EPITAXIAL-GROWTH OF STRAIN-FREE GE FILMS ON SI SUBSTRATES BY SOLID-PHASE EPITAXY AT ULTRAHIGH PRESSURE

A novel method to solve the thermal mismatch problem in heteroepitaxial growth has been presented, in which an amorphous film deposited on a single-crystal substrate is grown by solid phase epitaxy at ultrahigh pressure. It has been theoretically predicted in such systems as Ge/Si and GaAs/Si that the difference of the thermal expansion coefficient can be compensated by that of elastic strain generated by hydrostatic pressure. Experimentally, it has been found that the residual strain in Ge films on Si substrates is linearly decreased with increase of the pressure during annealing, while the defect density in the film is kept constant. It has been presumed from these results that a strain-free Ge film can be grown on a Si substrate by solid phase epitaxy at 2.5 GPa.