碩士 / 國立成功大學 / 光電科學與工程學系 / 102 / Hydrogen generation through direct photoelectrolysis of water was studied using photoelectronchemical cells made of different facets of free-standing polar GaN system. To build the fundamental understanding at the differences of surface photochemistry afforded by the GaN polar surfaces, we correlated the relationship between the band structure and photoelectrochemical performance on the different polar facets. The photoelectrochemical measurements clearly revealed that the Ga-polar surface had a more negative onset potential relative to the N-polar and semipolar surface due to the much negative flat-band potential. However,the flat-band potential depend on band bending at the semiconductor-liquid junction. We also use two typical layers of AlGaN/GaN heterostructures as working electrode on photoelectronchemical cells. For AlGaN/GaN heterostrucrtures, we use the bulk layer and the gradual changed layer on different facets of free-standing polar GaN system. The photoelectrochemical measurements exhibit the semipolar GaN with gradual changed AlGaN have the highest photocurrent than the other samples at bias zero voltage. Therefore, we simulate the band bending at bias zero voltage. Though the simulation, we think the photogenerated holes on the valence band are more than the others. Because the amount of the holes which spreads to the electrolyte determine the photocurrent on the photoelectronchemical cells. Therefore, the key parameter of the photoelectronchemical cells is the amount of the holes on the valence band by bending the band diagram.
| Identifer | oai:union.ndltd.org:TW/102NCKU5614032 |
| Date | January 2014 |
| Creators | Ping-KuanLin, 林秉寬 |
| Contributors | Wei-Chih Lai, 賴韋志 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 74 |
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