在本論文中，吾人研製以氧化鎳作為介電層之氮化鎵/氮化鋁鎵異質結構蕭特基接觸式元件，包含了高電子遷移率電晶體以及蕭特基二極體式氣體感測器。
本研究首先探討具有氧化鎳介電層之氮化鎵/氮化鋁鎵高電子遷移率電晶體之特性。透過射頻磁控濺鍍法沉積，氧化鎳介電層可以降低表面電荷，有效地抑制閘極漏電流，進而提升元件特性。
接著本研究將氧化鎳應用於蕭特基二極體上，製成蕭特基二極體式氫氣感測器，以鈀作為蕭特基接觸金屬來檢測氫氣。研究顯示，具有氧化鎳之氣體感測器有較低的漏電流與良好的感測倍率，亦可在施加逆向偏壓的狀態下維持功能。
本研究再以鉑金屬替換鈀，研製另一種蕭特基氣體感測器並以氨氣作為偵測對象。研究顯示具有鈀/氧化鎳結構之氣體感測器對氨氣有不錯的感測倍率，並能在順偏與逆偏的狀態下感測氣體。

In this dissertation, we investigate several AlGaN/GaN heterostructure Schottky contact-type devices with nickel oxide (NiO) dielectric layer, involving high electron mobility transistors (HEMTs) and Schottky diode gas sensors.
We first fabricate AlGaN/GaN HEMTs with NiO dielectric layer and focus on their properties. The nickel oxide, deposited by radio-frequency (RF) sputtering, can reduce interface charges and suppress gate leakage current to improve device characteristics.
The Schottky diode hydrogen sensor with NiO dielectric is also discussed. We use Palladium as Schottky contact metal to perform hydrogen sensing with Pd/NiO/GaN/AlGaN structure. The results show that gas sensors with NiO have low leakage current and well sensing response. Moreover, the devices can maintain sensing ability while applying reverse-voltage.
We then replace Palladium with Platinum metal and fabricate Pt/NiO/GaN/AlGaN Schottky diode to detect ammonia. We found that the Pt/NiO gas sensor has good sensing ability to NH3, and the device can work at both forward- and reverse-biased state.

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