We have presented the study result of physical and optical properties of the InCaAs quantum ring (QR) structures grown by droplet epitaxy using molecular beam epixaty. The structural properties and quality of QRs strongly depended on In0.5Ga0.5 droplet amount. The photoluminescence (PL) results confirmed the crystal quality of the nanocrystal of the capped samples with the optimum In0.5Ga0.5 droplet amount. The optimum In0.5Ga0.5 amount is 3 and 4 ML (monolayer) under the droplet forming condition of 210 degrees C substrate and crystallization at 180 degrees C. The PL measuring parameters, including excitation intensity and polarization, have been varied. The polarized PL spectra indicated anisotropy in the QR structures. (C) 2010 Elsevier B.V. All rights reserved.