RTA and FLA of ultra-shallow implanted layers in Ge

The formation of ultra-shallow n⁺ layers by P or As implantation and subsequent rapid thermal annealing (RTA) or flash-lamp annealing (FLA) is investigated. The focus is on diffusion and activation of dopants. RTA leads to considerable broadening of the shallow as-implanted profiles by concentration-dependent diffusion. In contrast, FLA does not cause any diffusion and is therefore a promising method for producing ultra-shallow n⁺p junctions in Ge. Under present annealing conditions RTA yields maximum activation levels of about 1.1E19 and 6.5E18 cm⁻³ for P and As, respectively. The maximum activation achieved by FLA is about 4.0E19 and 2.1E19 cm⁻³ for P and As, respectively. Possible mechanisms for diffusion and deactivation of dopants are discussed.