Millisecond-Level Minority Carrier Lifetime in Femtosecond Laser-Textured Black Silicon

Femtosecond laser-textured black silicon (fs-bSi) is known to suffer from heavy minority carrier recombination resulted from laser irradiation. In this paper, we demonstrate that the thermal annealing step, generally used to recover the crystal damage, could improve the minority carrier lifetime of the fs-bSi wafers only from 8 μs to 12 μs, even when using as high temperature as 800 °C. However, with an optimized wet chemical etching process, we obtain a high minority carrier lifetime of 2 ms without sacrificing the optical properties of the samples, i.e., the absorptance remains above 90% in the studied wavelength range (250–1100 nm). Increasing the etching time further leads to a total recovery of the lifetime up to 10.5 ms, which proves that the damage originating from the fs-laser texturing extends only to the near-surface layer (a few μm) of silicon.