In
semiconductor physics, the
photo–Dember effect (named after its discoverer ) is the formation of a charge
dipole in the vicinity of a
semiconductor surface after ultra-fast photo-generation of
charge carriers. The
dipole forms owing to the difference of
mobilities (or
diffusion constants) for
holes and
electrons which combined with the break of symmetry provided by the surface lead to an effective charge separation in the direction perpendicular to the surface. In an isolated sample, where the macroscopic flow of an electric current is prohibited, the fast carriers (often the electrons) are slowed down and the slow carriers (often the holes) are accelerated by an electric field, called the Dember field.