Formation and dynamics of muonium centres in semiconductors—a new approach

Abstract

Various processes of muonium atom formation in semiconductorsvia electron capture by a positive muon have been studied usingμSR techniques, including those with applied electric field. Experiments in GaAs,GaP and CdS suggest that the electron is initially captured into a highlyexcited state, from which the cascade down to the muonium ground state goesthrough an intermediate weakly bound state determined by the electron effectivemass and the dielectric constant of the host. The electronic structure of thisweakly bound state is shown to be hydrogenic. The nature of the final (on theμSR timescale) muonium state depends on the energy releasing mechanisms in the cascadeprocess. We suggest that muonium dynamics in semiconductors (including the effects ofelectric and magnetic fields and temperature) reflect the electron dynamics in weaklybound muonium state(s) in which the electron is delocalized over distances of about 100 Å.