臺灣博碩士論文加值系統

氮化鎵(GaN)材料有很好的光電特性，已廣泛的應用於發光元件如藍、綠光發光二極體；有鑑於氮化鎵的寬能隙特性，是非常適合製作高功率電子元件的材料，如場效電晶體(FET)和双極性異質接面電晶體(HBT)。
要製作特性優良的場效電晶體，首要條件是閘極的漏電流要小。矽(Si)材料有品質很不錯的氧化物－二氧化矽(SiO2)，所以金氧半場效電晶體(MOSFET)已廣泛的被採用；而砷化鎵(GaAs)材料由於沒有適合的氧化物，因此在閘極改採蕭特基接觸(Schottky contact)，雖然如此仍可獲得不錯的元件特性。
本研究是利用氮化鎵材料來製作金半場效電晶體(MESFET)。以鈦/鋁(Ti/Al) 金屬作為汲極與源極的歐姆接觸(ohmic contact)電極，鎳(Ni)金屬和氮化鎵形成蕭特基接觸(Schottky contact)作為閘極的電極。文中將對氮化鎵金半場效電晶體的製作、量測與元件的I-V特性做詳細的說明與討論 。

As GaN material shows very good optoelectronic properties, it has been widely used in the application of light emitting devices, such as blue and green light emitter diodes (LED). Also, GaN with large energy bandgap is very suitable for the fabrication of the high power electronic devices, such as FETs and HBTs.
The most important requirement for the fabrication of high quality FETs is that the gate leakage current should be as low as possible. Based on the conventional experience, the gate structure might be MOS, MIS, or Schottky contact.
In this work, the GaN layer structures for the fabrication of MESFETs were grown on sapphire substrates by metal-organic chemical vapor deposition (MOCVD). We adopted an alloy of Ti/Al for the formation of ohmic contact on both drain and source terminals. An alloy of Ni was used for the Schottky contact on the gate terminal. Finally, the processed FET devices were measured and the characteristics of I-V curves would be analyzed and discussed.

第一章　序論
1.1 研究動機．．．．．．．．．．．．．．．．．．1
1.2 氮化鎵特性．．．．．．．．．．．．．．．．．2
1.3 論文架構．．．．．．．．．．．．．．．．．．4
第二章 金半場效電晶體理論基礎．．．．．．．．．．．．．5
2.1 環型傳輸線模型．．．．．．．．．．．．．．．5
2.2 蕭特基接面．．．．．．．．．．．．．．．．8
2.3 接面場效電晶體觀念．．．．．．．．．．．．12
第三章 元件製作．．．．．．．．．．．．．．．．．．．．14
3.1 元件隔離(mesa isolation)製作．．．．．．．16
3.2 歐姆接觸(ohmic contact)電極製作．．．．．．19
3.3 閘極製作．．．．．．．．．．．．．．．．．21

第四章 元件電性量測結果與討論．．．．．．．．．．．．．23
4.1 霍爾量測．．．．．．．．．．．．．．．．．．23
4.2 歐姆量測．．．．．．．．．．．．．．．．．24
4.3 蕭特基接觸量測．．．．．．．．．．．．．．．25
4.4 電性量測．．．．．．．．．．．．．．．．．．28
第五章 結論．．．．．．．．．．．．．．．．．．．．．．31
附錄一．．．．．．．．．．．．．．．．．．．．．．．．．32
參考文獻．．．．．．．．．．．．．．．．．．．．．．．．34

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