Au-rich filamentary behavior and associated subband gap optical absorption in hyperdoped Si

• Main Authors: Yang, W. (Author), Akey, A. J. (Author), Smillie, L. A. (Author), Johnson, B. C. (Author), McCallum, J. C. (Author), Macdonald, D. (Author), Aziz, M. J. (Author), Williams, J. S. (Author), Mailoa, Jonathan P (Contributor), Buonassisi, T. (Contributor)
• Other Authors: Massachusetts Institute of Technology. Department of Physics (Contributor)
• Format: Article
• Language: English
• Published: American Physical Society, 2018-05-21T14:50:32Z.
• Subjects: Article
• Online Access: Get fulltext

 Au-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 (>1×10[superscript 20] cm[superscript −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.