Evidence for a shallow muonium acceptor state in Ge-rich Cz-Si1-xGex

Abstract

We have observed muon spin rotation (mu SR) features that are consistent with a shallow muonium (Mu) acceptor state for several Ge-rich silicon germanium alloy compositions. The Mu(T)[0/-] defect level crosses into the valence band at a Ge content of roughly 92%, indicating that a shallow acceptor state should be formed for muons that stop in the acceptor related T-site. For Si0.09Ge0.91, the difference between the diamagnetic amplitudes from RF-driven resonance measurements compared to TF-mu SR indicates a slowly formed state at temperatures below 50 K, consistent with a valence-band resonant Mu(-) that would form the core of a shallow Mu acceptor. We report a summary of hyperfine characterization and transition energies of the various T-site muonium states in Ge-rich alloys and discuss options for the conditions under which shallow acceptor states may be observed by mu SR. (C) 2009 Elsevier B.V. All rights reserved.