Mechanism of photoresponsivity reduction in BaSi2 epitaxial films by post-annealing at moderate temperatures

Photoresponsivity is an important measure for applications as light absorbing layers because it is proportional to carrier lifetime. Previous studies have shown that the photoresponsivity of undoped BaSi2 films increases by more than 10 times by post-annealing (PA) at 1000 degrees C, but decreases by moderate-temperature PA. Such BaSi2 films are compressively strained in the normal direction, regardless of whether they are undoped or As-doped BaSi2 films and show a distinct photoluminescence around 0.85 eV at 8 K, indicating the formation of a new localized state. These provide a clue to the annealing conditions that lead to photoresponsivity reduction.