Selective dominance of photoluminescence lifetime in a-Si:H-based alloys

At 13 K, a distribution of photoluminescence (PL) lifetimes, G(τ), for a-Si:H and wide-gap alloys containing C, N or O was dominated by the lifetime component peaked at around 1 ms, whereas, in a-SiGe:H with Ge>20 at.%, G(τ) was dominated by a lifetime component peaked at about 10 μs, which became evident in other alloys at elevated temperatures. The G(τ) for alloys with reduced Ge<10 at.% has been found to contain the 1-ms component even at 13 K, although the 10 μs component was still dominant. I suggest that those two specific photoluminescence lifetime components, which are observed commonly in G(τ) for the a-Si:H-based alloys, come from a localized luminescent center associated with some structural unit which can have two configurations.