3.1.2 Applications of Strain

The study of lattice-mismatched epitaxy gained much attention when it was recognized that strained-layer structures might display new electronic and optical properties not seen in the unstrained-constituent materials [3,56]. The strain is unavoidable in semiconductor heterostructures. However it can be a tool for modifying the band structure of semiconductors in a useful and predictable fashion. The strain is imposed internally, as a consequence of lattice-mismatch and it may be compressive or tensile. To modify the band structure by more than 100 meV it is necessary to create a lattice mismatch greater than about 2%. This in turn means that a careful control over the layer thickness is required to produce extended strained structures that meet the critical thickness requirement. S. Smirnov: