Spectroscopic characterization of the evolution of self-assembled CdSe quantum dots

We have investigated the evolution of molecular beam epitaxy (MBE)-grown, C dSe self-assembled quantum dots on ZnSe surfaces using microphotoluminescen ce techniques. Bare CdSe dots at room temperature undergo Ostwald ripening over a time scale measured in days. At the elevated temperatures maintained for MBE growth and dot formation, ripening is expected to progress much fa ster. Capping the dots with a thin ZnSe layer "freezes'' the ripening, allo wing one to sample different stages of the dot evolution and subsequent cha racterization. We have grown eleven samples, each with a different time int erval, or growth interruption, between dot formation and capping; the growt h interruption times ranging from 0 to 300 s, during which the samples were kept at 300 degrees C. Using microphotoluminescence spectroscopy, we have resolved the sharp emission peaks due to individual dots in each sample and , by analyzing the ensemble characteristics, have identified a new regime i n the evolution of CdSe dots. (C) 1998 American Institute of Physics. [S000 3-6951(98)01149-8].