A new method of cleaning a Ge wafer based on a wet chemical treatment and Si1-x-yGexCy/Ge(001) metalorganic molecular beam epitaxial (MOMBE) growth has been performed. It consists of removing the native oxide by ammonia aqueous followed by a diluted sulfuric acid rinse and hydroperoxide treatment to form a passive oxide layer. An extremely uniform surface was obtained by 300 s ammonia etching of the native oxide. Thickness of the oxide layer grown in hydroperoxide is estimated to be approximate to 1.87 nm using angle-resolved X-ray photoelectron spectroscopy measurement. A well-ordered 2 x 1 reflection high-energy electron diffraction pattern appeared after 400 degrees C, 30 min annealing in ultra high vacuum. Si1-x-yGexCy MOMBE growth has been performed on cleaned Ge(001) using disilane (Si2H6) and monomethylgermane (CH6Ge). The (001) axis of the ternary alloy layers is oriented toward Ge(001). No peak corresponding to SiC was detected in X-ray diffraction data.