Ion Implantation in Gallium Arsenide

Ion implantation is a useful method to incorporate dopants into semiconductors. Understanding implantation processes is essential to the advancement of solid state technology. Because of its technical importance, gallium arsenide (GaAs) was chosen for this study. Hall effect, x-ray diffraction, and electrochemical capacitance-voltage (CV) profiling were used to study activation of silicon implants as functions of dose and annealing temperature and time. The annealing of crystalline damage and activation of dopants proceeds in a definite sequence. Implantation damage is annealed at approximately 625^ circC, with activation taking place between 625 and 675^circC. The electron profiles arising from Si implantation into GaAs possess long tails. Increasing the annealing temperature to greater than 900^circC results in a shortening of the tail because of the formation of an unknown acceptor defect. This result is reproducible and was used to enhance the performance of GaAs JFETs. Co-implantation of In or Ga with C was investigated by Local Vibrational Mode Spectroscopy (LVM), Rutherford Backscattering (RBS), Particle-Induced X-Ray Emission (PIXE), Photoluminescence (PL), and Hall effect. The dose of the C was 5 times 10^ {14} cm^{-2} 27 keV, while the doses of In, 185 keV, or Ga, 160 keV, ranged from 5 times 10 ^{13} to 5 times 10^{15} cm ^{-2}. The data shows that 99% of the C, when implanted alone and annealed, is not located as isolated, substitutional atoms on either sublattice, but in non-substitutional, inactive sites. The co-implanted ion acts to increase both the concentration of C _{rm As} ((C_ {rm As})) and the sheet hole concentration. For co-implant doses of 5 times 10 ^{13} and 5 times 10^{14} cm ^{-2}, these values are in good agreement. A co-implant dose of 5 times 10^{15} cm ^{-2} results in a hole concentration that is 30% less than the (C_{rm As}) and the co-implanted ions begin to occupy non-substitutional sites. The reduction in the concentration of holes due to C_{rm As} appears to be caused by a compensating donor defect which limits the maximum sheet hole concentration obtainable by the co-implantation technique in GaAs.