latticematched

Lattice-matched refers to a relationship between two crystalline materials, typically a substrate and a deposited epitaxial layer, in which their in-plane lattice constants are equal or differ by only a small tolerance. When lattice matching is achieved, the film can grow coherently with minimal strain at the interface, facilitating high-quality crystal continuity across the boundary.

Lattice mismatch is quantified by m = (a_f − a_s)/a_s × 100%, where a_f is the film lattice constant and a_s is the substrate lattice constant. A small |m| indicates lattice matching, while larger values lead to strain and the formation of defects. Even with a lattice-matched pair, differences in thermal expansion can induce residual stress during cooling, and the concept is most relevant to the epitaxial growth regime and device performance.

Measurement and assessment are typically performed using X-ray diffraction and reciprocal-space mapping, along with high-resolution transmission electron microscopy. These techniques determine how well the film lattice aligns with the substrate and reveal any remaining dislocations or defects. Lattice matching guides material selection for heterostructures used in optoelectronics, microelectronics, and nanostructures, where crystal quality directly impacts performance.

Common lattice-matched systems include GaAs on GaAs, and GaAs grown on relaxed AlGaAs alloys, where the aluminum content is chosen to achieve the same in-plane lattice constant as GaAs. Other lattice-matched pairings exist in the III-V family and in the InP system, with specific compositions engineered to minimize strain.

In practice, lattice matching is a key design criterion in epitaxial growth methods such as molecular beam epitaxy and metal-organic chemical vapor deposition, enabling high-quality quantum wells, lasers, detectors, and high-electron-mobility devices.