Growth and Characterization of Phosphorus Doped Silicon Nanocrystals Embedded in Silicon Nitride Matrix
| Autor: | Ping-jung Wu, 巫秉融 |
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| Rok vydání: | 2013 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 101 For development of next generation crystalline Si solar cells, one of the new concepts for heterojunction solar cells is using wide bandgap materials as emitter layers due to the higher light transmittance. Silicon nanocrystals (Si-NCs) embedded in a wide bandgap dielectric matrix, such as SiOx, SiNx, and SiCx could be used for this purpose. Moreover, for increasing the conductivity of Si-NCs, incorporating the dopants into Si-NCs has also been demonstrated. So far, the doped Si-NCs in SiOx or SiCx matrix have been used for device fabrication. However, there are few studies for discovering the properties of the doped Si-NCs embedded in SiNx, even if SiNx has a higher bandgap than SiCx and better conductivity than SiOx theoretically. In this dissertation, we first utilized electron cyclotron resonance chemical vapor deposition (ECRCVD) rather than sputtering or inhomogeneous implantation process to grow homogeneous Si-rich SiNx films doped with phosphorus atoms. The initial doping concentration was controlled by changing the introduced [PH3]/[SiH4] gas flow ratio. The as-grown phosphorus doped Si-rich SiNx thin films were then annealed for the formation of phosphorus doped Si-NCs. The effects of phosphorus additives on the Si crystallization behavior in Si-rich SiNx films were investigated. From the experimental results, existence of phosphorus enhances phase separation of Si-rich SiNx and Si crystallization rate. As the phosphorus content within the as-grown Si-rich SiNx thin film increases, the Si-NC size in the Si-NCs/SiNx film increases under the same annealing conditions. In addition, the bonding configurations of phosphorus atoms have been investigated and we could speculate that the phosphorus atoms would probably position at three regions according to the analysis results, including Si-NCs, boundaries between Si-NCs and SiNx, or SiNx matrix. Furthermore, observation of the Fano interference and improvement in conductivity of Si-NCs/SiNx films as a function of the phosphorus content within the as-grown Si-rich SiNx thin film provide evidences for the phosphorus activation, that is, the phosphorus atoms could position at the substitutional sites within Si-NCs. Owing to the achievement of Si-NCs n-type doping, Si-NCs/c-Si heterojunction solar cells have also been realized with a best power conversion efficiency of 8.6%. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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