标题: 以低压有机金属化学气相沉积于矽基板上成长氮化镓磊晶薄膜
Epitaxial Growth of GaN on Si Substrate by Low Pressure Metal-Organic Chemical Vapor Deposition
作者: 林龚梁
Lin, Kung-Liang
张翼
Chang, Edward-Yi
材料科学与工程学系
关键字: 氮化镓;矽基板;磊晶;GaN;Si substrate;epitaxial
公开日期: 2009
摘要: 此论文,主要利用三种不同方法利用低压有机金属化学气相沉积设备,成长氮化物于6寸矽基板上,并对氮化物半导体异质结构磊晶成长于矽基板上做一探讨。
首先第一种方法,藉由 MOCVD方法,以多层氮化铝与结合渐变氮化铝镓层为缓冲层,已可将高品质氮化镓薄膜成功的成长于6寸矽基板上。缓冲层的结构、薄膜品质与厚度为成长高品质不会龟裂之氮化镓层于矽基板上之主要关键。使用不同温度下成长之多层氮化铝并结合渐变氮化铝镓层为缓冲层,藉由此缓冲层的张应力降低与递增的压应力氮化镓层,以获得成长0.5微米厚度无龟裂氮化镓薄膜于6寸矽基板上。
第二种方法,氮化镓成长于多层氮化铝与结合渐变氮化铝镓层为缓冲层,藉由调变氮化铝中之铝成份,由0调变至66%,藉有调变氮化铝镓中的铝成份,藉以用来缓和因氮化镓与矽基板于磊晶成长所产生的应力。以高解析度X光绕射对于氮化镓薄膜进行对称与非对称的ω/2θ分析与倒置晶格图谱分析氮化铝镓中铝成份组成与氮化镓薄膜所导致的应力之间关系。发现适当的设计氮化铝镓层中的铝成份能有效的缓和氮化镓与矽基板成长时所产生的应力,并成功的应用多层氮化铝与结合渐变氮化铝镓层为缓冲层于6寸矽基板上磊晶成长为裂痕之氮化镓薄膜。
最后,第三个方法,以氮化铝为成核缓冲层并结合两步骤不同成长条件长晶,低应力,低差排密度氮化镓成功的成长于圆型图案化矽基板上。拉曼量测显示氮化镓成长于图案化矽基板具有有效降低薄膜内部应力。以PL对氮化镓薄膜进行量测,PL曲线具有往短波长位置偏移(blueshift)可以更明显证明氮化镓成长薄膜张应力被图案化矽基板部份释放。可以相信因晶格不匹配与热膨胀系数差异过大所产生的应力,可藉由多晶面向的氮化铝缓冲层与此边界产生的差排密度,有助于将氮化铝上成长的氮化镓薄膜释放应力,进而获得于图案化矽基板上成长无龟裂之氮化镓薄膜。
In this thesis, the heterostructure growth of GaN on Si substrate by Low-pressure metal-organic chemical vapor deposition (LP-MOCVD) is studied. The investigation focuses on the growth of GaN on 6 “ Si (111) wafer. There different approaches werw including in this study.
In the first approach, high quality GaN film was successfully grown on 150 mm Si (111) substrate by MOCVD method using multilayer AlN combined with the graded AlGaN layer as buffer. The buffer layer structure, film quality and film thickness are critical for the growth of the crack free GaN film on Si (111) substrate. Using multilayer AlN films grown at different temperatures combined with graded Al1-xGaxN film as the buffer, the tensile stress on the buffer layer was reduced and the compressive stress on the GaN film was increased, as a result, high quality 0.5 μm crack-free GaN epitaxial layer was successful grown on 6” Si substrate.
In the second aaproach, the GaN film was grown on Si substrate using multilayer AlN/AlxGa1-xN buffer by low pressure metal organic chemical vapor deposition (MOCVD) method. The AlxGa1-xN films with Al composition varying from 0~ 0.66 was used to accommodate the stress induced between GaN and Si substrate during GaN growth. The correlation of the Al composition in the AlxGa1-xN films with respect to the stress induced in the GaN film grown was studied using high resolution X-ray diffraction including symmetrical and asymmetrical ω/2θ scans and reciprocal space maps. It is found that with proper design of the Al composition in the AlxGa1-xN buffer layer, crack-free GaN film can be successfully grown on 6” Si (111) substrates using multilayer AlN and AlxGa1-xN buffer layers
Finally, in the third approach, low stress, low defect density GaN film was successful grown on circle array patterned Si (111) substrate using AlN as the nucleation buffer followed by two steps growth of the GaN film. Raman measurement shows a reduction of the in plane biaxial stress for the GaN film grown on patterned substrate. The slight blueshift of the band edge PL peaks further provides the evidence that the tensile stress in the GaN film was relaxed in the patterned Si substrate. It’s believed that the grain boundaries of the polycrystalline AlN buffer layer and the dislocations in the GaN film grown helped to relieve the stress induced by the lattice and the thermal coefficient mismatches during growth.
URI: http://140.113.39.130/cdrfb3/record/nctu/#GT079318816
http://hdl.handle.net/11536/40562
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