| Summary: | 碩士 === 國立成功大學 === 光電科學與工程學系 === 100 === N-type Gallium Nitride semiconductors were used as working electrodes to generate hydrogen gas through water splitting under illumination. In this study, we promoted the efficiency of hydrogen generation by process refinements and the use of electrochemical etching.
First, we fabricated three different structures：two periodic micropillars made by ICP and regrowth, and periodic nanopillars. Under small bias, the defects due to processes and the recombination centers of the semipolar-oriented GaN would reduce the photocurrent density. Nevertheless, under large bias, we could obtain the higher photocurrent density because the increased area of different structures could alleviate the current crowding effect.
Furthermore, we used the electrochemical etching method to generate deep holes in the n-type GaN, and discussed how the dendritic holes formed. For the high-doped n-GaN, we could observe the complete layer removal and electropolshing, so we discussed the possible causes of electropolishing. Finally, we changed the different etching depths by controlling the etching time, and measured their photocurrent densities.
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