Abstract: A proportionality relationship has recently been found to exist between the density of the EL2 electron trap in VPE GaAs and the As/Ga ratio in the gas phase, and also between the ratio[C]/[EL2] and n_300K for VPE GaAs grown in N², where C is a new electron trap found by Ozeki et al. These relationships have led us to the supposition that C and EL2 might be (VGa) 2 and AsGaVGaVAs respectively, and the equilibrium among AsAs (VGa) 2 and AgGaVGaVAs has been named as the C-EL2 or C-A equilibrium.