| Summary: | 碩士 === 國立臺灣大學 === 物理研究所 === 97 === Photodiodes and solar cells are both photo-sensitive devices. They are devices that can absorb light power and change it into the electrical signal. High-efficiency photo-sensitive devices can easily generate a large amount of light electron-hole pairs which hardly recombine. Since electroless wet-etched SiNWs have rough surfaces, they offer excellent opportunities for improving the quantum efficiency of a photo-sensitive device since nanostructures can facilitate light absorption and radial collection of photo-generated carriers, thus giving rise to high efficiency.
Our fabrication process is very simple and low cost, which is very useful for practical application. After SiNW growth, a very thin a-Si:H layer was grown on SiNW by PECVD for passivation., and the thin film of ZnO was grown on a-Si:H by sol-gel methods. Then the p-SiNW/a-Si:H/n-ZnO were annealed in a furnace at different temperatures 500 °C for 0.5 hour to improve ZnO crystalline quality. The device provides an excellent alterative for detecting light.
To reduce the effect of SiNWs'' surface defects, one of the possible ways is to insert an additional a-Si:H layer between ZnO and p-Si nanowires. The additional a-Si:H layer passivates the interface defects due to the presence of atom hydrogen during the deposition. The IPCE result points out that the light current of the p-SiNW/a-Si:H/n-ZnO photodiode shows a significant increase compared with that of p-SiNW/n-ZnO photodiode under small reverse voltage. It indicates that the a-Si:H can effectively passivate the interface defects and play an important rule.
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