We report investigations on the optical properties of type-II CdTe∕CdSe core-shell quantum dots. By varying the core size, we provide an elegant way to verify that the detected emission signal indeed arises from type-II band alignment. The photoluminescence (PL) peak energy increases with a third root of the excitation power. Both of the PL peak energy and linewidth exhibit unique temperature dependence. All these observations can be rationalized by the band bending effect resulting from the spatially separated photoexcited carriers in a type-II band alignment.

No abstract

Articles you may be interested inEffects of matrix layer composition on the structural and optical properties of self-organized InGaN quantum dots Exciton states in wurtzite InGaN strained coupled quantum dots: Effects of piezoelectricity and spontaneous polarization J. Appl. Phys. 97, 083705 (2005); 10.1063/1.1875736Effects of stacking on the structural and optical properties of self-organized GaN/AlN quantum dots InGaN quantum dots ͑QDs͒ deposited on SiN x nanomasks have been investigated by atomic force microscopy, photoluminescence ͑PL͒, and photoluminescence excitation ͑PLE͒ measurements. It was found that the size of QDs can be well controlled by SiN x nanomasks, enabling the manipulation of quantum confinement effect. The PL spectra of InGaN QDs contain several fine structures, and the main peaks can be attributed to families of QDs with different sizes. The emission arising from InGaN QDs and GaN buffer layer can be clearly distinguished based on PLE measurement, which can be used to improve the interpretation in the previous reports. Our study indicates that the quantum confined Stark effect due to piezoelectric field plays a very important role in the optical properties of InGaN QDs, which is very useful for the application of optoelectronic devices.

No abstract

Selective enhancement and suppression of the photoluminescence arising from Si0.5Ge0.5/Si multiple quantum wells by photonic crystals (PCs) have been demonstrated. The formation of the stop band in PCs is designed to be a filter as well as a reflector. It is found that the self-assembled PCs are able to selectively enhance the luminescence of the type-II transitions at the interface between Si and Si0.5Ge0.5/Si layers and suppress the emission from Si. Our working principle shown here can be extended to many other material systems and should be very useful for creating high power solid-state emitters.