Abstract
Spectroscopic technique which possesses both temporal and spacial resolution was developed by combining the pico-second pulsed laser system with the optical microscope. By using this technique, the time-resolved photoluminescence (TRPL) with micron spatial resolution was performed for the self-organized CdSe/ZnSe quantum dots (QDs) fabricated on GaAs(1 1 0) crystal surfaces. PL spectra of CdSe/ZnSe with 10 monolayer (ML) deposition thickness were composed of two emission bands peaking at 2.6 and 2.2 eV. These bands could be ascribed to the emissions from CdSe quantum wells (QWs) acting as wetting layers and QDs, respectively. With macroscopic excitation (spot size: 100 μm), temporal behavior of the emission band of QDs was characterized by multi-exponential decay. However, with microscopic excitation (spot size: 5 μm), it was found that both spectrum shapes and PL lifetimes have changed with sweeping the location of focus. Especially, the lifetimes were quite valuable and were well fitted by the single exponential decay. These results suggest that the radiative lifetime differs very much depending on the degree of exciton localization.
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