Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/4253
標題: 濕式蝕刻圖案化藍寶石基板表面處理對氮化鎵磊晶影響之研究
Characterization of GaN Epitaxial Layers on Wet-etched Pattern Sapphire Substrates with Various Surface Treatments
作者: 沈俊丞
Shen, Chun-Cheng
關鍵字: GaN, patterned sapphire substrate
氮化鎵
surface treatment
crystallinity
mobility
圖案化藍寶石基板
表面處理
結晶性
載子遷移率
出版社: 精密工程學系所
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摘要: 本論文將以乾式蝕刻對圖案化的藍寶石基板作表面處理,並探討以此基板所成長之氮化鎵薄膜的品質特性。本實驗採用的蝕刻氣體為四氟化碳,對藍寶石基板的蝕刻速率為180 A/min。當藍寶石基板用於成長氮化鎵薄膜時,由於兩種材料的晶格常數不匹配(晶格常數相差16 %),所成長的氮化鎵薄膜將產生許多缺陷,影響薄膜品質。這樣的結果使得載子輻射複合效率降低與產生大漏電流情況,為改善薄膜品質,論文中利用濕式蝕刻完成圖案化藍寶石基板的製作,再使用感應式耦合電漿蝕刻機台做表面處理,藉由乾式蝕刻對基板表面的粗糙度改變,以降低成長後的氮化鎵薄膜缺陷密度。 文章中分析比較乾式蝕刻做表面處理的前後氮化鎵薄膜性質。以高解析雙晶繞射儀、蝕刻孔洞密度法、光激發光光譜圖、掃描式電子顯微鏡與穿透式電子顯微鏡分析結果顯示,經過表面處理的圖案化藍寶石基板,其氮化鎵磊晶膜在高解析雙晶繞射對稱面(0002)面搖擺曲線半高寬降低17 %,非對稱面(10-12)面搖擺曲線半高寬降低12 %,載子遷移率由146 cm2/v-s增加至219 cm2/v-s,顯示薄膜品質有因此改善。
In this thesis, the characteristics of GaN epilayers grown on the wet-etched pattern sapphire substrates (PSSs) with various dry etching treatments have been investigated. The CF4 was used as the etching gas, achieving an etching rate of 180 A/min for the sapphire substrate. The PSS was treated using an inductively-couple-plasma etching system to modify the PSS surface morphology. It is well known that there exist high density defects in the GaN epilayer due to the large lattice mismatch between GaN and sapphire (~16 %). It will reduce the radiative recombination efficiency and cause large leakage current. Moreover, the treatment effects on the crystallinity and optical properties of GaN epilayers will be discussed. We analyzed the results of GaN epilayer grown on wet-etched PSS with and without surface treatment. The GaN epilayer was measured by double-crystal x-ray diffractometry, etch pit density, photoluminescence, scanning electron microscopy, transmission electron microscopy, and van-der Hall measurement. The full widths at half maximum of both x-ray rocking curves in (0002) and (10-12) faces of the GaN epilayer on treated PSS were decreased by 17% and 12%, respectively as compared with those of the sample on untreated PSS. In addition, the electron mobility was increased by 50 % (from 146 cm2/v-s to 219 cm2/v-s). These results indicate that the improvement in epitaxial quality of GaN can be achieved on the PSS with a suitable post dry-etching treatment.
URI: http://hdl.handle.net/11455/4253
其他識別: U0005-1503201114550000
文章連結: http://www.airitilibrary.com/Publication/alDetailedMesh1?DocID=U0005-1503201114550000
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