  We present a theoretical investigation of shot-noise suppression due to
long-range Coulomb interaction in nondegenerate diffusive conductors.
Calculations make use of an ensemble Monte Carlo simulator self-consistently
coupled with a one-dimensional Poisson solver. We analyze the noise in a
lightly doped active region surrounded by two contacts acting as thermal
reservoirs. By taking the doping of the injecting contacts and the applied
voltage as variable parameters, the influence of elastic and inelastic
scattering in the active region is investigated. The transition from ballistic
to diffusive transport regimes under different contact injecting statistics is
analyzed and discussed. Provided significant space-charge effects take place
inside the active region, long-range Coulomb interaction is found to play an
essential role in suppressing the shot noise at $qU \gg k_BT$. In the elastic
diffusive regime, momentum space dimensionality is found to modify the
suppression factor $\gamma$, which within numerical uncertainty takes values
respectively of about 1/3, 1/2 and 0.7 in the 3D, 2D and 1D cases. In the
inelastic diffusive regime, shot noise is suppressed to the thermal value.
