對於藍光覆晶式發光二極體之光反射式歐姆電極而言，純Ag之藍光反射率最為優秀，但純Ag與p-GaN間附著性差，更會在退火後凝縮(agglomeration)成島嶼狀結構，導致光電性質的劣化。本論文以雙電子槍蒸鍍系統製備p-GaN的光反射式歐姆電極AgTi(4 at%)、AgTi(2 at%)、Ti(2nm)/Ag(150nm)、AgCo(5 at%)、AgCo(2 at%)、Co(2nm)/Ag(150 nm)及AgNi(2 at%)等七組試片，旨在研究不同合金成分的添加以及爐管退火(FA)與快速退火(RTA)兩種退火方式，對於AgTi、AgCo與AgNi合金光反射式歐姆電極光電特性的影響。探討內容包含歐姆電極的光反射率、金屬薄膜片電阻與特徵接觸電阻，以及各性質之熱穩定性，並使用掃描式電子顯微鏡觀察試片表面樣貌，分析不同合金成分的特性差異及抑制退火後Ag薄膜凝聚的效果。結果顯示合金試片中，添加2 at%的Ti、Co或Ni即可有效抑制Ag薄膜的退火凝聚現象，並可得到良好的藍光反射率、金屬薄膜片電阻及特徵接觸電阻，但隨著添加元素成分的增加，將使其藍光反射率下降與特徵接觸電阻上升，其中AgCo(5 at%)在經時效熱穩定性測試中，產生Ag的側向擴散，導致漏電流的形成。綜合考量光反射率、金屬薄膜片電阻、特徵接觸電阻與熱穩定性，AgCo(2 at%)與AgNi(2 at%)合金作為p-GaN覆晶式LED歐姆電極皆有相當優異的表現。AgCo(2 at%)與AgNi(2 at%)合金在石英爐管內，於大氣環境下進行500℃退火10分鐘後，可以於460 nm具有94%與92%的光反射率，金屬薄膜片電阻約為0.5 Ω/□，特徵接觸電阻分別為3.4 × 10-4 Ω-cm2與1.1 × 10-4 Ω-cm2，且各性質皆有良好的熱穩定性。

This thesis study about optoelectric properties and thermal stability of p-GaN reflective ohmic contacts Ti (2nm) / Ag (150nm), AgTi (2 at%), AgTi (4 at%), Co(2nm) / Ag (150nm), AgCo (2 at%), AgCo(5 at%) and AgNi(2 at%) seven specimens which are prepared by due electron guns evaporation.We discuss the effect, including light reflectivity, sheet resistance of the metal thin film, specific contact resistance and thermal stability, on the optoelectric properties of AgTi, AgCo and AgNi alloy reflective ohmic contacts, be influenced by different alloy composition, different annealing methods, including furnace annealing and rapid thermal annealing.The result show annealed AgCo(2 at%) and AgNi(2 at%) could suppress the agglomeration of Ag film. The specific contact resistance was 3.4 × 10-4 and 1.1 × 10-4 Ω-cm2 , reflectance was 94% and 92% at 460 nm, and sheet resistance of metal film was both 0.5 Ω/□ for annealed AgCo(2 at%) and AgNi(2 at%) at 500℃ in air ambient for 10 min. Both AgCo(2 at%) and AgNi(2 at%) reflective ohmic contacts showed good thermal stability.

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