Hyperdoping Si with chalcogen: solid vs. liquid phase epitaxy

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 Si, the materials were previously only realized by femtosecond or nanosecond laser annealing of implanted Si or bare Si in certain background gases. The high energy density deposited on the Si surface renders it into a liquid phase and the fast recrystallization velocity allows trapping of S/Se/Te into the Si matrix. However, this method encounters a problem of S/Se/Te surface segregation. In this Letter, 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 Se-implanted Si shows a substitutional rate of more than 70% with the implanted concentration up to 1-2%. The resistivity is lower and the carrier mobility is higher than those of laser annealed samples. Our results show that flash lamp annealing is superior laser annealing in preventing surface segregation and in allowing scalability.