Microscopy and Microanalysis

Materials Applications

Selenium Segregation in Femtosecond-Laser Hyperdoped Silicon Revealed by Electron Tomography

Georg Haberfehlnera1 c1, Matthew J. Smitha2, Juan-Carlos Idroboa3, Geoffroy Auverta4, Meng-Ju Shera5, Mark T. Winklera5, Eric Mazura5, Narciso Gambacortia1, Silvija Gradečaka2 and Pierre Bleueta1

a1 CEA, LETI, MINATEC Campus, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France

a2 Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA

a3 Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA

a4 STMicroelectronics, 850 Rue Jean Monnet, 38926 Crolles, France

a5 Department of Physics and School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA

Abstract

Doping of silicon with chalcogens (S, Se, Te) by femtosecond laser irradiation to concentrations well above the solubility limit leads to near-unity optical absorptance in the visible and infrared (IR) range and is a promising route toward silicon-based IR optoelectronics. However, open questions remain about the nature of the IR absorptance and in particular about the impact of the dopant distribution and possible role of dopant diffusion. Here we use electron tomography using a high-angle annular dark-field (HAADF) detector in a scanning transmission electron microscope (STEM) to extract information about the three-dimensional distribution of selenium dopants in silicon and correlate these findings with the optical properties of selenium-doped silicon. We quantify the tomography results to extract information about the size distribution and density of selenium precipitates. Our results show correlation between nanoscale distribution of dopants and the observed sub-band gap optical absorptance and demonstrate the feasibility of HAADF-STEM tomography for the investigation of dopant distribution in highly-doped semiconductors.

(Received October 19 2012)

(Accepted January 30 2013)

Key words

  • electron tomography;
  • HAADF-STEM;
  • femtosecond pulsed laser irradiation;
  • optical hyperdoping;
  • dopant segregation

Correspondence

c1 Corresponding author. E-mail: georg.haberfehlner@cea.fr