Study on top sulfur hyperdoping layer covering microstructured Si by fs-laser irradiation

We studied the infrared absorption of a top sulfur hyperdoping layer covering an fs-laser irradiated microstructured Si substrate. To clarify the hyperdoping concentration distributions, and to find out how the top hyperdoping layer affects infrared absorption from 1200 to 2000 nm, a continuous etching treatment was utilized. Then we interpreted the thermal stabilization of both infrared absorption and sulfur hyperdoping concentration. The fundamental cause for infrared-absorption degradation under thermal annealing was explained. Furthermore, we discussed in detail how the interaction between the top hyperdoping layer and surface microstructure contributed to the high infrared absorption by a series of theoretical simulations using a finite-difference time-domain method. A strong localization of an incident electromagnetic wave was observed around the top sulfur hyperdoping layer covering microstructured Si, which played a critical role in improving infrared absorption. The results in this paper are especially beneficial to the subsequent fabrication of photoelectric devices and infrared response improvement.