It is well known that the recombination of excess carriers at semiconductor surfaces can be substantially reduced by electrostatic charge. The ability to incorporate large charge densities in dielectric films, and to vary the charge density through adjustment of deposition parameters or post deposition treatments, raises an important practical question: how much charge is enough for optimum passivation? We attempt to answer this question through direct measurement of the emitter saturation

more »

... nt density Joe as a function of applied voltage on samples with a symmetric metal-insulator-semiconductor (MIS) structure. Our results indicate that the impact of applied charge density on surface recombination tends to saturate at charge densities of around 8x10-7C/cm-2 (5x1012 charges cm-2), so that higher charge densities do not offer any increased benefit for surface passivation. While our results are currently confined chiefly to oxide passivated samples, we expect that a similar behavior will be observed for samples passivated with other dielectric films.