New approach for the spectroscopy of an isolated hydrogen-like atom in semiconductors by mu SR under laser irradiation

Recently, mu SR under pulsed laser excitation has been developed at KEK-MSL . By applying this powerful new technique to the muonium (as an isolated hy drogen analog) in non-doped GaAs, significant changes in time-dependent lon gitudinal muon spin relaxation were observed. Muonium located around Ga-As bond center is established to be a recombination center. On the other hand, muonium at tetrahedral site in GaAs behaves as a spectator to photoexcited carrier at low temperature (similar to 90 K). Direct evidence was also obt ained for the secondary propagation of the local excitation into the bulk b y the photon recycling mechanism for the first time. (C) 2001 Elsevier Scie nce B.V. All rights reserved.