Improvement of excess-carrier lifetime in BaSi2 epitaxial films by post-growth annealing

We have found that post-growth annealing of BaSi₂ epitaxial films drastically modifies carrier-recombination kinetics. In fact, the 1/e decay time of excess carriers in 1640-nm-thick BaSi₂ film annealed at 800 °C is 0.86 μs, which is much longer than that in the as-grown film (0.015 μs). Possible reason for the lifetime increase is discussed from the viewpoint of strain relaxation. The increased lifetime permits us to extract the minority-carrier lifetime from the injection-level dependence of apparent lifetime, which is up to 11 μs in the annealed films. This long lifetime confirms that earth-abundant BaSi₂ is promising for thin-film solar cells.