Coimplantation of carbon and group II acceptors in GaAs

Coimplantation of carbon and one of the group II acceptors Mg, Zn, or Cd, was performed in GaAs using doses of 5×1014 cm−2, and the resulting p-type electrical activity was studied. Carbon and group II coimplantation offers a means of maintaining the III–V stoichiometry, which is known to be beneficial for both carbon and group II activation. The group II implantation profiles show reduced diffusivity from the balance in stoichiometry the carbon coimplantation provides. The group II elements Zn and Cd create substantial implantation damage and therefore help assist carbon activation by supplying the necessary abundance of As vacancies. The Mg coimplantation, because of the light mass of the ion, does not create a significant amount of lattice damage at this dose and consequently the implanted carbon remains inactive, which results in reduced conductivity. This investigation differs from past group III and carbon coimplantation studies because both of the coimplanted species, the group II and carbon, contribute to p-type conductivity as well as help to maintain the stoichiometry.