Optical properties of GaSb/GaAs type-ІІ quantum dots grown by droplet epitaxy

We study the optical properties of GaSb/GaAs type-ІІ quantum dots (QDs) on a GaAs substrate grown by droplet epitaxy. Ga droplets are formed on GaAs and then exposed to Sb flux to be clad by large granular crystals of Sb. Then the sample was annealed at 380 °C to enhance the reaction of Ga droplets with Sb and to evaporate the excess granular layer. In photoluminescence (PL) measurements, the peaks of the QDs and wetting layer (WL) are observed. The PL intensity of the QDs is much stronger than that of the WL, where the ratio IQD/IWL of the integral intensities is about 13.3. The PL peaks shift toward higher energies with increasing excitation energy, suggesting that the band lineups exhibit a type-ІІ staggered alignment. In addition, we investigate the temperature dependences of the PL peak energy and intensity.