The impact of AsH3 overflow time and indium composition on the formation of self-assembled InxGa1 − xAs quantum dots studied by atomic force microscopy

Abstract

We have performed atomic force microscopy to investigate the effect of various indium compositions and various AsH3 flow times during cooling on the formation of self-assembled In x Ga1 − xAs quantum dots (QDs). The In x Ga1 − xAs QDs were grown by metal-organic chemical vapour deposition using the Stranski-Krastanow (S-K) growth mode. The migration of group III species in the growth of In x Ga1 − xAs QDs is influenced by the AsH3 flow during the cooling period due to the increasing surface population of the active arsenic species. It influences the size and density of the dots on the surface. For various indium compositions, an increase in In x Ga1 − xAs QD density with increasing indium composition is observed. It indicates that the dot density depends on lattice parameters. The dot density is inversely proportional to surface diffusion (ρ ∝ R/D), with D = (2kT/h)/a2 exp(−ED/kT). In the growth of In x Ga1 − xAs QDs using the S-K growth mode, the dots were formed on the surface as the effect of elastic strain relaxation due to the lattice mismatch. Increasing indium composition affects the lattice mismatch of the In x Ga1 − xAs/GaAs QD system, which influences the dot formation on the surface. However, due to the stochastic nature of the nucleation of self-assembled growth, control of the spatial ordering of the QDs has proved to be extremely challenging.