Mechanism of strain relaxation by twisted nanocolumns revealed in AlGaN/GaN heterostructures

V P Kladko,A E Belyaev,S A Vitusevich,A V Kuchuk,H Hardtdegen,V F Machulin,N V Safryuk

doi:10.1063/1.3184569

Abstract

The structural properties of AlGaN/GaN heterostructures grown by metal organic chemical vapor deposition on sapphire substrates with different thicknesses were studied by high-resolution x-ray diffraction. The relation between the deformations and dislocation densities in the layer and substrate was established. The dependence of the system’s curvature on the lattice mismatch, caused by different fractions of nanoblock twists with respect to the c-plane, was determined. A mechanism of elastic strain relaxation was proposed.

Highlights

Up to now, the physical mechanism explaining the features in the mosaic structure of III-V alloys has not been established, which has considerably delayed progress in this field of research
In order to solve the problem, the influence of the deformation state on the structural and electrical properties of multilayered nitride heterostructures, on their mosaic structure as well as on defects caused by processes of elastic strain relaxation needs to be studied in detail
We investigate the influence of dislocationsdislocation density, type of dislocations, and the law of their distributionon the deformation conditions of AlxGa1−xN / GaN heterostructures grown on substrates with different thicknesses

Summary

Introduction

X-ray diffractionXRDis the most effective method of obtaining structural parameters, the magnitude of elastic strain deformation, and the composition of the nitride structures.5 In this letter, we investigate the influence of dislocationsdislocation density, type of dislocations, and the law of their distributionon the deformation conditions of AlxGa1−xN / GaN heterostructures grown on substrates with different thicknesses. The mismatch of planes in heterostructures is caused by the twist of the corresponding layers with respect to the substrate and each other.

Results

Conclusion