The determination of hydrogen energy levels in semiconducting materials is important owing to the ability of hydrogen impurity to either compensate dopant activity in some materials or to act as a dopant itself in others. Although direct observation of hydrogen levels is difficult owing to its high mobility and reactivity, data can be provided using the hydrogen analog muonium, formed by implantation of positive unions. We present here muonium studies of bulk Si(1-x)Ge(x) alloys aimed at extraction of hydrogen energy levels within this system. A simple band alignment model predicts the behavior of donor and acceptor muonium species across the alloy range. This model is compared with experimentally determined donor and acceptor levels extracted from the temperature dependence of muonium amplitudes. (c) 2007 Elsevier B.V. All rights reserved.