FIGURE 1 Strained-layer superlattice (SLS): schematic cross section showing substrate, buffer layer, and superlattice.

mismatch). SLSs are typically made from the more common Group III–V compound semiconductors such as InAsSb, GaAsP, or InGaAs.

The multiple thin layers may be viewed macroscopically as a new semiconductor material (material X). The combination of the thin layers and lattice strain allow flexibility in tailoring the properties of material X. The properties that may be controlled include the energy bandgap, direct-indirect bandgap, effective mass-velocity field characteristics, and average lattice constant.

The energy bandgap of an SLS can be controlled by changing either the type of material or the thickness of the layers or both. The effect is akin to the behavior of the particle-in-box solution to the Schrödinger wave equation, that is, thin layers increase the energy ground state.