Annealing-insensitive “black silicon” with high infrared absorption

A black silicon structure with high-aspect-ratio surface spikes was designed and fabricated in vacuum, resulting in absorptance >90% over the range of 200–2500 nm. It is demonstrated that annealing, an essential step in the fabrication of semiconductor devices, has almost no effect on the infrared absorption of this material, while the infrared absorption of an identical structure fabricated in a SF6 drops dramatically after the annealing process. The characteristic of high infrared absorption and annealing-insensitivity is attributed to both the high-aspect-ratio structure and the phosphor-doped low impedance silicon. These results are important for the fabrication of highly efficient optoelectronic devices.