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使用气相沉积SiO2和普通光刻以及湿法腐蚀方法,在c面蓝宝石上开出不同尺寸的正方形窗口,在窗口区域中露出衬底,然后使用氢化物气相外延(HVPE)方法选区外延GaN薄膜.采用光学显微镜、原子力显微镜(AFM)、扫描电子显微镜(SEM)、高分辨率双晶X射线衍射(DCXRD)和喇曼谱测试(Ramanshift)对薄膜进行分析.结果表明,在c面蓝宝石衬底上独立的正方形窗口区域中外延生长的,厚度约20μm的GaN薄膜,当窗口面积为100μm×100μm时,GaN表面无裂纹;而当窗口面积为300μm×300μm和500μm×500μm时,GaN表面有裂纹.随着窗口面积的减小,GaN双晶衍射摇摆曲线的(0002)峰的半高宽(FWHM)减小,表明晶体的质量更好,最小的半高宽为530″.从正方形窗口区的角上到边缘再到中心,GaN的面内压应力逐渐减小,分析认为这与GaN横向外延区(ELO区)与SiO2掩膜之间的相互作用,以及窗口区到ELO区的线位错的90°扭转有关.
Using vapor deposition of SiO2 and conventional photolithography and wet etching methods, a square window of different sizes was opened on a c-plane sapphire, a substrate was exposed in the window region, and epitaxial GaN films were then selected using a hydride vapor phase epitaxy (HVPE) method. The films were analyzed by optical microscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM), high-resolution double crystal X-ray diffraction (XRDRD) and Ramanshift.The results show that in the c-plane sapphire substrate GaN film epitaxially grown in an independent square window region and having a thickness of about 20 μm has no cracks on the GaN surface when the window area is 100 μm × 100 μm and cracks on the GaN surface when the window area is 300 μm × 300 μm and 500 μm × 500 μm .With the decrease of the window area, FWHM of the (0002) peak of the rocking curve of GaN bimorph decreases, which indicates that the crystal quality is better and the minimum FWHM is 530. From the square window area Angle to the edge and then to the center, the in-plane compressive stress of GaN gradually decreases. It is considered that the interaction with the GaN lateral epitaxial region (ELO region) and the SiO2 mask and the line position of the window region to the ELO region Wrong 90 ° twist related.