Epitaxy is a process used in materials science to grow a crystalline layer on a substrate, which is a base material. This technique allows the new layer to have a specific orientation and structure that matches the underlying substrate. Epitaxy is essential in the production of semiconductors, where precise control over the material properties is crucial for device performance. There are different types of epitaxy, including Molecular Beam Epitaxy (MBE) and Metal-Organic Chemical Vapor Deposition (MOCVD). These methods are commonly used to create thin films of materials like silicon or gallium arsenide, which are vital for electronic and optoelectronic devices, such as LEDs and solar cells.