Modeling Recombination at the Si-Al2O3 Interface

In this paper, we present a complete set of data on the silicon surface passivation parameters of Al2O3 deposited by atmospheric pressure chemical vapor deposition with triethyldialuminum-tri-(sec-butoxide) and H2O precursors at temperatures between 325 and 520 degrees C. Using measured values of the total interface charge Q(tot) and of the interface defect density D-it (E), apparent electron capture cross section sigma(n)(E), and apparent hole capture cross section sigma(p)(E) as a function of the energy within the bandgap E, we calculate surface recombination velocities using the Shockley-Read-Hall (SRH) model and compare these with measured values, finding excellent agreement when Q(tot) is large and reasonable agreement otherwise. The resulting model is valid for both n- and p-type substrates, under the condition that holes are the majority carrier at the surface, as is generally the case for typical (negative) values of Q(tot). It is shown that, under these conditions, recombination is dominated by a single donor-like defect species located just below midgap. These results support the direct correspondence between Q(tot), D-it (E), sigma(n), and sigma(p) determined by capacitance and conductance measurements of metal-insulator-semiconductor structures and the carrier lifetimes measured by photoconductance.