Formation of ZnSe_1−x S_x quantum dots under Volmer–Weber mode

ZnSe1−xS x quantum dots (QDs) grown directly onto GaAs substrates in Volmer–Weber (V–W) mode by low-pressure metallorganic chemical vapor deposition (MOCVD) are investigated. The value of x is determined by the photoluminescence (PL) spectra. The formation of QDs was confirmed by atomic force microscopy (AFM) images. When the growth duration is short, the surface of the substrate is full of pyramid-like dots; while increasing the duration, another kind of dome-like dots with larger size appear. Meanwhile, the density of the dots decreases with increasing growth duration. The above facts are explained systematically taking into account the surface free energy. The PL characteristics of the dots are also assessed. With increasing growth duration, the emission peak of the dots shows an obvious red-shift, which is due to a decrease in quantum confinement effect.