Nanoscale InGaAs concave disks fabricated by heterogeneous droplet epitaxy

The detailed cross-sectional structure of InGaAs quantum dots fabricated by a heterogeneous droplet epitaxy method was investigated by means of cross- sectional transmission electron microscopy observation. It was confirmed th at concave disks without any dislocations or wetting layer were formed at t he upper part of the flat surface. This result was consistent with the chan ge of photoluminescence intensity and peak position. The sizes of the disks were estimated to be 30 and 12 nm in lateral and vertical directions, resp ectively. From this estimation, the occurrence of a phase-separation effect is suggested. (C) 2000 American Institute of Physics. [S0003-6951(00)01724 -1].