Positron lifetime and Doppler broadening spectroscopy were applied to the study of the defect properties of semi-insulating GaAs after the diffusion of Cu. A 30nm layer of Cu was deposited by evaporation onto the undoped GaAs samples. The diffusion of Cu was performed during an annealing step at 1100C under various As vapor pressures. The samples were quenched into room-temperature water. The initial semi-insulating undoped GaAs sample exhibited no positron traps. After annealing, a vacancy-type complex and a shallow positron trap were observed to be efficient positron traps. Due to the Cu contamination during the annealing process, the shallow trap was believed to be the CuGa double acceptor. The nature of the vacancy-type defects could not be determined unambiguously. The concentration of these vacancies exhibited inverse relationship with regard to the As vapor pressure that implicated the As vacancy as being part of this complex. Moreover, Doppler-coincidence spectroscopy showed clearly that Cu atoms were not bound in the direct vicinity of the observed vacancies.

Vacancy Generation during Cu Diffusion in GaAs. M.Elsayed, V.Bondarenko, K.Petters, J.Gebauer, R.Krause-Rehberg: Journal of Applied Physics, 2008, 104[10], 103526