CdS quantum dots ͑QDs͒ were formed on ZnSe and ZnS x Se 1Ϫx . The nucleation process was monitored by reflection high energy electron diffraction, and it was suggested that QDs were formed without the wetting layer. The low temperature ͑13 K͒ photoluminescence ͑PL͒ measurement showed that the peak energy could be controlled by the amount of the CdS deposit. The PL peak energy covered most of visible range, indicating that the band lineup between CdS QD and ZnSe ͑or ZnS x Se 1Ϫx ) host would be type II. Bright green and blue light emitting diode ͑LED͒ structures were fabricated in which CdS QDs were embedded in pn junctions of ZnSe and ZnS x Se 1Ϫx . The control of QD size as well as the band gap of the host material enabled the luminescence peak wavelength of the LED to be varied.
The luminescence properties of self-assembled CdS quantum dots ͑QDs͒ were studied. CdS QD structures formed on ZnSe buffer layers without capping layers showed intense photoluminescence ͑PL͒. The PL peak position could be controlled by changing the amount of CdS deposited. Introduction of the capping layer enhanced the PL intensity. The buffer layer material selected also affected the luminescence properties of the CdS QDs, and brighter PL with the higher transition energy was observed by replacing the ZnSe buffer layer with ZnSSe. A light emitting diode structure based on CdS QDs sandwiched in the pn junction of ZnSe was fabricated and bright blue or green luminescence from current injection was observed at 77 K as well as at room temperature.
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