We applied the layer by layer deposition technique to make low band gap a-Si:H by varying preparation parameters of substrate temperature and hydrogen plasma exposure (HPE) time. With the increase of HPE time up to 24s, the dark conductivity decreases, and then increases rapidly, and the change in photoconductivity is relatively small. Above 50s of HPE time, the microcrystalline Si is formed, confirmed from the Raman scattering and conductivity. We obtained a-Si:H film by HPE technique with optical gap of 1.67eV, photosensitivity of > 10(6), conductivity activation energy of 0.95eV, and hydrogen content of < 9 at.%. The Staebler-Wronski effect of this film is greatly reduced compared with single-layered a-Si:H film deposited at the same temperature.