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 th
e photoionization of long-living excited states of B and As, are observed i
n 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 no
nequilibrium 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 i
n electric field. It leads to a decrease of PC due to D-(A(+)) states but w
eakly influences the long-living excited states absorption.