Manifestation of effective-mass states of secondary minima in the persistent photoconductivity related to the DX centre in
The correlation of persistent photoconductivity and photo-Hall studies of Sn- and Si-doped layers of compositions with previous photo-EPR results obtained on the same samples shows the importance of hydrogenic effective-mass states derived from secondary conduction band minima in highly () doped samples. The Fermi level pinning after low-temperature photoexcitation in direct-gap material by the resonant level in the case of Sn-doped samples, directly demonstrated by its EPR detection, explains the difference in the spin and carrier concentrations observed as well as the different kinetics for the relaxation into the initial state. The consideration of this state allows further an interpretation of the nonmonotonic changes of the free-electron mobility with the photon flux observed in highly doped () samples.