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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

Temperature dependent sheet resistance of selenium implanted Si annealed by FLA (1.3 ms, 3.4 kV) or PLA (308 nm, 28 ns, 0.9 J/cm2):With increasing selenium concentration, an insulator-metal transition occurs for the PLA samples, while all FLA samples show quasi-metallic conduction.
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f4: Temperature dependent sheet resistance of selenium implanted Si annealed by FLA (1.3 ms, 3.4 kV) or PLA (308 nm, 28 ns, 0.9 J/cm2):With increasing selenium concentration, an insulator-metal transition occurs for the PLA samples, while all FLA samples show quasi-metallic conduction.

Mentions: Selenium is a deep donor in Si and its energy level is around 200–300 meV below the Si conduction band38. Upon high concentration doping, an insulator-metal transition was observed in selenium doped Si7. We also measured the electrical properties of selected samples. Figure 4 shows the sheet resistance in the temperature range 4–30 K. Since we use nearly intrinsic Si substrate with a sheet resistance around 1.5×105 ohm/□ at room temperature, the parallel resistance from the substrate is much larger than the selenium doped layer. Therefore, we only measure the conductivity from the doped Si layer. For the PLA samples, an insulator-metal transition occurs with increasing selenium concentration: Sample SiSe1.1 behaves like an insulator with its sheet resistance sharply rising at low temperature. Its conductivity is thermally activated. On the other hand, for the higher doped sample SiSe2.3 the resistance increases only very slightly at low temperature and its conductivity appears to remain finite when the temperature approaches zero. In sharp contrast, flash lamp annealing renders both samples metallic like - the higher doped SiSe2.3, but also the lower doped SiSe1.1. The sheet resistance of sample SiSe1.1FLA is even lower than SiSe2.3PLA with a higher Se concentration, clearly showing the superior (flash-lamp) annealing behavior by solid-phase epitaxy. Finally sample SiSe2.3FLA exhibits the smallest sheet resistance and a clear metal-like conductivity. Its sheet resistance at 5 K is around 190 ohm/□. It corresponds to a conductivity of 500/(ohm·cm) if assuming a thickness of 100 nm. This conductivity is three times larger than sample SiSe2.3PLA. We attribute the large conductivity to the high quality of the recrystallized layer by FLA, which results in a large Hall mobility.


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)

Temperature dependent sheet resistance of selenium implanted Si annealed by FLA (1.3 ms, 3.4 kV) or PLA (308 nm, 28 ns, 0.9 J/cm2):With increasing selenium concentration, an insulator-metal transition occurs for the PLA samples, while all FLA samples show quasi-metallic conduction.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f4: Temperature dependent sheet resistance of selenium implanted Si annealed by FLA (1.3 ms, 3.4 kV) or PLA (308 nm, 28 ns, 0.9 J/cm2):With increasing selenium concentration, an insulator-metal transition occurs for the PLA samples, while all FLA samples show quasi-metallic conduction.
Mentions: Selenium is a deep donor in Si and its energy level is around 200–300 meV below the Si conduction band38. Upon high concentration doping, an insulator-metal transition was observed in selenium doped Si7. We also measured the electrical properties of selected samples. Figure 4 shows the sheet resistance in the temperature range 4–30 K. Since we use nearly intrinsic Si substrate with a sheet resistance around 1.5×105 ohm/□ at room temperature, the parallel resistance from the substrate is much larger than the selenium doped layer. Therefore, we only measure the conductivity from the doped Si layer. For the PLA samples, an insulator-metal transition occurs with increasing selenium concentration: Sample SiSe1.1 behaves like an insulator with its sheet resistance sharply rising at low temperature. Its conductivity is thermally activated. On the other hand, for the higher doped sample SiSe2.3 the resistance increases only very slightly at low temperature and its conductivity appears to remain finite when the temperature approaches zero. In sharp contrast, flash lamp annealing renders both samples metallic like - the higher doped SiSe2.3, but also the lower doped SiSe1.1. The sheet resistance of sample SiSe1.1FLA is even lower than SiSe2.3PLA with a higher Se concentration, clearly showing the superior (flash-lamp) annealing behavior by solid-phase epitaxy. Finally sample SiSe2.3FLA exhibits the smallest sheet resistance and a clear metal-like conductivity. Its sheet resistance at 5 K is around 190 ohm/□. It corresponds to a conductivity of 500/(ohm·cm) if assuming a thickness of 100 nm. This conductivity is three times larger than sample SiSe2.3PLA. We attribute the large conductivity to the high quality of the recrystallized layer by FLA, which results in a large Hall mobility.

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