Muonium in InSb: Shallow acceptor versus deep trap or recombination center

Abstract

The bound state of a muonium atom has been detected in both $n$-type and $p$-type InSb using a high-field $\ensuremath{\mu}\mathrm{SR}$ technique. The hyperfine constant obtained for this isotropic center $({A}_{\mathrm{T}}=2464\ifmmode\pm\else\textpm\fi{}1\phantom{\rule{0.3em}{0ex}}\mathrm{MHz})$, roughly half that of a Mu atom in vacuum, is characteristic of deep level ${\mathrm{Mu}}^{0}$ centers at tetrahedral interstitial sites in other cubic semiconductors, which typically ionize above $250\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. In contrast, the ${\mathrm{Mu}}^{0}$ signal in InSb begins to disappear near $20\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, which is more characteristic of ionization of a shallow level impurity. The charge-state dynamics of Mu in InSb can be understood in terms of the predicted shallow acceptor behavior for H in InSb versus a deep hole trap or recombination center, rather than as ionization via electron promotion to the conduction band.