CdSe/ZnSe Quantum Dots Formed by Low Temperature Epitaxy and In-Situ Annealing: Properties and Growth Optimization

The formation of CdSe/ZnSe quantum dots by a method combining a low temperature MBE growth of a CdSe layer and its subsequent in-situ annealing at temperatures between 280-340ºC has been studied. The thermal treatment results in a re-organization of the surface from a nearly two-dimensional layer to an ensemble of three-dimensional dot-like features. In this work we optimized the different growth and annealing parameters of this process and compared the properties of the resultant dots with those of dots grown by conventional MBE at 300ºC. It is demonstrated that the luminescence properties of the dots for both growth techniques are comparable but the areal density achieved by the in-situ annealing technique is an order of magnitude lower. From high resolution X-ray diffraction results, it could be established that no desorption takes place despite significantly long annealing duration. Beyond a nominal coverage of 3.5 ML CdSe, stacking faults are generated, leading to a gradual decrease in luminescence intensities and an overlap of pendellösung fringes in X-ray diffractograms.