Abstract
Two hetero structures with the step-graded buffers of different design grown on (001) GaAs substrates by molecular beam epitaxy were employed to reveal applicability of an extension of phenomenological approach developed for the description of strain relief in single layer hetero structures to multilayer thin film systems. Difference in the design of buffers provided to the formation of dislocation free layers of different thickness. The determination of the residual strains in the epitaxial layers was done using reciprocal space mapping performed with a tripleaxes X-ray diffractometer Smart Lab 9 kW and the following processing of data obtained within the linear theory of elasticity. It was established that, despite the different design of buffers the character of strain spatial distributions in them was similar. It gives possibility to attract a phenomenological rule to describe the strain relief in the final constructive elements of both hetero structures. A correction for a work hardening in the phenomenological rule governing the strain relief in single layer hetero structures was performed.
Highlights
IntroductionHetero structures applied to ultrahigh frequency (UHF) electronics devices (for example, high electron mobility transistors–HEMTs) are created, as a rule, on a single crystal substrate GaAs of (001) This model considered MM-buffer with a continuous increasing orientation and consist of a metamorphic (MM) buffer aiming to lattice misfit due to the increase of the concentration of an remove a mismatch between the substrate and device active alloying element
The MM-buffer may the formation of dislocation free layer at the top region of buffer have a different design, for example, it may be step-graded [1- gives an energetic gain for the system [3,4,5,6]
The performed study gives some evidence concerning the possibility of numerical description of a value of strain in the dislocation free layer of the step-graded MM-buffer in the framework of the phenomenological approach developed for single layer hetero structures. This description has a quadratic form as an inverse proportion between the residual compressive stain in the dislocation free layer and the root square of the layer thickness
Summary
Hetero structures applied to ultrahigh frequency (UHF) electronics devices (for example, high electron mobility transistors–HEMTs) are created, as a rule, on a single crystal substrate GaAs of (001) This model considered MM-buffer with a continuous increasing orientation and consist of a metamorphic (MM) buffer aiming to lattice misfit due to the increase of the concentration of an remove a mismatch between the substrate and device active alloying element. When moving this system to the equilibrium, layers including a quantum well (QW).
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