Guilin Sun
Ansys Employee

Surface recombination can be defined as the product of surface recombination velocity and the difference in minority carrier concentrations between thermal equilibrium and at the surface, and surface recombination velocity depends on some intrinsic material parameters, such as the minority carrier diffusion length (Fitzgerald and Grove, 1968).

In addiiton, the surface recombination velocity is also dependent on the surface roughness, contamination and defects.

That said, if you have a perfect, ideal semiconductor surface, this velocity is very small, if not zero. In most cases, such recombination only has effect of about a few percent at most. Other parameters may have larger effect. My personal suggestion is, simply use a value and try the result. You can also compare results with different values.

With the above information, together with what you can find online search, probably other questions are not questions.