Ultra-High Boron Doping of Si and Ge for Nanoelectronics and Photonics

• Published in: ECS transactions Vol. 98; no. 5; pp. 203 - 214
• Main Authors: Hartmann, Jean-Michel, Frauenrath, Marvin, Richy, Jérôme, Veillerot, Marc
• Format: Journal Article
• Language: English
• Published: The Electrochemical Society, Inc 08.09.2020
• ISSN: 1938-5862; 1938-6737
• DOI: 10.1149/09805.0203ecst

Si:B or Ge:B layers can used to fabricate devices such as p-type metal oxide semiconductor transistors, photo-detectors, light emitting diodes and so on. We have explored here the in-situ boron-doping of Si and Ge with Si2H6 + B2H6 and Ge2H6 + B2H6. Such chemistries enable Si or Ge epitaxy at temperatures definitely lower than with mainstream precursors such as SiH4 or GeH4. Growth temperatures and pressures in our 200mm Reduced Pressure - Chemical Vapor Deposition tool were 550°C, 20 Torr (Si) and 350°C, 100 Torr (Ge). X-ray Diffraction was used to convert the tensile strain in Si:B or Ge:B layers into substitutional B concentrations, while Secondary Ions Mass Spectrometry gave us the atomic B concentration. As far as Si:B was concerned, a huge growth rate increase (from 9.5 up to 39.8 nm min.-1) was evidenced when adding relatively small amounts of B2H6 to Si2H6. Ultra-high substitutional and atomic boron contents were obtained in those Si:B layers (at most: 2.7x1020 and 1.1x1021 atoms cm-3). For higher B2H6 flows, films became poly-crystalline. A similar growth rate increase (from 5.8 up to 20.8 nm min.-1) and really high substitutional B concentrations (at most: 4.8x1020 atoms cm-3) were otherwise obtained for Ge:B. Such concentrations were several times higher than with conventional chemistries.