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

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.