Epitaxial growth is a technology that grows a single crystal layer on a single crystal substrate (substrate) with the same crystal orientation as the substrate, as if the original crystal has extended outward. This newly grown single crystal layer can be different from the substrate in terms of conductivity type, resistivity, etc., and can grow multi-layer single crystals with different thicknesses and different requirements, thus greatly improving the flexibility of device design and device performance. In addition, the epitaxial process is also widely used in PN junction isolation technology in integrated circuits and in improving material quality in large-scale integrated circuits.
The classification of epitaxy is mainly based on the different chemical compositions of the substrate and epitaxial layer and the different growth methods.
According to different chemical compositions, epitaxial growth can be divided into two types:
1. Homoepitaxial: In this case, the epitaxial layer has the same chemical composition as the substrate. For example, silicon epitaxial layers are grown directly on silicon substrates.
2. Heteroepitaxy: Here, the chemical composition of the epitaxial layer is different from that of the substrate. For example, a gallium nitride epitaxial layer is grown on a sapphire substrate.
According to different growth methods, epitaxial growth technology can also be divided into various types:
1. Molecular beam epitaxy (MBE): This is a technology for growing single crystal thin films on single crystal substrates, which is achieved by precisely controlling the molecular beam flow rate and beam density in ultra-high vacuum.
2. Metal-organic chemical vapor deposition (MOCVD): This technology uses metal-organic compounds and gas-phase reagents to perform chemical reactions at high temperatures to generate the required thin film materials. It has wide applications in the preparation of compound semiconductor materials and devices.
3. Liquid phase epitaxy (LPE): By adding liquid material to a single crystal substrate and performing heat treatment at a certain temperature, the liquid material crystallizes to form a single crystal film. The films prepared by this technology are lattice-matched to the substrate and are often used to prepare compound semiconductor materials and devices.
4. Vapor phase epitaxy (VPE): Utilizes gaseous reactants to perform chemical reactions at high temperatures to generate the required thin film materials. This technology is suitable for preparing large-area, high-quality single crystal films, and is especially outstanding in the preparation of compound semiconductor materials and devices.
5. Chemical beam epitaxy (CBE): This technology uses chemical beams to grow single crystal films on single crystal substrates, which is achieved by precisely controlling the chemical beam flow rate and beam density. It has wide applications in the preparation of high-quality single crystal thin films.
6. Atomic layer epitaxy (ALE): Using atomic layer deposition technology, the required thin film materials are deposited layer by layer on a single crystal substrate. This technology can prepare large-area, high-quality single crystal films and is often used to prepare compound semiconductor materials and devices.
7. Hot wall epitaxy (HWE): Through high-temperature heating, gaseous reactants are deposited on a single crystal substrate to form a single crystal film. This technology is also suitable for preparing large-area, high-quality single crystal films, and is especially used in the preparation of compound semiconductor materials and devices.
Post time: May-06-2024