Epitaxí

Epitaxy is a process in materials science where a thin film of crystalline material is grown on a crystalline substrate. The key characteristic of epitaxy is that the crystalline structure of the film aligns with the crystalline structure of the substrate. This alignment occurs because the substrate's surface acts as a template for the growing film, dictating the orientation and arrangement of atoms in the new layer.

There are two primary types of epitaxy. Homoepitaxy involves growing a film of the same material as the substrate, such as silicon on silicon. This is often used to create purer or defect-free layers on a commercially available substrate. Heteroepitaxy, on the other hand, involves growing a film of a different material than the substrate, like gallium arsenide on silicon. This allows for the combination of different material properties to create novel devices.

The epitaxy process typically takes place in a vacuum chamber under controlled temperature and pressure. Various techniques are employed, including molecular beam epitaxy (MBE) and chemical vapor deposition (CVD). MBE involves the precise deposition of atomic or molecular beams onto the substrate, offering high control over film composition and thickness. CVD uses gaseous precursors that react on the heated substrate surface, forming the solid crystalline film.

Epitaxy is a crucial technique in the fabrication of a wide range of electronic and optoelectronic devices, including transistors, integrated circuits, light-emitting diodes (LEDs), and lasers. The ability to precisely control the crystalline structure and composition of thin films is fundamental to achieving the desired electrical and optical properties required for these advanced applications.