Elastic energy relaxation and critical thickness for plastic deformation in the core-shell InGaAs/GaAs nanopillars

Abstract

We report on the core-shell InGaAs/GaAs nanopillars grown by metal organic chemical vapor deposition on silicon substrates. The core diameter typically amounts to 600 nm, the shell thickness is around 160 nm, and the lattice mismatch amounts to 2% for the 20% In content used in our growth experiments for wurtzite crystal structure. Surprisingly, the transmission electron microscopy studies reveal an excellent crystal quality in the entire pillar with no noticeable defects even though the critical thickness for dislocation formation in GaAs shell is only 10 nm in the thin film case. To explain the observed effect, we develop a theoretical model that is capable of describing a huge increase of the critical thickness for plastic deformation owing to the core-shell geometry.