We give an example of supersonic solutions to a one-dimensional steady state Euler-Poisson system arising in the modeling of plasmas and semiconductors. The existence of the supersonic solutions which correspond to large current density is proved by Schauder's fixed point theorem. We show also the uniqueness of solutions in the supersonic region. Keywords. Euler-Poisson equations, steady state flow, supersonic solutions, existence, uniqueness. 2000 Mathematics Subject Classification. 35J25, 35Q35, 76J20.