A study of EL2 photoquenching properties by photoconductivity measurements of SI GaAs: Cr
The time dependence of the EL2 photo-response shows that in the case of semi-insulating chromium-doped GaAs, the well known photoquenching effect is, in fact, preceded by a 'photo-enhancement'. It is shown that this effect cannot be explained using the classical assumption of a single ionised state for EL2. A tentative explanation involving at least two ionised states is proposed.