The fabrication of nanometer-scale GaAs dots on AlGaAs layer by molecular b
eam epitaxy was demonstrated. Unlike the stress-driven transition of the th
ree-dimensional growth mode in the lattice-mismatched system, the limited m
igration of Ga droplets on the AlGaAs layer grown at low substrate temperat
ure was exploited to give rise to the formation of three-dimensional GaAs i
slands. The resulting GaAs dots show crater-like features having {111} face
ts. In micro-photoluminescence measurements of the buried structures, the e
mission spectra were clearly observed, and the sharp lines of the spectra m
ight be considered as the exciton emissions from individual dots with vario
us sizes.