  In this work the influence of the electric and magnetic fields over a
tunneling particle in a rectangular potential barrier is shown, we have taken
into account the presence of an impurity at the barrier center and the effects
of a hydrostatic pressure parallel to the barrier height considering the
BenDaniel-Duke boundary conditions. Given that the particle is moving inside a
GaAs-AlxGa1-xAs-GaAs heterostructures it is evident a change in the
transmission coefficient due to the impurity concentration and the presence of
the hydrostatic pressure. The potential due to the presence of the impurity is
approximate with a second degree polynomial function that resolves the
discontinuity generated by heavily modifying the transmission coefficient.
