Positron annihilation spectroscopic measurements were carried out in order to study the defect properties of semi-insulating GaAs after copper diffusion. A 30nm-layer of Cu was deposited by evaporation to undoped GaAs samples. The diffusion of Cu was performed during an annealing step at 1100C under different arsenic vapour pressures. The samples were quenched into room temperature water. The initial semi-insulating undoped GaAs sample showed no positron traps in that state. After gentle annealing, a vacancy-type defect complex in addition to shallow positron traps was observed to be an efficient positron trap. After Cu in-diffusion during the annealing process, the shallow positron trap was believed to be the CuGa double acceptor. The exact nature of the vacancy-like defects could not be determined unambiguously. The concentration of these defects exhibited inverse relationship to the arsenic vapour pressure. Thus, the arsenic vacancy was believed to be part of this complex. The temperature-dependent Hall-effect measurements revealed the presence of an acceptor level at EV + 0.5eV that was usually attributed to CuGa.

Detection of Vacancy-Like Defects during Cu Diffusion in GaAs by Positron Annihilation. M.Elsayed, V.Bondarenko, K.Petters, R.Krause-Rehberg: Journal of Physics - Conference Series, 2011, 265[1], 012005