We have fabricated highly packed and ordered In0.4Ga0.6As quantum dots (QDs
) array on GaAs(311)B substrate without coalescence of QDs. Reflection high
-energy electron diffraction and Auger spectra suggest the inhomogeneous di
stribution of In and Ga in QD. In concentration near the surface of QD is l
arger than that of the inside, and the inhomogeneous distribution of In and
Ga in QDs prevents QDs from merging. (C) 1998 American Institute of Physic
s. [S0003-6951(98)01349-7].