US Patent 7666799 Epitaxial growth of relaxed silicon germanium layers

A relaxed silicon germanium structure comprises a silicon buffer layer produced using a chemical vapor deposition process with an operational pressure greater than approximately 1 torr. The relaxed silicon germanium structure further comprises a silicon germanium layer deposited over the silicon buffer layer. The silicon germanium layer has less than about 107 threading dislocations per square centimeter. By depositing the silicon buffer layer at a reduced deposition rate, the overlying silicon germanium layer can be provided with a “crosshatch free” surface.