Relation between the substitutional fraction and electrical activation of carbon in heavily C-ion implanted GaAs

Nuclear reaction analysis (NRA), using the ¹²C(d,p) ¹³C reaction, in conjunction with Rutherford backscattering spectrometry (RBS) in the channeling geometry was used to evaluate the substitutional fraction of C in (100)-oriented semi-insulating GaAs implanted with ¹²C ions to a dose of 5 × 10¹⁶ cm^-2. The substitutional fraction of the implanted ¹²C evaluated by NRA was 19% in the samples annealed at 600°C, whereas the electrical activation rate of the same sample was 2.1%, as measured by the van der Pauw method. It is suggested that a possible origin of this discrepancy is the compensating centers such as As vacancy (V_As) and/or V_As-C_As complex introduced in the annealing processes. This was supported by both the surface precipitation of As observed by Raman scattering and the enhancement of the surface peak in RBS-channeling yield which was measured by using a 1.5 MeV ⁴He⁺-ion beam.