Spectral and temporal characteristics of light-induced absorption for an undoped and a Rh-doped as-grown crystal were investigated and compared. Two dark-decay time constants corresponding to two shallow levels were observed: 40 ms and 1.2 s for undoped and 39 ms and 3.4 s for Rh-doped The light-induced absorption spectra were resolved into two components according to the dark-decay time constants. The resolved spectra reveal that one shallow level in Rh-doped and one in undoped are caused by a same impurity defect. The thermal activation energies of these levels were determined to be 0.53 and 0.7 eV for undoped and 0.57 and 0.8 eV for Rh-doped The 0.8-eV shallow level in is caused by the other level, 0.57 eV, is the one that has the same defect origin as the 0.53 eV level in undoped Other parameters for the shallow levels are also given.
© 1998 Optical Society of America