Epitaxial films heteroepitaxy

Epitaxial thin films, 24 742 Epitaxy, 22 152, 185. See also Epitaxial growth Heteroepitaxy in FET fabrication, 22 163-164 in HBT fabrication, 22 166, 167 in RTD fabrication, 22 170 silicon purification via, 22 496 197 vitreous silica in, 22 442 Epitaxy crystallization, ion-beam-induced, 14 447-448... 

During the growth of solid solutions (e. g., pseudobinary alloys and doped compounds), the melt composition at the interface can be a function of time, a situation that results in a natural composition gradient in the growth direction. Heteroepitaxy, the growth of an epitaxial film with a composition different from that of the substrate, is more difficult compared with other... 

When an epitaxial film grows on a substrate of the same nature, one deals with homoepitaxy. If the growth occurs on a different substrate, one deals with heteroepitaxy. 

Heteroepitaxial growth of GaN is usually performed on sapphire or SiC (13 % and 3.4% lattice mismatch, respectively, with GaN). Such a lattice mismatch between GaN and these substrates results in a high dislocation density in the epitaxial films. A variety of techniques have been employed in the past to reduce this high dislocation density and one of the common methods has been to engineer the substrate surface to control, and thus inhibit, the formation of threading dislocations. 

The start of heteroepitaxy on porous sdieon was initiated by a Luryi and Suhir paper in 1986 (Luryi and Suhir 1986). They theoretieaUy predicted a possible approach for growing dislocation-fi-ee lattice-mismatched heteroepitaxial layers on small seed pads of lateral dimension L, having a uniform crystal orientation over the entire substrate wafer. It was proposed that when L is smaller than a specific length Lmm, which depends on the lattice misfit as well as the dislocation energy, the entire elastic stress in the epitaxial films will be accommodated without dislocations. Porous Si, studied at that time for dielectric isolation purposes (Imai 1981), was named as a suitable substrate. 

GaAs films 4 GaN films 3 Ge epitaxy 4 Heteroepitaxial film 1 Heteroepitaxy 1 Homoepitaxy 4... 

There are many practical microelectronic device configurations that are based on epitaxial semiconductor thin films. Heteroepitaxial thin films are also used in magnetic recording media, such as computer hard disks an example is described in Section 1.4.4. Epitaxially grown multilayer structures are also used in planar array laser diodes, which serve as optical inter-connnects for short- and medium-range information transfer, and which offer potential for the development of new devices for such applications as solid... 

Kato et al. [163] and Iwata et al. [164] have performed similar studies on ZnO heteroepitaxial layers grown using plasma-assisted MBE and radical-source MBE techniques. Kato et al. [163] used (112 0)a-plane sapphire substrates and high-temperature growth with low-temperature buffer layers for high-quality undoped ZnO epitaxial films. They obtained electron mobilities as high as 120 cm s and... 

Ventrice, C.A., Jr. and Geisler, H. (1999). The growth and structure of epitaxial metal-oxide/metal interfaces, in Thin Films Heteroepitaxial Systems, ed. W.K. Liu, M.B. Santos, Singapore World Scientific, pp. 167-210. 

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. 

Fundamental to forming high quality structures and devices with thin-films of compound semiconductors is the concept of epitaxy. The definition of epitaxy is variable, but focuses on the formation of single crystal films on single crystal substrates. Homoepitaxy is the formation of a compound on itself. Heteroepitaxy is the formation of a compound on a different compound or element, and is much more prevalent. 

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. 

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. ... 

Island growth also occurs with polycrystalline films, but in epitaxy, the islands combine to form a continuous single-crystal film, that is, one with no grain boundaries. In reality, nucleation is much more complex in the case of heteroepitaxy. Nucleation errors may result in relatively large areas, or domains, with different crystallographic orientations. The interfaces between domains are regions of structural mismatch called subgrain boundaries and will be visible in the microstructure. 

In Ref. [257], Sii- Cx alloy films with x< 0.1 were deposited on Si by molecular beam epitaxy (MBE) to use them for the substrates of heteroepitaxial diamond films. It was expected that when x = 4.33%, a perfect lattice match of Sii C c D = 2 3 occurs and the degree of orientational alignment could be improved. An EIOD film, grown to a thickness of 20 pm using the BEN process, successfully resulted in a (100)-oriented film with (100) faces at the film surface, but the FWHM of the (111) XPF was 6°, the same value as when the direct nucleation of diamond was done on Si using BEN. The results of Raman spectroscopy and XRD of the diamond films were not dependent on the x value. It was thus confirmed that the orientational characteristics of the HOD films had no significant dependence on the C content of the Sii C,v layers. This work can be compared with that of Ref. [258], where layers with x= 1.4 and 3.5% were deposited on Si(lOO) by... 

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