Poster Presentation 24th Australian Conference on Microscopy and Microanalysis 2016

Filamentary cellular breakdown in hyperdoped silicon by ion implantation and pulsed laser melting (#299)

Wenjie Yang 1 , Lachlan A Smillie 1 , Austin J Akey 2 , Michael J Aziz 3 , Jim S Williams 1
  1. The Australian National University, Acton, ACT, Australia
  2. Massachusetts Institute of Technology, Cambridge, MA, USA
  3. Harvard John A. Paulson School of Engineering and Applied Sciences, Cambridge, MA, USA

It has been previously demonstrated that gold hyperdoped silicon by ion implantation and pulsed laser melting exhibits strong sub-band gap absorption, allowing for the fabrication of an infrared photodetector1 . It was hypothesized that this absorption could be further improved by at least an order of magnitude by increasing the substitutional gold concentration. However, it is widely known that transition metals in silicon at sufficiently high concentrations induce the formation of nanostructures called “cellular breakdown” following the resolidification of silicon. In this process, precipitates and silicides are observed to form solute rich filaments that extend to the surface, creating “cell-walls”2 3 . Since non-soluble dopants are not optically active, “cellular breakdown” has traditionally been avoided in previous work.

In this study, the atom location of the supersaturated Au in the Si lattice that has undergone cellular breakdown is analysed using high resolution Rutherford backscattering spectrometry combined with ion channeling (RBS/C). In addition, cross-sectional transmission electron microscopy (XTEM) and energy dispersive spectroscopy (EDS) has been employed to examine the morphological features and composition. Furthermore, the cellular breakdown morphology in the hyperdoped Si:Au system is compared with the hyperdoped Si:Co system as studied by atom probe tomography (APT) at nanometre scale resolution4 .

  1. Mailoa, J.P., et al., Room-temperature sub-band gap optoelectronic response of hyperdoped silicon. Nat Commun, 2014. 5: p. 3011.
  2. Recht, D., et al., Supersaturating silicon with transition metals by ion implantation and pulsed laser melting. Journal of Applied Physics, 2013. 114(12): p. 124903.
  3. Warrender, J.M., et al., Morphological stability during solidification of silicon incorporating metallic impurities. Journal of Applied Physics, 2014. 115(16): p. 163516.
  4. Akey, A.J., et al., Single-Phase Filamentary Cellular Breakdown Via Laser-Induced Solute Segregation. Advanced Functional Materials, 2015. 25(29): p. 4642-4649.