Strain relaxation and self-organizing MBE-growth of local SiGe-structures

SiGe wires and dots of μm size were fabricated by a self-organizing MBE growth mode. Layer thickness and Ge content on top of a Si mesa buffer are varied. It is shown that defect free growth exceeding the critical thickness is possible for locally grown mesa structures. Raman spectroscopy exhibits reduced strain relaxation for decreasing lateral dimensions. The SiGe-growth on the top of a locally grown Si buffer layer results in the nucleation of dislocations mainly in the Si buffer. This effect of defect accumulation in the locally grown buffer offers a method for the fabrication of relaxed, defect free virtual substrates.