Semiconductors molecular beam epitaxy

Chemical Vapor Deposition Crystal Growth Molecular Beam Epitaxy, Semiconductors Ex-citons, Semiconductor Lasers, Semiconductor Molecular Beam Epitaxy, Semiconductors... 

Epitaxial crystal growth methods such as molecular beam epitaxy (MBE) and metalorganic chemical vapor deposition (MOCVD) have advanced to the point that active regions of essentially arbitrary thicknesses can be prepared (see Thin films, film deposition techniques). Most semiconductors used for lasers are cubic crystals where the lattice constant, the dimension of the cube, is equal to two atomic plane distances. When the thickness of this layer is reduced to dimensions on the order of 0.01 )J.m, between 20 and 30 atomic plane distances, quantum mechanics is needed for an accurate description of the confined carrier energies (11). Such layers are called quantum wells and the lasers containing such layers in their active regions are known as quantum well lasers (12). 

Electrical Properties. Generally, deposited thin films have an electrical resistivity that is higher than that of the bulk material. This is often the result of the lower density and high surface-to-volume ratio in the film. In semiconductor films, the electron mobiHty and lifetime can be affected by the point defect concentration, which also affects electromigration. These effects are eliminated by depositing the film at low rates, high temperatures, and under very controUed conditions, such as are found in molecular beam epitaxy and vapor-phase epitaxy. 

An important method for producing semiconductor layers is the so-called molecular beam epitaxy (MBE) (see [3,12-14] and [15-19]). Here, atoms of the same or of a different material are deposited from the vapor source onto a faceted crystal surface. The system is always far from thermal equilibrium because the deposition rate is very high. Note that in this case, in principle, every little detail of the experimental setup may influence the results. 

Optoelectronics is a relatively new and fast-growing industry with many applications. Thin-film processes, such as reactive sputtering, molecular-beam epitaxy (MBE), and particularly MOCVD, play a major part in their production. Equipment and materials are similar to those used in the semiconductor industry and many companies manufacture both types of products. In fact the distinction between the two areas is often blurred. Statistics generally do not single out optoelectronics as such and, for that reason, it is difficult to define the scope of the industry accurately. 

The results of the ellipsometric study are presented in Table 9. As is clear from the table, the resultant average thickness of the semiconductor layer, obtained from one bilayer precursor, is about 0.8 nm. This value can be considered the thickness resolution of this technique. It is worth mentioning that among the available techniques, only molecular beam epitaxy allows one to reach such resolution. However, the proposed technique is much simpler and does not require complicated or expensive equipment. 

Summarizing, it is possible to conclude that the technique of forming ultrasmall semiconductor particles turned out to be a powerful tool for building up single-electron junctions, even working at room temperature, as well as thin semiconductor layers and superlattices with structural features, reachable in the past only via molecular beam epitaxy. 

McPhail (1989) gives a detailed account of the experimental approach to depth profiling of semiconductors, including the quantification of the data. He illustrates the analysis of a silicon epilayer grown by molecular beam epitaxy (MBE) in which 11 boron-rich layers were incorporated by co-evaporation of boron. The intended structure is shown in Figure 4.8, and it was desirable to establish the concentration of boron in the layers, the inter-peak concentration and the sharpness of the doping transitions. 

MBE (molecular beam epitaxy), which involves epitaxial growth of thin films on either the same material as substrate (homoepitaxial) or a lattice-matched substrate (heteroepitaxial) the heated substrate reacts with a molecular beam of compounds containing the constituent elements of the semiconductor as well as any dopants the resultant film is essentially a single crystal slow growth rates produce films from a few nanometers thick to at most several hundred nanometers that have very high purity and controlled levels of dopants. 

Dale L. Martin, Molecular Beam Epitaxy of IV-VI Compound Heterojunctions Robert L. Gunshor, Leslie A. Kolodziejski, Arto V. Nurmikko, and Nobuo Otsuka, Molecular Beam Epitaxy of II-VI Semiconductor Microstructures... 

Molecular beam epitaxy (MBE) is an expensive yet widely used technique for producing epitaxial layers of metals, insulators and III-V and II-VI based semiconductors, both at the research and the industrial production level (Herman, 1996). It consists of deposition of molecular beams of atoms or clusters of atoms, which are produced by heating up a solid source, onto a heated crystalline substrate in ultra-high vacuum. MBE is characterized by low growth temperatures and low growth rates and thus enables producing high-precision epitaxial structures with monolayer... 

Quantum dots are the engineered counterparts to inorganic materials such as groups IV, III-V and II-VI semiconductors. These structures are prepared by complex techniques such as molecular beam epitaxy (MBE), lithography or self-assembly, much more complex than the conventional chemical synthesis. Quantum dots are usually termed artificial atoms (OD) with dimensions larger than 20-30 nm, limited by the preparation techniques. Quantum confinement, single electron transport. Coulomb blockade and related quantum effects are revealed with these OD structures (Smith, 1996). 2D arrays of such OD artificial atoms can be achieved leading to artificial periodic structures. 

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