氮化蓝宝石衬底上GaN薄膜的微结构与光学性质  

Microstructural and Optical Properties of GaN Films on Nitrided Sapphire Substrates

作　　者：陈志忠[1] 秦志新[2,3] 沈波[4,5] 朱建民[4,5] 郑有炓[4,5] 张国义 

机构地区：[1]北京大学物理系介观物理与人工微结构国家重点实验室,北京100871 [2]北京大学物理系 [3]介观物理与人工微结构国家重点实验室,北京100871 [4]南京大学物理系 [5]固体微结构国家重点实验室,江苏南京210093

出　　处：《发光学报》2002年第2期124-128,共5页Chinese Journal of Luminescence

基　　金：国家自然科学基金资助项目 ( 6 9876 0 0 2 )

摘　　要：用透射电子显微镜 (TEM) ,X射线衍射(XRD)和光荧光谱 (PL)等测量手段研究了GaN薄膜的微结构和光学性质。样品是用光辐射加热MOCVD在蓝宝石衬底上制备的。随着衬底氮化时间的增加 ,扩展缺陷的密度显著增加。在位错密度增加一个数量级时 ,XRD摇摆曲线半宽度 (FWHM)由 1 1″增加到 1 5″,PL谱的黄光发射从几乎可忽略增加到带边发射强度的 1 0 0倍。结合生长条件 。The group-Ⅲ nitrides and their related ternary alloys have been becoming the most attractive material for light emitting diodes (LEDs) and laser diodes (LDs) in the UV and blue spectral range. However, the origins of the yellow luminescence (YL), which is commonly observed in almost undoped and n-type GaN, remain unclear. The nature and the role of initial nitridation of sapphire surface and the generation of threading dislocation (TD) are ambiguous too. It is a possible way to resolve the above problems by studying the microstructures and optical properties combining the growth conditions. In this work, two kinds of GaN films were grown by MOCVD under different initial nitridation time (180 seconds for Sample A, and 90s for Sample B). The growth temperature is about 950℃. The cross-sectional transmission electron microscope (TEM) is performed near the GaN/sapphire interface. Corresponding the growth processes, there are three zones in the GaN layer: buffer layer, 'faulted' zone and 'sound' zone. There are 'haystack-like' domains in the faulted zone, in which there are high density of extended defects. The thickness of the faulted zone is about 0.4μm. Just above this region, the defects density is reduced sharply, and the quality of the layer is improved, which is identified by electron diffraction (ED) patterns. In comparison, Sample A shows about an order lower density of extended defects than Sample B, their columnar diameter is larger and its ED pattern is sharper, too. The buffer layer of Sample B is more smooth than Sample A. The appropriate rougher morphology of the buffer layer may cause that the structural disorder between the high-temperature (HT) grown island and the buffer layer is accommodated by Frank and Shockley partial dislocations. However, the TD is likely to propagate into the HT GaN from the smooth surface of the buffer layer grown after extensively nitridation of substrate. According to the position and width of X-ray diffraction peaks of (0002) and (0004), the size of crystalline

关 键 词：氮化镓 氮化蓝宝石衬底 GAN薄膜 微结构 光学性质 

分 类 号：O484[理学—固体物理] TN304.23[理学—物理]