 films between the Si-surface and the Al-O monolayers, D-it is reduced by more than one order of magnitude. This is attributed to an interface defect deactivation mechanism that involves the discharge of the singly-occupied dangling bonds (P-b0 defects) into the acceptor states, so that Shockley-Read-Hall-recombination is drastically reduced. We demonstrate that the combined electronic and field-effect passivation allows for minority carrier lifetimes in excess of 1 ms on n-type Si and that additional H-2-passivation is not able to improve that lifetime significantly. Published under license by AIP Publishing.