Surface smoothing of SiGe strain-relaxed buffer layers by chemical mechanical polishing

We flattened the rough surface of the strain-relaxed Si0.7Ge0.3 buffer layers by chemical mechanical polishing technique and successfully obtained the ultra-smooth surface whose root mean square roughness was less than 1 nm. The regrowth of Si0.7Ge0.3 films on the polished Si0.7Ge0.3 buffer layer was found to keep its surface roughness less than 1 nm, and efficient photoluminescence with narrow line width was observed from quantum wells grown on the polished buffer layer. This indicates high crystalline quality of the regrown layer with smooth interfaces, which makes it possible to fabricate high-performance SiGe devices with low surface roughness scattering.