SiGe nanostructures by selective epitaxy and self-assembling

There is increasing interest in Si-based optoelectronics using Si1−xGex nanostructures due to the possibility of their integration with the Si technology. To overcome the problem of the indirect character of SiGe one is looking for solutions to improve the carrier confinement and collection efficiency by realizing structures involving quantum-size effects. Several fabrication strategies for semiconductor nanostructures have been proposed. One possible approach involves selective epitaxy to fill-in the small holes in patterned substrates. To realize the lateral confinement below 100 nm the patterned substrates are made either by e-beam lithography or by optical lithography. In the latter case, the sub-100 nm confinement is realized using the development of facets. Another approach for nanostructures is based on self-assembling which leads to island formation in highly lattice-mismatched layers. These items will be discussed for SiGe as well as device applications such as light emitting diodes with Ge islands.