| Summary: | 碩士 === 中正理工學院 === 應用化學研究所 === 88 === The wide band gap semiconductor GaN with a direct band gap at 3.5eV (wurtzite phase) has attracted a lot of attention in recent years. GaN, which emits blue and ultraviolet lights, can be used to make diodes and laser diodes. In this experiment, a GaN device was designed. A photo-enhanced chemical etching technique with He-Cd laser as the light source was developed to enhance the etching. Samples with different doped and undoped treatment, hydrogen and nitrogen treatment, different mobilities, and solutions (KOH) with different concentrations were adopted. As a result, the etching rate of the undoped GaN samples was better than that of the doped GaN. Higher etching rate with hydrogen pretreatment GaN samples could be observed; however, an opposite result was observed with the nitrogen pretreated GaN samples. Besides, there was no significant change in the etching rate of the GaN samples with different mobilities. In order to explain the results of these experiments, an etching model based on the photo-current measurement was used. A reasonable fitting result was achieved.
From the experimental result, the etching rate changes with the concentrations of KOH solutions. This indicates that the largest etching rate around 1.8 Å/sec is found at pH=14.3 with 1.04 W He-Cd laser illumination. In this study, the variation of the etching rate in KOH solutions is discussed systematically with the etching model proposed by Peng et al. (1998).
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