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

Abstract

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.

An In-Depth Study of the Boron and Phosphorous Doping of GeSn

“…m was equal to 0.05 for GeSn:B, a value nearly 14 times lower than the m = 0.68 value obtained for Ge:B grown at 350 °C, 100 Torr with Ge 2 H 6 + B 2 H 6 . 27 For GeSn:P, m was equal to 0.14, a value 3.4 times smaller than the m = 0.47 value obtained for Ge:P grown at 350 °C, 100 Torr with Ge 2 H 6 . 28 Dopant incorporation was thus more difficult in GeSn than in pure Ge, especially for boron.…”

“…a value nearly ten times lower than the 4.8 × 10 20 cm −3 maxima in the literature for Ge:B grown at 350 °C, 100 Torr with Ge 2 H 6 + B 2 H 6 . 27 Such boron concentrations should nevertheless be high enough for use in GeSn photodiodes and light emitting devices.…”

“…Similar increases were found for Ge:B and Ge:P grown at 350 °C, however. 27,28 The constant Sn GR component and the increase of the Ge GR component at high MFRs are likely due to an increased incorporation of Ge thanks to B and P opening surface sites. The Ge GR component is most likely surface reaction rate limited, while the Sn GR component is most likely mass-transport limited, as suggested in the literature.…”

Advances in In Situ Boron and Phosphorous Doping of SiGeSn

“…m was equal to 0.05 for GeSn:B, 23 0.42 for SiGeSn:B (current results) and 0.68 for Ge:B. 29 Meanwhile, m was equal to 0.14 for GeSn:P, 23 0.25 for SiGeSn:P (current results) and 0.47 for Ge:P. 45 As all layers were grown at 350 °C, 100 Torr with a Ge 2 H 6 + Si 2 H 6 + SnCl 4 + PH 3 or B 2 H 6 chemistry, it thus meant that dopant incorporation was more efficient in SiGeSn than in GeSn and close to that in Ge.…”

“…The ion concentration was, however, limited to 5.2 × 10 19 cm −3 , a value almost ten times lower than in in situ doped Ge:B (4.8 × 10 20 cm −3 ). 29 For GeSn:P, it was found that, for high dopant flows, P atoms were not fully electrically activated, most likely because of the formation of electrically z E-mail: marvin.frauenrath@st.com ECS Journal of Solid State Science and Technology, 2023 12 064001 inactive Sn m P n V clusters. In this study, it is aimed to overcome these shortcomings by switching over to in situ doped SiGeSn and investigate the growth mechanics, composition and electrical activation of dopants.…”