  We investigated the out-of-plane transport properties of parent and
chemically substituted BaFe$_{2}$As$_{2}$ for various types of substitution.
Based on the studies of Hall coefficient and chemical-substitution effect, we
have clarified the origin for the unusual temperature dependence of
out-of-plane resistivity $\rho_c(T)$ in the high-temperature
paramagnetic-tetragonal phase. Electron (hole) carriers have an incoherent
(coherent) character, which is responsible for non-metallic (metallic)
$\rho_c(T)$. Although both of electron and hole contributions are almost
comparable, a slightly larger contribution comes from electrons at high
temperatures, while from holes at low temperatures, resulting in a maximum in
$\rho_c(T)$. In the low-temperature antiferromagnetic-orthorhombic phase, the
major effect of substitution is to increase the residual-resistivity component,
as in the case for the in-plane transport. In particular, Co atoms substituted
for Fe give rise to strong scattering with large $\mathit{ac}$ anisotropy. We
found that K substitution induces a non-metallic behavior in $\rho_c(T)$ at low
temperatures, which is likely due to a weakly localized nature along the
$c$-axis direction.
