Applicability of Shockley–Read–Hall Theory for Interface States

The Shockley–Read–Hall (SRH) model has been successfully used for decades to describe the dynamics of interface states. Interestingly, the SRH model neglects structural relaxation at the defect site, which has a dramatic effect on the dynamics of oxide defects. One may, therefore, wonder why this omission has not led to serious and obvious discrepancies with experimental data. Using
ab initio
approaches to investigate Si dangling bonds, known as
${P}_{b}$
centers, within a realistic Si/a-SiO
₂
environment together with the more complete nonradiative multiphonon (NMP) theory, we explore why the SRH model provides an excellent approximation for interface traps but not for bulk oxide defects. We will also show that the commonly used Arrhenius correction of the capture cross section can be used to introduce a modified SRH model, which provides a reasonable approximation to the results obtained from a full NMP approach. However, it is shown that this Arrhenius correction may lead to incorrect relaxation energy estimations, especially for bulk oxide defects.