A reasonable model is proposed to calculatee the temperature dependence of photoconductivity (PC) in a-Si:H and a-Si:H/a-SiNx:H super lattices. Simmons-Taylor theory and the occupation statistics of correlated defects are used to describe band tail states and dangling bonds states. As in a-Si:H/a-SiNx:H superlattices, the electronic potential and charge distributions resulting from space-charge doping are calculated at various amounts of transferred charge and different asymmetry boundary conditions. The DC and PC are calculated with corresponding space potential and charge distributions. It is found that the enhancements of DC and PC in superlattices are mainly determined by the amouns of injected charge, and the influence of interface asymmetry is slight.