On the Diffusion limit of a semiconductor Boltzmann-Poisson system without micro-reversible process Nader Masmoudi 1 , Mohamed Lazhar Tayeb 2 1 Courant Institute of Mathematical Sciences, 251 Mercer Street, New York, NY 10012, USA. email: masmoudi@cims.nyu.edu 2 Facult´ e des Sciences de Tunis, Campus Universitaire El-Manar, 1060 Tunis Tunisia. email: lazhar.tayeb@fst.rnu.tn Abstract. This paper deals with the diffusion approximation of a semiconductor Boltzmann- Poisson system. The statistics of collisions we are considering here, is the Fermi-Dirac operator with the Pauli exclusion term and without the detailed balance principle. Our study generalizes, the result of Goudon and Mellet [14], to the multi-dimensional case. keywords: Semiconductor, Boltzmann-Poisson, diffusion approximation, Fermi-Dirac, detailed balance, Hybrid-Hilbert expansion, entropy dissipation. 1