氮化鎵(Gallium Nitride, GaN)材料半導體已經被廣泛地應用於在高溫和高功率電子儀器和光電子的設備方面。近年來，氮化鎵系列放大器已陸續有相關發表。傳統的GaN MOSFETs其閘極氧化物多為利用蒸鍍或濺鍍的方式製作，然而氧化物易受到上述製程條件影響導致品質不佳。本論文中，我們利用光電化學(photoelectrochemistry, PEC)，直接成長氧化鋁鎵 於氮化鋁鎵上做為氮化鋁鎵/氮化鎵金氧半異質結構場效電晶體的絕緣層，作為閘極的氧化層，如此可以避免氮化鋁鎵表面的污染並降低氧半接面的界面態。
與相同結構的氮化鋁鎵/氮化鎵金半異質結構場效電晶體比較:我們可以降低閘極漏電流達一萬倍以上。，漏電流大約在10-9A，這與金半異質結構場效電晶體的漏電流10-5A 有很顯著的提升。而在汲極飽和電流方面，閘極的氧化層40nm的氧化鋁鎵，可以發現到，在閘極電壓為0V 時，其ID分別為580mA/mm、536 mA/mm，而其ID最大值又分別為678mA/mm、624mA/mm。我們也發現到金氧半異質結構場效電晶體的閘極擺幅電壓(GVS)為9V，而金半異質結構場效電晶體則為5.5V。在高頻增益我們也能夠發現特性上的提升，元件偏壓在VGS=-4V、VDS=10V的高頻增益，其電流截止頻率為5.6GHz，功率增益截止頻率為10.6GHz。可以與MES-HFET(fT =2.8GHz，fMAX =7.2GHz)比較有顯著的提升。

Gallium nitride based semiconductors have been extensively used in high-temperature and high-power electronic devices and optoelectronic devices. With regard to the GaN amplifiers have been reported[1]. In conventional GaN MOSFETs, the gate oxide is externally deposited, such as SiO2, MgO, and Cd2O3. However, the quality of gate oxide is affected by the contaminant of the GaN surface. It causes the degradation of the devices to have larger gate leakage current and reduce the breakdown electric field. In this study, we use the photoelectrochemical (PEC) oxidation method to directly grow oxide films on AlGaN surface as gate dielectric layer of our AlGaN/GaN MOS-HFETs. It can avoid the influence of the contaminant of the AlGaN surface and improve the quality of the interface between AlGaN and gate oxide.

Compare AlGaN/GaN MES-HFETs with MOS-HFETs, the gate leakage current can be reduced more than four orders of magnitude even at room temperature, the leakage current at room temperature was about 10-9A, which is apparently better than MES-HFETs(10-5 A). The saturation drain current at VG=0V of MOS-HFETs and HFETs is 580mA/mm and 536mA/mm, respectively. The maximum value of the drain-source current of MOS-HFETs and HFETs is 678mA/mm and 624mA/mm, respectively. It was found that gate voltage swing (GVS) was 9V for MOS-HEMTs and 5.5V for MES-HFETs, respectively. In high frequency performance, the fT for MOS-HFETs and MES-HFETs was 5.6 GHz and 2.8 GHz, respectively. Moreover, the corresponding fmax for MOS-HFETs and MES-HFETs were 10.6 GHz and 7.2 GHz, respectively. Such results indicated that MOS-HFETs have better electric performances for high frequency applications.

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