| Summary: | 碩士 === 國立中興大學 === 光電工程研究所 === 104 === The epitaxy InGaAs quantum dot of molecular beam epitaxy on the Bragg reflector is utilized for measuring Raman Spectroscopy and analyzing the relative signal strength and wave number position(GaAs :To mode and Lo mode、InGaAs QDs).
First, InGaAs quantum dots present the characteristic of tunable band gap that the contents of In and Ga are changed for growing the stack layer with different band gap so as to measure the Raman spectra of In and Ga under distinct proportion. As a single-layer quantum dot shows small signal strength, we try surface-enhanced Raman scattering (SERS)to coat a thin layer of Au (about 10nm) on the sample, with thermal evaporator, for annealing. Gold nanoparticles would be self-assembly method to reinforce the signal strength, or gold nanoparticles are directly spin coated on the sample. The result reveals slightly different measurement results of InGaAs under different dimension.
Finally, the Raman spectra of the coupled cavity sample are measured. The top and the bottom are connected with a Bragg reflector and two pairs of quantum dots and a set of Bragg reflector is inserted in the middle. The transmission shows that the transmission peak coupled with 13.5 pairs of DBR and 23.5 pairs of DBR is too close to separate two transmission peak, while inserting 6.5 pairs could improve such a problem. Furthermore, micro-photoluminescence and Raman spectra are used for cross-analyzing the quantum dot Raman spectra effect as the region. It is measured that the quantum dot under vertical coupling appears larger Raman signals than the single-layer quantum dot. Besides, the Raman spectra reveal that the back-end process would damage the sample structure because of high temperature. It is expected to introduce Raman spectra as the rough estimated coupled cavity sample structrure.
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