| Summary: | 碩士 === 國立臺灣科技大學 === 電子工程系 === 97 === In recent years, the commercial market for optoelectronic integrated circuits (OEICs) is expanding at rapid rate. It is necessary that a photodetector fabrication technique of high responsivity and high-speed performance is required for scale-down and cost-reduction concerns.
Hence there has been a remarkable advance in both the physics and processing technologies of polycrystalline silicon. Their significant properties, such as the low-cost and the mass-producability of large-area growth on glass substrate, have attracted much attention as a new optoelectronic material.
In this thesis, all the photodiodes and phototransistors are simulated by MEDICI. The single crystalline silicon photodiodes on bulk substrate and photodiode with extended-p- region are discussed first. We find that a lower concentration substrate (around 1014cm-3) has good frequency response, but the integrated process is too difficult. And we find that the bandwidth of extended-p- region photodiode is higher than that with no extended-p- region in the generally-used substrate doping concentration.
Subsequently, we have implemented the thin film single crystalline photodiode with bandwidth of 500 GHz at 1.2V, the polycrystalline silicon photodiode with bandwidth of 2.6 GHz at 1.2V, the single crystalline and polycrystalline homojunction phototransistors. We reduce the total depth or the n- collector region and adjust the area of p+ region, for improving frequency response and photo responsivity. And we find that adjusting the area of p+ region would lead to different results for single crystalline and polycrystalline.
Finally, we also consider heterojunction junction phototransistors that contain SiGe and Si. For a larger mole fraction germanium on silicon substrate, the SiGe bandgap becomes smaller, thus causing larger electron injection efficiency. However, larger electron injection efficiency shows more degradation of the bandwidth.
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