epitaktisk

Epitaktisk, or epitaxial, describes the growth of a crystalline layer on a crystalline substrate in which the deposited material adopts a definite crystallographic relationship to the substrate. The term is used across materials science and semiconductor technology and emphasizes alignment of lattice planes between the film and the substrate.

There are two main categories: homoepitaxy, where the film and substrate are the same material, and heteroepitaxy, where they are different materials. In both cases, the epitaxial layer is intended to have high crystalline quality and a known orientation, often to enable specific electronic, optical, or mechanical properties.

Growth conditions and surface preparation are crucial for epitaxial success. A well-ordered, clean substrate surface, appropriate temperature, and controlled deposition rate promote layer-by-layer growth and reduce defects. Common methods include molecular beam epitaxy (MBE), chemical vapor deposition (CVD), and metal-organic chemical vapor deposition (MOCVD), each used to tailor composition, doping, and thickness at the atomic scale.

Lattice mismatch between film and substrate introduces strain, which can be accommodated up to a critical thickness. Beyond this, misfit dislocations form, relaxing the film but potentially affecting performance. Strain engineering and buffer layers are often employed to manage these effects in devices.

Applications of epitaktisk growth are widespread in electronics and photonics, including semiconductor devices (transistors and lasers), light-emitting diodes, high-electron-mobility transistors, and solar cells. The technique enables precise control of material properties and heterostructures essential for modern microfabrication.