Muonium analog of hydrogen passivation: observation of the Mu+-Zn- reaction in GaAs.

We report direct detection of the formation and subsequent breakup of a complex containing positively charged muonium ( Mu+) and a substitutional Zn(Ga) acceptor in heavily doped p-type GaAs:Zn. Mu+ diffuses above 200 K with a hop rate nu = nu(0)e(-E(nu)/k(B)T) where nu(0) = (7.7+/-2.0)x10(8) s(-1) and E(nu) = 0.15(4) eV. Above 350 K, it forms the complex with a trapping radius of 500+/-200 A. The Mu-Zn complex breaks up above 550 K with a dissociation energy of 0.88(7) eV and prefactor of (5+/-4)x10(12) s(-1). Above 750 K, the cyclic reaction Mu+<--> Mu0 takes place.

Novel behavior of bond-centered muonium in heavily doped n-type silicon: Curie-like spin susceptibility and charge screening.

Bond-centered muonium ( Mu(0)(BC)) has been observed in very heavily doped n-type Si:P. It exhibits a Curie-like electronic spin susceptibility which leads to a giant negative shift in the muon spin precession frequency. At high dopant levels, the Mu(0)(BC) hyperfine parameters, deduced from a model involving spin exchange with free carriers, are significantly reduced from those in intrinsic Si. This indicates that the spin density distribution for Mu(0)(BC) in metallic Si:P is altered significantly by charge screening effects, likely a general phenomenon for deep impurities in materials with high carrier concentrations.