Improved activation of Mg+ and As+ dual implants in GaAs by capless rapid thermal annealing

Abstract

The activation of high dose Mg⁺ implants (1×10¹⁵ cm⁻², 100 keV) in GaAs using capless rapid thermal annealing has been improved by the co‐implantation of As⁺. This technique reduces the outdiffusion of the implanted Mg, which can adversely affect the activation of shallow, high dose implants. Compared with an activation of 18% for an implant of Mg⁺ only, the co‐implantation of As⁺ has increased the activation to as much as 61% with concomitant sheet resistance of 136 Ω/⧠. The placement of the As⁺ implant with respect to the position of the Mg⁺ profile has been determined to play a role in the activation efficiency. This technique has been applied to the formation of thick p⁺ regions with high surface carrier concentrations, which has important applications in device fabrication for reduction of contact resistances.