Fabrication of High Quality SiGe Virtual Substrates by Combining Misfit Strain and Point Defect Techniques

High quality strain-relaxed thin SiGe virtual substrates have been achieved by combining the misfit strain technique and the point defect technique. The point defects were first injected into the coherently strained SiGe layer through the "inserted Si layer" by argon ion implantation. After thermal annealing, an intermediate SiGe layer was grown with a strained Si cap layer. The inserted Si layer in the SiGe film serves as the source of the misfit strain and prevents the threading dislocations from propagating into the next epitaxial layer. A strained-Si/SiGe/inserted-Si/SiGe heterostructure was achieved with a threading dislocation density of 1×10⁴ cm^-2 and a root mean square surface roughness of 0.87 nm. This combined method can effectively fabricate device-quality SiGe virtual substrates with a low threading dislocation density and a smooth surface.