  We study differential shot noise in mesoscopic diffusive
normal-superconducting (NS) heterostructures at finite voltages where nonlinear
effects due to the superconducting proximity effect arise. A numerical
scattering-matrix approach is adopted. Through an NS contact, we observe that
the shot noise shows a reentrant dependence on voltage due to the
superconducting proximity effect but the differential Fano factor stays
approximately constant. Furthermore, we consider differential shot noise in the
structures where an insulating barrier is formed between normal and
superconducting regions and calculate the differential Fano factor as a
function of barrier height.
