Atomically controlled Ge epitaxial growth on Si(1 0 0) in Ar-plasma-enhanced GeH₄ reaction

Ar-plasma-enhanced GeH₄ reaction using an ultraclean electron cyclotron resonance (ECR) plasma apparatus is investigated, and atomically flat Ge epitaxial growth on Si(1 0 0) is achieved even without substrate heating. It is found that the crystallinity degradation of deposited Ge film is caused by incorporation of Ar into the film under Ar plasma irradiation. The Ar incorporation could be suppressed by lowering substrate surface temperature as well as incident Ar ion energy. The Ge film has large compressive in-plane strain and relaxes by heat treatment at 600 °C. These results open the way to atomically controlled Ge epitaxial growth at very low temperature.