Optimum conditions for producing abrupt interfaces in vacuum-ultraviolet-excited Ge epitaxy on Si 100/

Misfit strains in Ge films grown on Si 100.by means of vacuum-ultraviolet-excited chemical-vapor deposition from GeH4 are relieved in different ways depending on growth temperature. At temperatures below 1908C, stacking faults and amorphous Ge embedded over the crystalline film accommodate the misfit strains. Between 230 and 3108C, two-dimensional Ge epilayers with abrupt interfaces and numerous threading dislocations grow. Above 3508C, the misfit strains are relaxed mainly by the roughening of the GerSi interface, thus, decreasing the dislocation density. The surfactant effect of H atoms controls the film morphology. To obtain a uniform Ge epitaxial film with atomically sharp interfaces, the optimum temperature is 270–3008C and the GeH4 gas pressure is 1–3=10y3 Torr. q1998 Elsevier Science B.V. All rights reserved.