Muon-spin-resonance study of muonium dynamics in Si and its relevance to hydrogen

The dynamics of transitions among muonium (Mu) states in Si have been studied by radio-frequency (rf) muon-spin-resonance techniques. A total of ten samples doped to roughly 10¹⁵ cm^-3 p type and to 10¹⁶ cm^-3 n type were investigated at temperatures from 10 to 500 K. The normalized rf asymmetry for the ionized center in the p-type samples is well described by a three-state strong-collision model involving MuBC⁺, MuBC⁰, and MuT⁰. Addition of MuT^- and related transitions complicates the model for intermediate n-type concentrations; however, at higher n-type levels a modified three-state model with MuT^- replacing MuBC⁺ successfully describes the charged-state intensities. Observed features are assigned to seven separate transition processes and a single set of parameters, obtained primarily from fits to two samples, provide an excellent description over the full doping range. The Mu results correlate well with the few analogous hydrogen measurements and imply rapid transitions among several hydrogen states under typical experimental conditions.