The classical time-dependent drift-diffusion model for semiconductors is considered for small
scaled Debye length (which is a singular perturbation parameter). The corresponding limit is
carried out on both the dielectric relaxation time scale and the diffusion time scale. The latter
is a quasineutral limit, and the former can be interpreted as an initial time layer problem.
The main mathematical tool for the analytically rigorous singular perturbation theory of this
paper is the (physical) entropy of the system.