Fine structure of the oxygen-related local mode at 714 cm−1 in GaAs

Infrared absorption measurements on a new third state of the Ga-O-Ga center in GaAs are reported. This state gives rise to a local mode at 714 cm−1, B′, which is shifted from the band B to lower energy by 0.67 cm−1. The B′ state acts as an intermediate state for the photoinduced conversion from the 730 cm−1 band, A, to B. The kinetics is quantitatively described by a model considering successive capture of conduction-band electrons, which have been photoexcited from the EL2 level. The reappearance of the band A after quenching of EL2 occurs through the corresponding sequence B→B′→A. The experimental results favor the interpretation of B′ in terms of a third charge state being not accessible at thermal equilibrium conditions.