Cross-sectional Transmission Electron Microscopy of (AlAs)15(InAs)1 Superlattices

1990 ◽  
Vol 48 (4) ◽  
pp. 678-679
Author(s):  
C. Ballesteros ◽  
J. Piqueras ◽  
M. Vázquez ◽  
J.P. Silveira ◽  
L. González ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Atomic Layer ◽  
Growth Conditions ◽  
Layer By Layer ◽  
High Quality ◽  
Cross Sectional ◽  
Strained Layer ◽  
Transmission Electron ◽  
Strained Layer Superlattices

Multibeam and bright field transmission electron microscopy are used to determine the structure of (InAs)1/(AlAs)15 superlattices. The interest of InAs/AlAs system arises from the large gap difference. The main problem in the obtention of strained layer superlattices (SLS), with a large lattice mismach, 7% is that of controlling the growth process to obtain high quality layers with sharp interfaces.A modification of the conventional MBE technique, Atomic Layer Molecular Beam Epitaxy (ALMBE) seems to be very appropiate for the growth of such strained layer structures. In particular, high quality layers of materials that demand different growth conditions by MBE, like InAs and AlAs can be obtained at a common low substrate temperature (350-400°) by ALMBE due to the ability to force 2D or layer by layer nucleation and growth. Present superlattices are part of a series with structure (AlAs)15/(InAs)n (n = 1, 2, 3 and 5 ml) whose study by HREM is under way in order to determine critical thickness limits.

The Mechanisms of Relaxation in Strained Layer GeSi/Si Superlattices: Diffusion Vs. Dislocation Formation

1987 ◽  
Vol 103 ◽  
Author(s):  
F. K. LeGoues ◽  
S. S. Iyer ◽  
K. N. Tu ◽  
S. L. Delage
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Cross Sectional ◽  
Strained Layer ◽  
Enhanced Diffusion ◽  
Transmission Electron ◽  
Through Diffusion ◽  
Strained Layer Superlattices ◽  
Plane View ◽  
Dislocation Formation

ABSTRACTSixGe1−x strained layer superlattices are known to be metastable in that they can be grown fully commensurate with layer thickness higher than the equilibrium, calculated Tc at which dislocation formation becomes energetically favorable. In this paper, we describe the mechanism of relaxation in such multilayers. Both plane-view and cross-sectional transmission electron microscopy (TEM) were used to examine the formation of dislocation at the different interfaces. RBS was used to follow interdiffusion. We found two competing mechanisms for relaxation: The preferred mode for relaxation is the creation of dislocation networks at each of the interfaces. This process can be stopped or considerably inhibited by the difficulty of forming new dislocations in samples which are perfectly commensurate after growth; Some dislocations appear necessary in order to generate more dislocations during annealing. When this is not the case, the only possible way to attain relaxation is through diffusion. In such a case, stress-enhanced diffusion is observed, with a diffusion coefficient 200 times higher than expected.

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