In this article we propose a rapid method to compute the steady states, including bifurcation diagrams, of resonant tunneling heterostructures in the far from equilibrium regime. Those calculations are made on a simplified model which takes into account the characteristic quantities which arise from an accurate asymptotic analysis of the nonlinear Schrödinger-Poisson system. After a summary of the former theoretical results, the asymptotical model is explicitly adapted to physically realistic situations and numerical results are shown in various cases.MSC : 34L25, 34L30, 34L40, 65L10, 65Z05, 82D37