Mid-infrared absorptance of silicon hyperdoped with chalcogen via fs-laser irradiation

Abstract:

Silicon hyperdoped with heavy chalcogen atoms via femtosecond- laser irradiation exhibits strong broadband, sub-bandgap light absorption. Understanding the origin of this absorption could enable applications for hyperdoped-silicon based optoelectronic devices. In this work, we measure absorption to wavelengths up to 14 μm using Fourier transform infrared spectroscopy and study sulfur-, selenium- and tellurium- hyperdoped Si before and after annealing. We find that absorption in the samples extends to wavelengths as far as 6 μm. After annealing, the absorption spectrum exhibits features that are consistent with free-carrier absorption. Although the surface morphology influences the shape of the absorption curves, the data permit us to place an upper bound on the position of the chalcogen dopant energy levels.