Laser hyperdoping silicon for enhanced infrared optoelectronic properties

Pulsed laser melting and rapid solidification have attracted interest for decades as a method to achieve impurity concentrations in silicon orders of magnitude above the equilibrium solubility limit. The incorporation of sulfur into silicon using this technique led to the observation of strong broadband infrared absorption in the resulting material. This observation, combined with interest in impurity band optoelectronic device concepts, has resulted in renewed interest in laser techniques for achieving high impurity concentrations. In this paper, I review the literature that led to the present understanding of laser hyperdoping and provide a summary of the optical and optoelectronic measurements made on sulfur hyperdoped silicon to date. I mention recent work exploring transition metal impurities and discuss how considerations discovered in early solidification and later rapid solidification work inform our approaches to kinetically trapping such impurities. I also provide a simplified picture of how a laser hyperdoping process is typically carried out, as an entry point for an experimentalist seeking to fabricate such layers.