Impact of illumination level and oxide parameters on Shockley–Read–Hall recombination at the Si-SiO2 interface

Abstract

The experimentally observed dependence of effective surface recombination velocity Seff at the Si-SiO2 interface on light-induced minority carrier excess concentration is compared with theoretical predictions of an ‘‘extended Shockley–Read–Hall (SRH) formalism.’’ The calculations of SRH-recombination rates at the Si-SiO2 interface are based on the theory of a surface space charge layer under nonequilibrium conditions and take into account the impact of illumination level, gate metal work function, fixed oxide charge density, and the energy dependence of capture cross sections σn, σp and interface state density Dit. Applying this theory to p-type silicon surfaces covered by high quality thermal oxides, the experimentally observed strong increase of Seff with decreasing minority carrier excess concentration could quantitatively be attributed to the combined effect of the σn/σp ratio of about 1000 at midgap and the presence of a positive fixed oxide charge density Qf of about 1×1011 charges/cm2. Due to the favorable work function of aluminum, surface recombination velocities below 1 cm/s can be obtained at Al-covered Si-SiO2 interfaces for minority carrier densities above 1013 cm−3.