Quantification of absorption contributions in microstructured silicon fabricated by femtosecond laser pulses

¹ Shanghai Key Lab of Modern Optical System, University of Shanghai for Science and Technology No. 516, Jungong Road, 200093, Shanghai, China
² Department of Engineering Science and Mechanics, The Pennsylvania State University - 201 Old Main, University Park, 16802, PA, USA
³ Department of Physics & Astronomy, Middle Tennessee State University - 1301 East Main Street, Murfreesboro, 37132, TN, USA
⁴ The Institute of Optics, University of Rochester - 500 Joseph C. Wilson Blvd., Rochester, 14627, NY, USA

^(a) ymzhu@usst.edu.cn

Received: 14 April 2015
Accepted: 22 June 2015

Abstract

Microstructured silicon material, fabricated by femtosecond laser pulses, has a lot of crucial applications in silicon-based photovoltaics, photo-detectors, and super-hydrophobic devices etc., due mainly to the high absorption in both visible and infrared regions. However, the mechanisms attributed to its high-absorption characteristics have never been accurately quantified, which limits further the exploitation of this kind of material. Here, we experimentally quantify different absorption contributions in microstructured silicon fabricated by femtosecond laser pulses, which can be attributed to dopant impurities in the silicon substrate, doping impurities induced during the laser fabrication process, absorption enhancement from the light-trapping structure, and surface disordered material formed also during the laser fabrication process. From these analyses, we determine that with the assist of a light-trapping structure, dopant impurities in the silicon substrate contribute much more to the infrared absorption than those of the doping sulfur impurities induced during the fabrication process. Furthermore, the infrared absorption of material can be annealing-insensitive. These results have important implications for the design and fabrication of high-efficiency optoelectronic devices.