在本論文中，我們致力於研究液相沉積二氧化鈦薄膜於氮化鎵材料上的特性表現。相較於其他沉積系統，液相沉積法具有低成本以及簡易操作的優點，只要將氮化鎵材料晶片浸入調配好的溶液中即可在低溫環境下(30-60℃)沉積一均勻的薄膜，完全不需要額外的電壓或能量。
在元件應用方面，我們成功利用液相沉積二氧化鈦於氮化鋁鎵/氮化鎵異質接面場效電晶體形成金氧半異質接面場效電晶體。傳統異質接面場效電晶體在最大閘極1 V偏壓下最大汲極電流為334 mA/mm，最大轉導99 mS/mm，逆向崩潰電壓為-49.6 V；金氧半異質接面場效電晶體在最大閘極5 V偏壓下最大汲極電流為760 mA/mm，最大轉導90 mS/mm，逆向崩潰電壓為-147.2 V，此外金氧半結構閘極漏電流可以改善超過5.5萬倍。另外，我們亦藉由比較偏壓應力量測的結果，顯示金氧半結構能藉由降低表面狀態所造成的影響進而抑制電流坍塌現象。

In this study, we demonstrate that TiO2 film can be deposited on GaN material through liquid phase deposition (LPD). The liquid phase deposition system is advantageously cost effective and simple compared to other deposition systems. A uniform film can be deposited on GaN material only through immersion in a solution at a low temperature (from 30-60℃) without any assisted energy source.
Here, the liquid-phase AlGaN/GaN HFETs deposited TiO2 as gate insulators were successfully fabricated. The maximum drain current density for the conventional HFETs was at 334 mA/mm, with a maximum VGS of 1 V. The peak extrinsic transconductance was 99 mS/mm, while the breakdown voltage was -49.6 V. On the other hand, the maximum drain current density for the MOS-HFETs with a TiO2 thickness of 50 nm was 760 mA/mm, with a maximum VGS of 5 V. The peak extrinsic transconductance was 90 mS/mm, and the breakdown voltage was -147.2 V. The gate leakage current density was significantly improved by nearly 55,000 times in the MOS-HFET structure, compared with the conventional HFET. Furthermore, the bias stress measurement showed that the MOS-HFET structure can reduce the effect of the surface state and suppress the current collapse.

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