Au-rich filamentary behavior and associated subband gap optical absorption in hyperdoped Si
Smillie, L. A.
Mailoa, J. P.
Johnson, B. C.
McCallum, J. C.
Williams, J. S.
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CitationYang, W., A. J. Akey, L. A. Smillie, J. P. Mailoa, B. C. Johnson, J. C. McCallum, D. Macdonald, T. Buonassisi, M. J. Aziz, and J. S. Williams. 2017. “Au-Rich Filamentary Behavior and Associated Subband Gap Optical Absorption in Hyperdoped Si.” Physical Review Materials 1 (7) (December 22). doi:10.1103/physrevmaterials.1.074602.
AbstractAu-hyperdoped Si, synthesized by ion implantation and pulsed laser melting, is known to exhibit a strong sub-band gap photoresponse that scales monotonically with the Au concentration. However, there is thought to be a limit to this behavior since ultrahigh Au concentrations (>1 × 1020 cm−3) are expected to induce cellular breakdown during the rapid resolidification of Si, a process that is associated with significant lateral impurity precipitation. This work shows that the cellular morphology observed in Au-hyperdoped Si differs from that in conventional, steady-state cellular breakdown. In particular, Rutherford backscattering spectrometry combined with channeling and transmission electron microscopy revealed an inhomogeneous Au distribution and a subsurface network of Au-rich filaments, within which the Au impurities largely reside on substitutional positions in the crystalline Si lattice, at concentrations as high as ∼3 at. %. The measured substitutional Au dose, regardless of the presence of Au-rich filaments, correlates strongly with the sub-band gap optical absorptance. Upon subsequent thermal treatment, the supersaturated Au forms precipitates, while the Au substitutionality and the sub-band gap optical absorption both decrease. These results offer insight into a metastable filamentary regime in Au-hyperdoped Si that has important implications for Si-based infrared optoelectronics.
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