A deposition reaction mechanism for Si1-xGex epitaxial growth from silane/germane mixtures is proposed. The resulting growth rate expression, the parameters of which are determined with a least square method, is consistent with available data and it predicts all three distinctive vends observed : decreasing growth rates with increasing germanium content at high temperatures, increasing growth rates with increasing germanium content at low the temperatures, and a maximum of the growth rate with increasing germanium content at intermediate temperature ranges. A two-dimensional model of a low-pressure chemical vapor deposition (LPCVD) reactor is developed so that relationships between epitaxial thin film properties and processing environments can be obtained. The model includes three regions, the entry length region. the annular region, and the inter-wafer one. Experimental data of epitaxial silicon thin films from dichlorosilane obtained in the Purdue LPCVD reactor are seen to be in satisfactory agreement with our theoretical predictions. Simulation results of the Si1-xGex, growth in the Purdue reactor result in deposition rates on the order of about 0.01-0.1 mu m/min at the conditions investigated.