  In the paper, we consider a multi-dimensional bipolar hydrodynamic model from
semiconductor devices and plasmas. This system takes the form of Euler-Poisson
with electric field and frictional damping added to the momentum equations. We
show the global existence and $L^{p}$ convergence rates of planar diffusion
waves for multi-dimensional bipolar Euler-Poisson systems when the initial data
are near the planar diffusive waves. A frequency decomposition and approximate
Green function based on delicate energy method are used to get the optimal
decay rates of the planar diffusion waves. To our knowledge, the
$L^p(p\in[2,+\infty])$-convergence rate of planar waves improves the previous
results about the $L^2$-convergence rates.
