ORDERED QUANTUM DOTS - ATOMIC-FORCE MICROSCOPY STUDY OF A NEW SELF-ORGANIZING GROWTH MODE ON GAAS (311)B SUBSTRATES

We present an atomic force microscopy (AFM) study of a new growth mode found in the metalorganic vapor-phase epitaxy of strained InGaAs layers over AlGaAs buffer layers on GaAs (311)B substrates. With increasing InGaAs layer thickness, growth temperature and In composition, a morphological transition occurs from a uniformly modulated InGaAs layer to the formation of well-ordered rows of disk-shaped InGaAs dots buried beneath AlGaAs microcrystals due to lateral mass transport from the buffer layer. The growth. mode is directly imaged at the onset of the transition where buried disks coexist with the initial modulated surface. From these distinct stages of the formation of the AlGaAs microcrystals, i. e., buried InGaAs disks, and their shape observed by AFM, the growth mode and ordering phenomena are discussed in detail.