斜切蓝宝石衬底上GaN薄膜的位错降低机制  

Dislocation reduction mechanism os GaN films on vicinal sapphire substrates

作　　者：徐爽 许晟瑞 王心颢 卢灏 刘旭 贠博祥 张雅超 张涛 张进成[1] 郝跃[1] Xu Shuang;Xu Sheng-Rui;Wang Xin-Hao;Lu Hao;Liu Xu;Yun Bo-Xiang;Zhang Ya-Chao;Zhang Tao;Zhang Jin-Cheng;Hao Yue(Key Laboratory of the Ministry of Education for Wide Band-Gap Semiconductor Materials and Devices,National Engineering Research Center of Wide Band-gap Semiconductor,School of Microelectronics,Xidian University,Xi’an 710071,China)

机构地区：[1]西安电子科技大学微电子学院,宽禁带半导体国家工程研究中心,宽禁带半导体材料与器件教育部重点实验室,西安710071

出　　处：《物理学报》2023年第19期188-194,共7页Acta Physica Sinica

基　　金：国家重点研发计划(批准号:2022YFB3604400);国家自然科学基金(批准号:62074120,62134006);中央高校基本科研业务费(批准号:JB211108)资助的课题。

摘　　要：GaN材料以其宽禁带、高击穿电场、高热导率、直接带隙等优势被广泛应用于光电子器件、大功率器件以及高频微波器件等方面.由于GaN材料异质外延带来的大晶格失配和热失配问题,GaN在生长过程中会产生大量位错,降低了GaN材料晶体质量,导致器件性能难以进一步提升.为此,研究人员提出使用斜切衬底来降低位错密度,但是关于斜切衬底上外延层的位错湮灭机制的研究还不充分.所以,本文采用金属有机化合物化学气相淀积技术在不同角度的斜切蓝宝石衬底上生长了GaN薄膜,采用原子力显微镜、高分辨X射线衍射仪、光致发光测试、透射电子显微镜详细地分析了斜切衬底对GaN材料的影响.斜切衬底可以显著降低GaN材料的位错密度,但会导致其表面形貌发生退化.并且衬底斜切角度越大,样品的位错密度越低.通过透射电子显微镜观察到了斜切衬底上特殊的位错终止现象,这是斜切衬底降低位错密度的主要原因之一.基于上述现象,提出了斜切衬底上GaN生长模型,解释了斜切衬底提高GaN晶体质量的原因.GaN materials are widely used in optoelectronic devices,high-power devices and high-frequency microwave devices because of their excellent characteristics,such as wide frequency band,high breakdown electric field,high thermal conductivity,and direct band gap.Owing to the large lattice mismatch and thermal mismatch brought by the heterogeneous epitaxy of GaN material,the GaN epitaxial layer will produce a great many dislocations in the growth process,resulting in the poor crystal quality of GaN material and the difficulty in further improving the device performance.Therefore,researchers have proposed the use of vicinal substrate to reduce the dislocation density of GaN material,but the dislocation annihilation mechanism in GaN film on vicinal substrate has not been sufficiently studied.Therefore,in this paper,GaN thin films are grown on vicinal sapphire substrates at different angles by using metal organic chemical vapor deposition technique.Atomic force microscope,high resolution X-ray diffractometer,photoluminescence testing,and transmission electron microscopy are used to analyze in detail the effects of vicinal substrates on GaN materials.The use of vicinal substrates can significantly reduce the dislocation density of GaN materials,but lead to degradation of their surface morphology morphologies.And the larger the substrate vicinal angle,the lower the dislocation density of the sample is.The dislocation density of the sample with a 5ºbevel cut on the substrate is reduced by about one-third compared to that of the sample with a flat substrate.The special dislocation termination on the mitered substrate is observed by transmission electron microscopy,which is one of the main reasons for the reducing the dislocation density on the mitered substrate.The step merging on the vicinal sapphire substrate surface leads to both transverse growth and longitudinal growth of GaN in the growth process.The transverse growth region blocks the dislocations,resulting in an abrupt interruption of the dislocations during propaga

关 键 词：斜切蓝宝石衬底 GAN 位错终止 透射电子显微镜 

分 类 号：TQ133.51[化学工程—无机化工] TB383.2[一般工业技术—材料科学与工程]