The co-implantation of C and a group-II acceptor (Mg, Zn, Cd) was performed, and the results were compared to those of implantation which involved only a single element (Mg, Zn, Cd) or Ga plus C which were co-implanted. The group-II and C/II co-implantation acted so as to balance the crystal stoichiometry, since group-II atoms preferred to reside in the Ga sub-lattice and C preferred to reside in the As sub-lattice. The electrical characteristics of the various implantations were deduced from sheet and differential Hall measurements. Rutherford back-scattering spectrometry was used to determine the amount of implantation-induced damage, and this was then correlated with the amount of C activation in the II/C co-implanted samples. It was found that co-implantation of the heavier group-II acceptors (Zn, Cd) resulted in layers with higher peak hole concentrations. This was a result of the large amount of lattice damage which was created by these elements and which was thought to provide the necessary abundance of As vacancies for C activation. Secondary-ion mass spectroscopic measurements of the samples, after implant-activation, indicated that C co-implantation significantly reduced the diffusivity of the group-II acceptors. Cross-sectional transmission electron microscopy indicated the presence of a unique defect structure (extrinsic dislocation loops) in the case of II/C co-implantation. These dislocation loops were located at the diffusion front of the group-II element in the samples, and therefore had a profound effect upon the diffusion of the group-II elements.

Carbon and group-II acceptor co-implantation in GaAs R.Morton, S.S.Lau, D.B.Poker, P.K.Chu, K.K.Fung, N.Wang: Journal of Applied Physics, 1998, 84[9], 4929-34