Diffusion and activation of Si implanted into GaAs

The aim of this work is to optimize the annealing conditions of gallium arsenide implanted with Si ions. Four types of substrates were investigated: undoped GaAs and GaAs doped with either Te; Si or Zn. Implantation was performed at room temperature to a dose of 1.5 x 10(15) cm(-2) at an energy of 150 keV. The samples were annealed at 1000degreesC for I It under the following conditions: in vacuum with a SiO2 film and under As pressure either with or without the oxide layer. The extent of diffusion of the implanted species was characterized using the secondary ion mass spectrometry technique while the electrical activation was evaluated by C-V profiling. The Si diffusion coefficient was found dependent on the initial substrate doping in relation D-(GaAs:Zn) < D-(GaAs) < D-(GaAs:Te). In all cases, the highest electrical activation was obtained by employing as pressure together with the oxide protective cover. In the case of GaAs:Te and GaAs:Si, electron concentration increased more than two times compared to the original sample; in Zn-doped GaAs a well-defined junction was obtained. (C) 2003 Elsevier Science Ltd. All rights reserved.