p-GaN/AgSn與p-GaN/AgCu反射式歐姆電極光電特性與熱穩定性之研究

Study of Optoelectric Properties and Thermal Stability of p-GaN/AgSn and p-GaN/AgCu Reflective Ohmic Contacts

林威浩(Lin,Wei Hao)

指導教授 ： 黃倉秀

國立清華大學/工學院/材料科學工程學系/碩士(2015年)

https://doi.org/10.6843/NTHU.2015.00218

摘要

本論文研究p-GaN的光反射式歐姆電極，以雙電子槍蒸鍍系統製備Sn(2nm)/Ag(150nm)、AgSn(2 at%)、AgCu(4 at%)和AgCu(8 at%)等四組試片，以熱蒸鍍法製備AgCu(T.E.)，加上以單電子槍蒸鍍合金材料製備AgCu(S.E.)等，共六組試片。探討不同合金成分、爐管退火(FA)與快速退火(RTA)兩種不同退火方式，以及不同薄膜蒸鍍製程，對於AgSn及AgCu合金反射式歐姆電極光電特性的影響，包含反射式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。我們發現Sn(2nm)/Ag即可抑制Ag薄膜的高溫退火凝聚，而且其餘的AgSn及AgCu合金薄膜經爐管退火或快速退火，也無凝縮現象產生，且400℃時效退火1小時後反射率變化甚小，金屬薄膜片電阻與特徵接觸電阻數值亦無顯著變化。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，AgSn(2 at%)和AgCu(4 at%)合金有很優異之表現，以製作p-GaN覆晶式LED電極之應用觀點來看，AgSn(2 at%)合金在石英爐管內，於大氣環境下進行500℃退火5分鐘後，可以得到460nm藍光具有102%的反射率，金屬薄膜片電阻約為0.15 Ω/□，特徵接觸電阻約為1.2 × 10-3 Ω-cm2，時效退火後更低至7 × 10-4 Ω-cm2，具備優良的熱穩定性。而AgCu(4 at%)合金在石英爐管內，於大氣環境下進行500℃退火10分鐘後，可以得到460nm藍光具有102%的光反射率，金屬薄膜片電阻約為0.12 Ω/□，特徵接觸電阻約為8.2 × 10-4 Ω-cm2，時效退火後更低至5.5 × 10-4 Ω-cm2，且熱穩定性佳。兩者都是GaN藍光LED的優良反射式歐姆電極。

關鍵字

反射式歐姆電極 ； 光電特性 ； 熱穩定性

並列摘要

This thesis study about optoelectric properties and thermal stability of p-GaN reflective ohmic contacts Sn (2nm) / Ag (150nm), AgSn (2 at%), AgCu (4 at%) and AgCu (8 at%) four specimens which are prepared by due electron guns evaporation and AgCu (T.E.) prepared by thermal evaporation plus a AgCu(S.E.) prepared by single electron gun evaporation six specimens in total. 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 AgSn and AgCu alloy reflective ohmic contacts, be influence by different alloy composition, different annealing methods, including furnace annealing and rapid thermal annealing, and different deposition process. We found that Sn (2nm) / Ag film can inhibit the aggregation of Ag film at high temperature annealing, and there are no aggregation be found on AgSn and AgCu thin film after furnace annealing and rapid thermal annealing, and after aging at 400 ℃ for one hour, the influence on reflectivity, sheet resistance of the metal thin film and specific contact resistance are very small. Comprehensive consideration above-mentioned properties, AgSn (2 at%) and AgCu (4 at%) alloys thin films are excellent. After anneal 5min in air at 500 ℃, the AgSn(2 at%) reflectors produce low specific contact resistance(1.2 × 10-3 Ω-cm2),and even lower after aging(7 × 10-4 Ω-cm2), high reflectivity(102% at 460nm),good sheet resistance of the metal thin film(0.15 Ω/□), and good thermal stability. After anneal 5min in air at 500 ℃, the AgCu(4 at%) reflectors produce low specific contact resistance(8.2 × 10-4 Ω-cm2),and even lower after aging(5.5 × 10-4 Ω-cm2), high reflectivity(102% at 460nm),good sheet resistance of the metal thin film(0.12 Ω/□), and good thermal stability.

並列關鍵字

Reflective Ohmic Contacts ； Optoelectric ； Thermal Stability ； p-GaN ； AgSn ； AgCu

參考文獻

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