Heteroepitaxial deposition

Similarly, the defect structure associated with surface-reconstruction phenomena is known to exert an influence on heteroepitaxial deposition. This has been demonstrated for both lead and nickel deposition on reconstructed Au(lll) [353,360,451]. For nickel deposition, nucleation was observed to proceed in three distinct, potential-dependent steps [354,451]. At... 

In this section we are concerned with epitaxial deposition. The word Greek taxis can mean an arrangement or a positioning. The Greek preposition epi in this context means upon. Epitaxial, then, means that the deposited layers are arranged on something namely, the substrate or layers already deposited. The particular arrangement is crystalline. The term epitaxial deposition is reserved for crystalline deposition. Epitaxial is further refined to include homoepitaxial and heteroepitaxial. In homoepitaxial deposition, the deposited material is the same as the substrate silicon on silicon and diamond on diamond are examples of homoepitaxial deposition. In heteroepitaxial deposition the deposited material is different from the substrate diamond on silicon or GaN on sapphire. 

Owing to the high supersaturation achievable in most CVD processes, they are well suited for heteroepitaxial deposition. Meltback, or substrate dissolution, frequently posing problems in the presence of a liquid phase, does not occur. 

This article focuses primarily on the properties of the most extensively studied III—V and II—VI compound semiconductors and is presented in five sections (/) a brief summary of the physical (mechanical and electrical) properties of the 2incblende cubic semiconductors (2) a description of the metal organic chemical vapor deposition (MOCVD) process. MOCVD is the preferred technology for the commercial growth of most heteroepitaxial semiconductor material (J) the physics and (4) apphcations of electronic and photonic devices and (5) the fabrication process technology in use to create both electronic and photonic devices and circuits. 

The nature of the deposit and the rate of nucleation at the very beginning of the deposition are affected, among other factors, by the nature of the substrate. A specific case is that of epitaxy where the structure of the substrate essentially controls the structure of the deposit.Plb lP ] Epitaxy can be defined as the growth of a crystalline film on a crystalline substrate, with the substrate acting as a seed crystal. When both substrate and deposit are of the same material (for instance silicon on silicon) or when their crystalline structures (lattice parameters) are identical or close, the phenomena is known as homoepitaxy. When the lattice parameters are different, it is heteroepitaxy. Epitaxial growth cannot occur if these stmctural differences are too great. 

Lincot D, Mokili B, Cortes R, Froment M (1996) Heteroepitaxy of chemically deposited CdS on mismatched (111) GaP. Microsc Microanal Microstruct 7 217-224... 

The rapid developments in the microelectronics industry over the last three decades have motivated extensive studies in thin-film semiconductor materials and their implementation in electronic and optoelectronic devices. Semiconductor devices are made by depositing thin single-crystal layers of semiconductor material on the surface of single-crystal substrates. For instance, a common method of manufacturing an MOS (metal-oxide semiconductor) transistor involves the steps of forming a silicon nitride film on a central portion of a P-type silicon substrate. When the film and substrate lattice parameters differ by more than a trivial amount (1 to 2%), the mismatch can be accommodated by elastic strain in the layer as it grows. This is the basis of strained layer heteroepitaxy. 

The surface cleaning of the CIS also affected the mode of deposition of the CdS. The CdS was found to grow to a greater or lesser extent of epitaxy on single-crystal (heteroepitaxial layer) CIS [22]. Very good epitaxy of cubic CdS was found for cyanide-treated CIS somewhat lower epitaxy was found for ammonia-treated surfaces and poorer epitaxy obtained for untreated surfaces that contained considerable oxides. Additionally, the epitaxy was only obtained at higher deposition temperatures (>70°C) at lower temperatures, the growth was polycrystalline. 

Heteroepitaxy. Heteroepitaxy (e.g., deposition of Al Ga As on GaAs) is somewhat different, because the solid and liquid cannot initially be in equilibrium, that is, a chemical potential difference exists across the solid-liquid interface. In compound semiconductors, the chemical potential of each element is constrained by compound stoichiometry. For example, for a ternary solid (A B C) in equilibrium with a ternary liquid, the conditions of equilibrium are given by equations 8 and 9 ... 

In molecular beam epitaxy (MBE) [317], molecular beams are used to deposit epitaxial layers onto the surface of a heated crystalline substrate (typically at 500-600° C). Epitaxial means that the crystal structure of the grown layer matches the crystal structure of the substrate. This is possible only if the two materials are the same (homoepitaxy) or if the crystalline structure of the two materials is very similar (heteroepitaxy). In MBE, a high purity of the substrates and the ion beams must be ensured. Effusion cells are used as beam sources and fast shutters allow one to quickly disrupt the deposition process and create layers with very sharply defined interfaces. Molecular beam epitaxy is of high technical importance in the production of III-V semiconductor compounds for sophisticated electronic and optoelectronic devices. Overviews are Refs. [318,319],... 

Epitaxy The deposition of a single-crystal film of a material upon a template of atoms provided by the surface of a crystalline solid called the substrate. Such a film is termed an epitaxial layer If the film and substrate are composed of materials having the same lattice parameter, the film is homoepitaxial," and if the film and substrate are formed from materials with different lattice parameters, the film is heteroepitaxial. ... 

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