Silicon microholes array fabricated by femtosecond laser pulses directly writing assisted with further electrochemical etching

Silicon microholes array have been fabricated using femtosecond laser directly writing followed by electrochemical etching in a hydrofluoric acid (HF) and the isopropyl alcohol ((CH₃)₂CHOH) solution. Firstly, the micro size scratches array were directly written on a surface of the n-type, 1-5 Ωcm, Si(100) wafer by using the femtosecond laser pulses. Shallow micro holes array could be obtained on the wafer surface. Then, the as-fabricated sample with shallow micro holes array was further etched electrochemically in HF and (CH₃)₂CHOH solution. During this step, the depth of the shallow microholes array could be greatly enlarged because of the focusing effect by the prefabricated microholes array. Finally, optical characteristics of the fabricated silicon microholes (SiMHs) array at different stages demonstrate that the reflections of the fabricated samples have been greatly reduced compared to that of a silicon wafer. Our method suggests the effectiveness of SiMHs array on a silicon wafer for obtaining the enhanced optical absorption and potential application for fabricating a special radial p-n junction solar cell.