In this paper we present experimental evidence supporting that persistent behavior in the electronic and optical properties of bulk GaAs and AlGaAs can have different origins as: the metastability of a defect, the persistent charge transfer from a defect to another defect, and the transfer from a defect to the conduction band. In particular, we show three different cases in which defects are either directly or indirectly related to persistent changes of the optical absorption, the magnetic circular dichroism of the absorption (MCDA) and the photoconductivity (PC). The three cases are as follows: the transfer of EL2 to the metastable state EL2(0*) in semi-insulating (SI) GaAs causing persistent quenching of the absorption and photoconductivity (PPCQ); the persistent transfer of electrons from stable EL2(0) to arsenic vacancies in lightly n-type GaAs; and the correlated appearance of persistent MCDA and photoconductivity in AlGaAs due to the photoionization of DX-centers.
