Electrical and optical characterization of Cd+ and P+ dually ion-implanted GaAs

Electrical and optical properties in Cd+ singly and Cd+P+ dually implanted GaAs have been investigated. Samples were annealed by a furnace and characterized by the Van der Pauw method at room temperature and photoluminescence (PL) measurement at 2 K. It is found that a higher activation efficiency of the Cd impurities could be obtained by coimplantation of phosphorous ions. The optimum condition is that Cd+ ions and P+ ions are implanted with the same concentration for high dose implantation. In PL spectra, the intensity of the conduction band to Cd acceptor transition, (e,Cd), in the Cd+ implanted sample increases with increasing phosphorous concentration, which is consistent with the electrical results. PL spectra at the long wavelength region measured by a germanium detector show that P+ ion coimplantation does not produce any deep levels in GaAs. All the results indicate that phosphorous is an ideal species for coimplantation.