Structural investigation of growth and dissolution of InxGa1-xNInxGa1-xN nano-islands grown by molecular beam epitaxy

Free-standing nanometre sized InxGa1-xNInxGa1-xN islands and islands capped with thin GaN layers were grown by molecular beam epitaxy (MBE) and characterised by high resolution transmission electron microscopy (HRTEM). By adjusting the growth temperature of the InxGa1-xNInxGa1-xN islands, deposition of the wurtzite modification was realised. The obtained free-standing islands are plastically relaxed by approximately equidistant misfit dislocations. For capped samples, the GaN cap layer thickness was varied between nominal thicknesses of 2 nm and 8 nm. Already for a 2 nm thick cap layer, strong dissolution of the islands occurred. In case of the 8 nm thick GaN cap layer, all former islands are dissolved, and an InGaN layer of approximately homogeneous indium concentration is observed.