LOW-TEMPERATURE EPITAXIAL-GROWTH OF GE USING ELECTRON-CYCLOTRON-RESONANCE PLASMA-ASSISTED CHEMICAL VAPOR-DEPOSITION

Epitaxial Ge films have been deposited on Si and Ge substrates at 300-degrees-C using electron-cyclotron-resonance plasma-assisted chemical vapor deposition. Helium was fed into the resonance chamber, and a mixture of helium and germane were fed downstream at a location above the substrate. Surface roughness increased with energetic ion bombardment as quantified by the number of ions striking the surface per Ge atom deposited. Surface roughness also increased with increasing substrate temperature. Films with very rough surface morphology were found to be polycrystalline. The large hydrogen content of the films, particularly those deposited on Si, appeared to prevent the reduction of the epitaxial temperature below 300-degrees-C. In the temperature range between 300 and 325-degrees-C, hydrogen bubbles formed at the Ge/Si interface and caused the films to pucker from the surface. Increasing the substrate temperature above 325-degrees-C eliminated this problem by decreasing the surface coverage of hydrogen during deposition.