Abstract: In this paper, the product of space charge density and scattering cross section has been calculated from the measured room temperature mobility by the use of Matthiessen's rule. A linear relationship between N_SCA and N_D has been found. On the basis of this relationship, the space charge center presented in undoped VPE GaAs epilayers is postulated to be a complex of the SiGa (O₁, V₁) type.
Besides, an in site sulpher remover has been designed and used in the AsCl₃-Ga-H₂ epitaxial system for the first time, and found to be quite effective in depressing the carrier concentration of the epilayers.