Strained layer superlattice

In this case, the film consists of a periodic arrangement of many layers, as described in Section 2.4. Suppose that the superlattice is composed of alternating homogeneous layers of materials a and 6 of thicknesses Ahg, and Ahh, respectively. The materials in the film each have a mismatch with respect to the substrate these are denoted by Cma and Cmb, respectively. The period of the structure is A and the total number of periods in the film is N ] the total thickness is then h = XN. Differences in the elastic properties of the two materials with respect to each other and with respect to the substrate are neglected. 

The energy of formation of a misfit dislocation at distance p from the free surface is again given by (6.7) or (6.8). The elastic energy extracted from the system as the dislocation is formed or, equivalently, the work done by the background mismatch stress field as the dislocation is formed, is obtained by means of a straightforward generalization of (6.13). If the misfit dislocation 

If an effective mismatch is defined by the linear weighting rule as 

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RBS and channeling are extremely useful for characterization of epitaxial layers. An example is the analysis of a Sii-j Gejc/Si strained layer superlattice [3.131]. Four pairs of layers, each approximately 40 nm thick, were grown by MBE on a <100> Si substrate. Because of the lattice mismatch between Sii-jcGe c (x a 0.2) and Si, the Sii-j Ge c layers are strained. Figure 3.51 shows RBS spectra obtained in random and channeling directions. The four pairs of layers are clearly seen in both the Ge and Si... 

Fig. 3.51. RBS spectra of 2.07 MeV He ions back-scattered from a Sii-xdex/Si strained layer superlattice.

Another concept for increasing device speed is the strained layer superlattice (SLS), which consists of alternating layers of semiconductor materials with thickness <10 nm deposited by C VD. These materials have the same crystal structure but different lattice... 

Given the lattice mismatch of InAs (a = 0.606 nm) with InSb (a = 0.648 nm), about 6.5%, defects are expected, or a strained layer superlattice at best. Figure 39 is an XRD pattern for a 41 period InAs/InSb deposit, where each period was 10 cycles of InAs followed by 10 cycles of InSb. The central [111] reflection is near 28° and is quite broad. Superlattices should display satellite peaks at angles corresponding... 

Volume 33 Strained-Layer Superlattices Materials Science and Technology... 

S. T. Picraux, B. L. Doyle, and J. Y. Tsao, Structure and Characterization of Strained-Layer Superlattices... 

Helmersson, U., Todorova, S., Barnett, S.A., Sundgren, J.-E., Market, L.C. and Greene, J.E. (1987), Growth of single-crystal TiN/VN strained-layer superlattices with extremely high mechanical hardness , Journal of Applied Physics, 62, 481-484. 

E. Kasper and F. Schaffler, in Strained-Layer Superlattices Materials Science and Technology, edited by T.P. Pearsall (Academic Press, Boston, 1991), p. 223. 

MBE MD-SLS MESFET molecular beam epitaxy modulation doped strained-layer superlattice metal-semiconductor field effect transistor... 

G. C. Osbourn etal., Principles and Applications of Semiconductor Strained-Layer Superlattices... 

Fig. 4 strained layer superlattice of InAsSbon InSbwith 10 nm layer thickness. Photo courtesy of R. M. Biefeld, Sandia National Laboratories. 

See for example Th. Pearsall ed.. Strained-layer Superlattices - Materials Science and Technology in Semiconductors and Semimetals, Vol. 32, Academic Press, Boston, 1991. 

Edelstein D. C., Tang C. L. and Nozik A. J. (1987), Picosecond relaxation of hot-carrier distributions in GaAs/GaAsP strained-layer superlattices , Appl. Phys. Lett. 51, 48-50. 

Fig. 1. X-ray diffraction from a Cu-Ni strained-layer superlattice grown on Cu(100). The inset figure shows an expanded version of the (200) scattering envelope with the intensity shown on a logarithmic scale to reveal higher-order satellites. The multilayer was 2.4 pm thick.

QW strained layer superlattices of AIGaAs, SiGe or antimonide alloys (out to 16 pm). 

Preparation of Device-Quality Strained-Layer Superlattices... 

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