在蓝宝石衬底上外延生长gan薄膜的mocvd工艺研究.doc

在蓝宝石衬底上外延生长GaN薄膜的MOCVD工艺研究
摘要
第三代半导体材料GaN由于具有优良性质使其在微电子和
光电子领域有广阔的应用前景,目前制备GaN的方法主要有分子束(MBE)、***化物气相外延(HVPE)、金属有机物化学气相沉积(MOCVD)。本文介绍了MOCVD法在蓝宝石衬底上外延生长GaN材料并利用其无掩模横向外延生长GaN 薄膜与同样生长条件下,在未经腐蚀预处理的蓝宝石衬底上外延的GaN 薄膜进行对比测试[1]。测试分析结果表明,经过腐蚀预处理的GaN 衍射峰的半峰宽及强度、表面平整度、腐蚀坑密度都明显优于未经腐蚀预处理的GaN 薄膜,使原有生长条件下GaN薄膜位错密度下降50%。并且通过Hal l 测试、x 射线双晶衍射结果、室温PL 谱测试[2]成功地制备出GaN单晶薄膜材料, 取得了GaN 材料的初步测试结果。测试研究发现增加缓冲层厚度、多缓冲层结构可以有效地降低位错密度、提高薄膜质量,其中通过中温插入层结构实验获得了质量最好的GaN 外延层[3]。
关键字:GaN MOCVD 蓝宝石衬底预处理缓冲层外延生长
STUDY OF EPITAXIAL LATERAL OVERGROWTH
OF GALLIUM NITRIDE ON SAPPHIRE BY
MOCVD
By
Haiqing Jiang
Supervisor: Dai
ABSTRACT
Gallium-nitride-semiconductor offers good potential value for application in a wide range of optical display, optical recording and illumination due to its excellent quality. At present, molecular beam epitaxity (MBE), Chloride vapor phase epitaxy (HVPE) and anic chemical vapor deposition (MOCVD) are used to prepare GaN. This text introduces overgrowth of Gallium-nitride on sapphire by MOCVD pares the result with that on non-corrode sapphire. The results proved that thinner full-width at half- maximum(FWHM), higher intensity value of X-ray diffraction,
smoother surface and lower density value of the etching pit were received using patterned substrate, which made sure that under the same growth process the density of the dislocations decreased 50%.After that, it also uses Hall Test, X-ray macle diffraction Test, and PL Spectrum Test under room temperature to check the GaN thin-film material. The results showed that multi-buffer-layer structure could decrease the density of the dislocations and improve the quality of the crystal structure. The GaN epilayer with Intermediate-Temperature insert layer had the best results of all the samples.
KEY WORDS: GaN MOCVD surface pretreatment on sapphire substrate cushion epitaxial growth
第一章绪论
GaN 材料的基本特性
现有的GaN 基化合物的制备技术
GaN 现有制备技术对比
第二章 MOCVD 中影响成膜因素
第三章蓝宝石衬底表面预处理
蓝宝石衬底与处理的原因