A novel thin buffer concept for epitaxial growth of relaxed SiGe layers with low threading dislocation density

We demonstrate an approach for fabricating relaxed SiGe layers on Si substrate with low threading dislocation density using commercially available low-pressure chemical vapor deposition epitaxy systems. This approach involves a thin epitaxial buffer layer with a reversed Ge composition gradient, i.e., the Ge composition decreases from the Si substrate to the growing surface. On a 90 nm thick buffer, growth of SiGe layer with composition up to 32% Ge was demonstrated with a strain relaxation >80% and a threading dislocation density below 10 ⁶ cm ^-2.