Fig. 1

a Absorptance of micro-structured and unstructured silicon samples. b Absorptance spectra for black silicon samples fabricated under different atmosphere of sulfur hexafluoride (solid line), selenium (dashed line), tellurium (dotted line), and nitrogen gas (solid line) [7]. c Absorptance spectra of black silicon samples doped with S, Se, and Te ions after thermal annealing at 775 K for different time (from bottom to top: 24 h, 6 h, 100 min, 30 min, 10 min) [7]. d The absorptance of micro-structured black silicon at 1550 nm with respect to the number of laser pulses used in the irradiation processing [8]. e Photocurrent curves of the micro-structured and traditional silicon-based avalanche photodiodes (APDs) under a light source of 1.310 μm. f I–V curves with different annealing temperature