MOCVD侧向外延GaN的结构特性  

Structural Characterization of Epitaxial Lateral Overgrowth GaN by MOCVD

作　　者：方慧智[1,2] 陆敏[1,2] 陈志忠[1,2] 陆羽[1,2] 胡晓东[1,2] 杨志坚[1,2] 张国义[1,2] 

机构地区：[1]北京大学物理学院 [2]人工微结构和介观物理国家重点实验室宽禁带半导体研究中心,北京100871

出　　处：《发光学报》2005年第6期748-752,共5页Chinese Journal of Luminescence

基　　金：国家自然科学基金(60376005;60276010);国家"863"计划(2001AA313140;2001AA313060)资助项目

摘　　要：侧向外延(ELO)GaN的原子力显微镜(AFM)表面形貌图像表明,ELO-GaN相当平整,而掩膜区中央有线状分布的小丘群,这是由ELO-GaN在掩膜区中央接合时晶向不一致而产生的缺陷造成的。观察ELO-GaN扫描电子显微镜(SEM)截面图,侧向接合处存在着三角空洞,并且侧向接合导致上述小丘群。X射线衍射(XRD)曲线表明,掩膜边界处的GaN晶面有倾斜。拉曼散射谱表明,掩膜区GaN质量相对于窗口区大为提高。ELO-GaN和普通外延GaN的拉曼散射谱比较表明,ELO-GaN中的应力较小,晶体质量较高。As well-known, heteroepitaxial growth on sapphire is mainly employcd to obtain optoelectronic devices because there is no suitable substrate matching with GaN. Therefore, the GaN layer suffers from a stress due to large difference in lattice constants and thermal expansion coefficients between the GaN and sapphire. To improve the quality of devices, the epitaxial lateral overgrowth （ELO） technique is applied to GaN. ELO-GaN on patterned SiO2/GaN/α-Al2O3 substrate is grown by metalorganic chemical vapor deposition （MOCVD）. First, a high quality 3 μm thick layer of GaN is grown by MOCVD. Next, standard deposition and photolithographic techniques are employed to prepare a set of parallel SiO2 stripes oriented along a （1500） GaN crystal direction separated by window areas which expose the underlying GaN. A second deposition of GaN onto this patterned substrate is then initiated. During the initial GaN growth, the SiO2 stripes function as nonwettable surfaces and no GaN deposition occurs on them. However, once the GaN film growth from the window stripes reaches the tops of the SiO2 stripes, epitaxial lateral overgrowth of GaN commences. The GaN thickness of the second step growth is about 10 μm. The results of a systematic study of the ELO-GaN on sapphire are reported. Atomic force microscopy （AFM） images showed that the surface of ELO-GaN is smooth and that there are linear-configuration hillocks in the middle of mask region, which are caused by the misorientation of crystalline when the ELO-GaN coalesce above the masks. The X-ray diffraction （XRD） curve revealed that the tilts in the （1520） direction between GaN in window regions and mask regions are about 1.2°. Raman scattering spectrum revealed that the stress in the mask region is smaller than that in the window region and also the quality of GaN is much higher in the mask region. As a result, the quality of GaN crystalloid is effectively improved by MOCVD using the ELO technique.

关 键 词：侧向外延 金属有机化学气相沉积 氮化镓 原子力显微镜 拉曼散射 

分 类 号：O472.3[理学—半导体物理] O482.31[理学—物理]