Competition between long-living and D-(A+) states of donors and acceptors in silicon

The photoconductivity (PC) spectra and the induced absorption of background radiation in the energy range 10 to 40 meV are investigated in relatively low compensated B-, Ga- and As-doped Si at 4.2 K. Dips, corresponding to the photoionization of long-living excited states of B and As, are observed in the PC spectra of the D-(A(+)) bands. It was found, that PC of the bands has a slow relaxation (approximate to 10(-4) s). So, the localization of nonequilibrium carriers in long-living excited states of B and As and in the D-(A(+)) states leads to a competition of both slow relaxation processes in PC and absorption phenomena. The separation of the processes is possible in electric field. It leads to a decrease of PC due to D-(A(+)) states but weakly influences the long-living excited states absorption.