Enhanced light-absorption and photo-sensitivity in amorphous silicon germanium/amorphous silicon multilayer

We investigated the characteristics of the amorphous silicon germanium/amorphous silicon (a-SiGe:H/a-Si:H) multilayers processed through alternate germanium incorporation by adding GeH4 at a fixed periodicity to a constant gas glow of SiH4 in a PECVD deposition process. We found an enhanced optical absorption in the multilayers compared to bulk amorphous silicon germanium (a-SiGe:H) samples with similar averaged incorporated Ge contents. We also found that, in a certain condition, the multilayer shows an obvious enhancement of the photosensitivity (photoconductivity to dark conductivity ratio) to reach a value of 8.5×103. We attribute these beneficial effects to the decreased Ge-related defects in the multilayer.