| Summary: | 碩士 === 國立中山大學 === 電機工程學系研究所 === 91 === In this thesis, ZnSe self-assembled quantum dots (SAQDs) was grown on GaAs substrate by organic-metal vapor phase epitaxy (OMVPE) with Stranski-Krastanow (S-K) growth mode. The contact-mode atomic force microscopy (AFM) and photoluminescence (PL) are used to measure the surface morphology and optical properties of ZnSe SAQDs, respectively.
Experimental data show that the flow rate of H2Se have a significant influence on the relation between the density and the growth temperature of ZnSe SAQDs. At the H2Se flow rate of 25 sccm, the density of ZnSe SAQDs increases up to 3.96×108 cm-2 as the growth temperature increase from 140℃ to 380℃. However, the growth temperature has a negligible effect of the density of ZnSe SAQDs at the flow rate of 30 sccm. At the H2Se flow rate of 40 sccm, the density of ZnSe SAQDs decreases as the growth temperature increases due to the coalescences of SAQDs.
Furthermore, a cap layer of ZnS was deposited on ZnSe SAQDs. Experimental data indicate that the increase of the thickness of ZnS cap layer results in blue-shifted emission due to the ZnSe SAQDs experience more biaxial strain. Besides, the ZnS cap layer provides an additional source of carriers, which thermalize to the ZnSe SAQDs before recombination, resulting in a significantly stronger photoluminescence signal. In AFM images, the density of ZnSe SAQDs decreases as the increase of the thickness of ZnS cap layer. In conclusion, we have successfully grown the high density of ZnSe SAQDs on the GaAs substrate and deposit the ZnS cap layer on it. Based on the technique, the multi-quantum dots will be developed in the future.
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