Growth mechanism of InAs quantum dots on GaAs by metal-organic chemical-vapor deposition

The growth parameters affecting the deposition of InAs quantum dots (QDs) by metal-organic chemical-vapor deposition are reported. Experiments with arsine pause, gas switching, and hydrogen shroud flow show that a low V/III ratio is the key to obtaining three-dimensional InAs island formation with high density and uniformity. Based on atomic force microscopy images of InAs QDs deposited under different growth conditions, a physical model for the epitaxial growth of three-dimensional islands is proposed. In this model, the InAs QD growth is governed by two types of arsenic sources at the growth surface: free arsenic atoms arriving at the boundary layer and dangling arsenic bonds available at the GaAs wafer surface. At high V/III ratio, free arsenic atoms arriving at the boundary layer are the dominant hydride species and produce a low density of InAs islands with irregular shape and polycrystalline defects. At low V/III ratio arsenic bonds on the GaAs surface are the main sites for indium atoms to attach to, thus producing high island densities and small coherent island sizes. (C) 2005 American Institute of Physics.