| Summary: | 碩士 === 國立臺灣大學 === 電子工程學研究所 === 97 === In the thesis the optical spectra affected by the distribution of the Ge dots within the MOS structure are reported. There are mainly two series of experiments in this thesis. First, the multi-layer Ge dots within the MOS structure are manufactured by E-gun evaporation and high temperature annealing. Second, grating on the Si bulk are manufactured by E-beam lithography and Ge dots are formed on the grating. To analyze the device characteristics, electro-luminescence (EL) measurement and Raman system are used in these experiments.
By analyzing the Raman spectra, the multi-layer amorphous Ge films begin to crystallize at high annealing temperature, and when the annealing temperature reaches 900℃, the full width at half maximum (FWHM) is the minimum, it means the defect density of the device is small. The EL spectra of the device, annealed 900℃, only show the light from Si. In order to find the reasons that the Ge film did not emit light, the devices with Oxide-Ge-Si structure are fabricated. These Oxide-Ge-Si devices emit light at longer wavelength and we believe that the light is emitted by the defects at the interface between Ge and Oxide.
To improve the optical characteristics, the grating structure is introduced to the Ge dots MOS structure. The grating enhances the intensity of Si and Ge Raman spectra. Although the light emitted from Ge is not found in the thesis, the advantages of grating we stated in the thesis are helpful in the research of Ge and Si optical properties in the future.
In the second section, the effect of the grating on the Si bulk and Ge dots is investigated. Grating on the Si bulk are manufactured by E-beam lithography and ICP-RIE. While the pitch becomes smaller, the intensity of the Si Raman spectrum becomes larger. The intensity is enhanced 7 times while the pitch is 400 nm. The enhancement effect of TM mode is better than TE mode. Furthermore, the Raman of the Ge dots on the Si grating is discussed. The enhancement is the largest when the pitch is 800 nm.
The Raman spectra of the Ge dots in the MOS structure are investigated. Although the light emitted from Ge is not found in the thesis, the mechanism which causes the lack of the light from Ge is found. In the second section, the enhancement of the Raman scattering with grating is a forerunner research. Consequently there are lots of researches are going to be done. In the future, we hope to understand the mechanism, and to integrate the semiconductor processes to fabricate the integrated optical detection devices.
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