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Hyperdoping silicon with selenium: solid vs. liquid phase epitaxy.

Zhou S, Liu F, Prucnal S, Gao K, Khalid M, Baehtz C, Posselt M, Skorupa W, Helm M - Sci Rep (2015)

Bottom Line: Flash lamp annealed selenium-implanted silicon shows a substitutional fraction of ~ 70% with an implanted concentration up to 2.3%.The resistivity is lower and the carrier mobility is higher than those of nanosecond pulsed laser annealed samples.Our results show that flash-lamp annealing is superior to laser annealing in preventing surface segregation and in allowing scalability.

View Article: PubMed Central - PubMed

Affiliation: Helmholtz-Zentrum Dresden-Rossendorf, Institute of Ion Beam Physics and Materials Research, Bautzner Landstr. 400, 01328 Dresden, Germany.

ABSTRACT
Chalcogen-hyperdoped silicon shows potential applications in silicon-based infrared photodetectors and intermediate band solar cells. Due to the low solid solubility limits of chalcogen elements in silicon, these materials were previously realized by femtosecond or nanosecond laser annealing of implanted silicon or bare silicon in certain background gases. The high energy density deposited on the silicon surface leads to a liquid phase and the fast recrystallization velocity allows trapping of chalcogen into the silicon matrix. However, this method encounters the problem of surface segregation. In this paper, we propose a solid phase processing by flash-lamp annealing in the millisecond range, which is in between the conventional rapid thermal annealing and pulsed laser annealing. Flash lamp annealed selenium-implanted silicon shows a substitutional fraction of ~ 70% with an implanted concentration up to 2.3%. The resistivity is lower and the carrier mobility is higher than those of nanosecond pulsed laser annealed samples. Our results show that flash-lamp annealing is superior to laser annealing in preventing surface segregation and in allowing scalability.

No MeSH data available.


Related in: MedlinePlus

Competition between the Si recrystallization and selenium diffusion characterized by the time needed to regrow (τG) or diffuse (τD) one monolayer.The dashed line is τD in solid phase according to the diffusion parameter in Ref. 45. The other lines or symbols are τG according to different references: open square46, star47, open triangle48, solid square49, open circle20. Despite the possible uncertainty of the regrowth velocity, τG is smaller than τD. That means it is possible to trap selenium and realize metastable, selenium over-saturated Si layer. The vertical dashed and dotted lines indicate the working regime of flash lamp annealing (FLA). The reported τG is shown as a solid triangle2 and τD is shown as a vertical thick line by assuming the growth velocity of 1–10 m/s for pulsed laser annealing (PLA).
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f6: Competition between the Si recrystallization and selenium diffusion characterized by the time needed to regrow (τG) or diffuse (τD) one monolayer.The dashed line is τD in solid phase according to the diffusion parameter in Ref. 45. The other lines or symbols are τG according to different references: open square46, star47, open triangle48, solid square49, open circle20. Despite the possible uncertainty of the regrowth velocity, τG is smaller than τD. That means it is possible to trap selenium and realize metastable, selenium over-saturated Si layer. The vertical dashed and dotted lines indicate the working regime of flash lamp annealing (FLA). The reported τG is shown as a solid triangle2 and τD is shown as a vertical thick line by assuming the growth velocity of 1–10 m/s for pulsed laser annealing (PLA).

Mentions: We try to characterize the competition between the solute trapping and diffusion by estimating the time needed to regrow (τG) or to diffuse (τD) over a Si monolayer (0.27 nm). In other words, the speed of the resolidification and the speed at which the impurity atoms can move determine how likely they will stay ahead or be trapped by the moving amorphous/crystalline interface. If τD is larger than τG, the dopants are able to be trapped in the crystalline matrix. In Figure 6, we compare τG and τD estimated from data published in literature. τD is calculated according to the data in ref. 45. The large uncertainty in τG comes from the large scattering in the regrowth velocity, which exhibits different values reported by various groups2046474849. However, as shown in Fig. 6, in solid phase Si τD is generally larger than τG. That means selenium impurities can be trapped in the Si matrix if an optimized thermal treatment is applied even in solid phase processing. Particularly, in the low temperature regime, τD is much larger than τG, which well explains the realization of doping above solubility limit by low temperature annealing20.


Hyperdoping silicon with selenium: solid vs. liquid phase epitaxy.

Zhou S, Liu F, Prucnal S, Gao K, Khalid M, Baehtz C, Posselt M, Skorupa W, Helm M - Sci Rep (2015)

Competition between the Si recrystallization and selenium diffusion characterized by the time needed to regrow (τG) or diffuse (τD) one monolayer.The dashed line is τD in solid phase according to the diffusion parameter in Ref. 45. The other lines or symbols are τG according to different references: open square46, star47, open triangle48, solid square49, open circle20. Despite the possible uncertainty of the regrowth velocity, τG is smaller than τD. That means it is possible to trap selenium and realize metastable, selenium over-saturated Si layer. The vertical dashed and dotted lines indicate the working regime of flash lamp annealing (FLA). The reported τG is shown as a solid triangle2 and τD is shown as a vertical thick line by assuming the growth velocity of 1–10 m/s for pulsed laser annealing (PLA).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4321182&req=5

f6: Competition between the Si recrystallization and selenium diffusion characterized by the time needed to regrow (τG) or diffuse (τD) one monolayer.The dashed line is τD in solid phase according to the diffusion parameter in Ref. 45. The other lines or symbols are τG according to different references: open square46, star47, open triangle48, solid square49, open circle20. Despite the possible uncertainty of the regrowth velocity, τG is smaller than τD. That means it is possible to trap selenium and realize metastable, selenium over-saturated Si layer. The vertical dashed and dotted lines indicate the working regime of flash lamp annealing (FLA). The reported τG is shown as a solid triangle2 and τD is shown as a vertical thick line by assuming the growth velocity of 1–10 m/s for pulsed laser annealing (PLA).
Mentions: We try to characterize the competition between the solute trapping and diffusion by estimating the time needed to regrow (τG) or to diffuse (τD) over a Si monolayer (0.27 nm). In other words, the speed of the resolidification and the speed at which the impurity atoms can move determine how likely they will stay ahead or be trapped by the moving amorphous/crystalline interface. If τD is larger than τG, the dopants are able to be trapped in the crystalline matrix. In Figure 6, we compare τG and τD estimated from data published in literature. τD is calculated according to the data in ref. 45. The large uncertainty in τG comes from the large scattering in the regrowth velocity, which exhibits different values reported by various groups2046474849. However, as shown in Fig. 6, in solid phase Si τD is generally larger than τG. That means selenium impurities can be trapped in the Si matrix if an optimized thermal treatment is applied even in solid phase processing. Particularly, in the low temperature regime, τD is much larger than τG, which well explains the realization of doping above solubility limit by low temperature annealing20.

Bottom Line: Flash lamp annealed selenium-implanted silicon shows a substitutional fraction of ~ 70% with an implanted concentration up to 2.3%.The resistivity is lower and the carrier mobility is higher than those of nanosecond pulsed laser annealed samples.Our results show that flash-lamp annealing is superior to laser annealing in preventing surface segregation and in allowing scalability.

View Article: PubMed Central - PubMed

Affiliation: Helmholtz-Zentrum Dresden-Rossendorf, Institute of Ion Beam Physics and Materials Research, Bautzner Landstr. 400, 01328 Dresden, Germany.

ABSTRACT
Chalcogen-hyperdoped silicon shows potential applications in silicon-based infrared photodetectors and intermediate band solar cells. Due to the low solid solubility limits of chalcogen elements in silicon, these materials were previously realized by femtosecond or nanosecond laser annealing of implanted silicon or bare silicon in certain background gases. The high energy density deposited on the silicon surface leads to a liquid phase and the fast recrystallization velocity allows trapping of chalcogen into the silicon matrix. However, this method encounters the problem of surface segregation. In this paper, we propose a solid phase processing by flash-lamp annealing in the millisecond range, which is in between the conventional rapid thermal annealing and pulsed laser annealing. Flash lamp annealed selenium-implanted silicon shows a substitutional fraction of ~ 70% with an implanted concentration up to 2.3%. The resistivity is lower and the carrier mobility is higher than those of nanosecond pulsed laser annealed samples. Our results show that flash-lamp annealing is superior to laser annealing in preventing surface segregation and in allowing scalability.

No MeSH data available.


Related in: MedlinePlus