标题: 氮化镓基板的开发与同质磊晶研究
Development of GaN Substrates and Homoepitaxy
作者: 陈奎铭
Chen, Kuei-Ming
李威仪
Lee, Wei-I
电子物理系所
关键字: 氮化镓;氮化镓基板;同质磊晶;氢化物气相磊晶;GaN;GaN substrate;homoepitaxy;HVPE
公开日期: 2011
摘要: 目前的氮化物光电元件大多成长于藍宝石基板上,然而这种異质磊晶会伴随许多问题,如晶格常數与热膨胀系數的不匹配、高缺陷密度、应力累积与基板翘曲等。本論文主要研究目的是开发氮化镓基板,并利用氮化镓基板进行同质磊晶,以期解决異质磊晶的缺点。
在开发氮化镓基板的部份,利用氢化物气相磊晶法成长氮化镓厚膜,并使用雷射剥離法制备独立式氮化镓基板。接着,利用氢化物气相磊晶法在独立式氮化
镓基板的正面与背面再成长氮化镓厚膜,以改善晶体品质与增加基板厚度,并改
变基板的翘曲程度。此外,利用干式蚀刻的方式,大幅改善独立式氮化镓基板的
翘曲程度,曲率半径明显从1.5公尺增加到17.8公尺,使后续研磨与磊晶制程良
率与效率提高。
在利用金属有机化学气相沉积法于氮化镓基板进行同质磊晶的部份,首先利
用干式蚀刻与化学机械研磨的方式,消除氮化镓基板因为研磨而产生的损害层,
再利用兩阶段成长法进行未參杂的氮化镓薄膜磊晶。最后在氮化镓基板上成长的
高品质氮化镓薄膜,差排密度大约是7x106 cm-2,X光摇摆曲线的半高宽在(002)
与(102)方向大约是92秒与54杪。
Currently, III-nitride devices are almost grown on sapphire substrates owing to their reliability and cost. However, their performance is limited due to the heteroepitaxy which accompanies various issues, such as lattice mismatch, the difference of thermal expansion coefficients, high dislocation density, biaxial stresses, wafer bow, and so on. The main objectives of this dissertation are the development of GaN substrates and the study of homoepitaxial growth on GaN substrates.
On the part of developing GaN substrates, the GaN thick films were grown by hydride vapor-phase epitaxy (HVPE) and separated from the sapphire substrates utilizing the laser lift-off (LLO) technique. Then, the GaN thick films were regrown on the Ga- or N-faces of freestanding GaN substrates to improve the crystal quality, substrate thickness, and wafer bow. Furthermore, the dry etching method was applied here to significantly reduce the wafer bow of freestanding GaN substrates. The bowing radius of a freestanding GaN substrate can be significantly increased from 1.5 to 17.8 m by ICP etching. It can further improve the fabrication efficiency and yield of the polish and chip processes.
On the part of homoepitaxially growing III-nitride layers on GaN substrates by metal-organic chemical vapor deposition (MOCVD), the GaN substrates were first treated by the methods of dry etching and chemical-mechanical polish (CMP) to diminish the damage layer caused by mechanical polish (MP). And the undoped GaN thin films were homoepitaxially grown on GaN substrates by two-step growth. Overall, low dislocation density of 7×106cm-2; narrow (002) and (102) XRD FWHM of 92 and 54 arcsec can be obtained by homoepitaxially overgrowing GaN thin films on GaN substrates.
URI: http://140.113.39.130/cdrfb3/record/nctu/#GT079621808
http://hdl.handle.net/11536/42483
显示于类别:Thesis