氮化鎵(GaN)因不易成長塊材(bulk)，所以目前成長氮化鎵(GaN)的基板(substrate)是以藍寶石(sapphire)為主，此外亦有成長於碳化矽(SiC)的基板上的。因為氮化鎵(GaN)與藍寶石(sapphire)的晶格常數(lattice constant)不匹配，所以會在氮化鎵(GaN)與藍寶石(sapphire)的介面(interface)間產生天然的應力(strain)，造成磊晶片的品質不佳，最後導致元件的壽命衰退。不過這個問題一直到1983年，S.Yoshida等人利用分子束磊晶(Molecular Beam Epitaxy，MBE)法，在藍寶石(sapphire)基板(substrate)先成長一層氮化鋁(AlN)，即我們俗稱的緩衝層(buffer layer)，然後再繼續成長氮化鎵(GaN)，可以得到品質較佳的氮化鎵(GaN)薄膜。
氮化鎵(GaN)其較優的特性分別為擁有較大的能隙(bandgap)、較大的飽和速度(saturation velocity)與峰值速度(peak velocity)、較大的崩潰電壓(breakdown voltage)、較大的熱導(thermal conductivity)、對化學藥品的不活潑性(chemical inertness)、 以及其本身擁有的光電特性

本文是利用有機金屬氣相沉積磊晶方式成長氮化鎵材料的磊晶片，製作金屬-半導體場效電晶體。我們利用了鎳/金雙層金屬作為閘極的蕭基接觸電極，鈦/鋁/鈦/金等多層金屬作為汲極與源極的歐姆接觸電極，比較在汲極與源極使用不同的合金條件下，製作出特性較佳的元件。並且討論元件的可靠性問題，藉由元件在300℃高溫條件下長時間燒烤，對元件之蕭基與歐姆接觸的影響變化，觀察元件特性是否退化。此外元件在不同溫度下操作，所呈現的特性趨勢均加以討論。元件照光與不照光對元件特性的影響。

We investigate the reliability of GaN metal semiconductor field effect transistor. The high quality GaN was grown by metal organic chemical vapor deposition (MOCVD). We used Ni/Au as a schottky gate and Ti/Al/Ti/Au as a drain source of GaN MESFET. It was found that the performance of GaN MESFET was not changed after heated at 300℃ for 120m. No degradation of ohmic contact and schottky contact was occurred. The better reliability of GaN MESFET was demonstrated.

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