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-ultravi olet-excited chemical-vapor deposition from GeH4 are relieved in diffe rent ways depending on growth temperature. At temperatures below 190 d egrees C, stacking faults and amorphous Ge embedded over the crystalli ne film accommodate the misfit strains. Between 230 and 310 degrees C, two-dimensional Ge epilayers with abrupt interfaces and numerous thre ading dislocations grow. Above 350 degrees C, the misfit strains are r elaxed mainly by the roughening of the Ge/Si interface, thus, decreasi ng the dislocation density. The surfactant effect of H atoms controls the film morphology. To obtain a uniform Ge epitaxial film with atomic ally sharp interfaces, the optimum temperature is 270-300 degrees C an d the GeH4 gas pressure is 1-3 X 10(-3) Torr. (C) 1998 Elsevier Scienc e B.V. All rights reserved.