N型氮化鎵之歐姆接觸及其金屬-半導體場效電晶體之製作

Abstract

在本論文中, 我們採用不同的金屬層來做N型氮化鎵歐姆接觸.為了降低接 觸電阻,我們也利用了高摻雜濃度的氮化鎵層.在歐姆接觸研究上,計算出 鈦在氮化鎵上的位障高度約0.067eV,此值和理論值相當接近鉻具有中等大 小的金屬功函數,我們亦嘗試利用鉻來做氮化鎵之歐姆接觸,同時亦比較鉻 和鈦的歐姆表現從實驗結果得知,即使在退火後鈦的表現仍比鉻好.在此論 文中,我們製作了一個簡單的氮化鎵金屬-半導體場效電晶體.此電晶體是 以鉑極,鈦/銀為源極和汲極,此元件的互導約為6.15mS/mm.目前我們正朝 改進通道層的移動率及歐姆接觸電阻的方向來得到較好的元件特性. In this thesis different metal layers are employed to form ohmic contacts to n-type GaN. In order to further lower the contact resistance, a heavily dopedGaN layer is also used.Ti, which has a lower metal work function, is chosen as the ohmic metal. The barrier height of Ti on GaN is calculated to be 0.067eV, which approaches the value 0.07eV predicted by the theory. Also, Cr is employed to contact n-GaN. Cr has a medium value of metal work function. From our results, after annealing Ti/Al contacts still behave better than Cr/Al contacts. Maybe it iseasier to form TiN than to form CrN.In this work, the fabrication of a simple GaN based MESFET is also described.The Schottky contact and ohmic contact metals are Pt and Ti/Ag, respectively. The transconductance of our device is 6.15mS/mm. Now we are trying to improvethe channel mobilities and ohmic contacts to obtain better device performance.