Enhanced vertical photo-sensitivity in μc-Si:H/a-Si:H superlattices

The microcrystalline silicon/amorphous silicon (μc-Si:H/a-Si:H) superlattice showed an enhanced vertical photo-sensitivity (photo-conductivity/dark-conductivity), whereas it reserved a lateral photo-sensitivity nearly unchanged. The film was fabricated by alternating the mixing of SiH4 and H2 in a photo-chemical vapor deposition system. The fact that a high vertical photo-sensitivity and an obvious crystalline volume fraction can be obtained at the same time distinguishes the μc-Si:H/a-Si:H superlattice from the bulk μc-Si:H. The change of the vertical dark-conductivity with the sublayer thickness was explained by the change of the a-Si:H sublayer’s electrical conduction property. We think that the thin a-Si:H sublayers play an important role of perturbing a columnar structure of the μc-Si:H.