Studies of picosecond carrier dynamics in polysilane alloys : evidence for geminate recombination in small hydrogenated amorphous silicon clusters

The ultrafast photocarrier dynamics in polysilane alloys, amorphous (SiH2)n, has been studied using the picosecond photoinduced absorption (PA) technique. For excitation below the optical gap, the PA response decays exponentially and is faster at low temperatures. This is interpreted in terms of e-h geminate recombination in the small clusters (∼10 Å) of a-Si:H embedded in the polysilane matrix. The PA response with above-gap excitation is similar to that of conventional a-Si:H; it decays much slower in the form of a power law t −β (β