Propagation of threading dislocations and effects of Burgers vectors in HVPE-grown GaN bulk crystals on Na-flux-grown GaN substrates
Propagation of threading dislocations and effects of Burgers vectors in HVPE-grown GaN bulk crystals on Na-flux-grown GaN substrates
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DOI：
10.1063/5.0053766
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发表时间：
2021-06-14
影响因子：
3.2
通讯作者：
Sakai, A.
中科院分区：
文献类型：
--
作者：
Hamachi, T.;Tohei, T.;Sakai, A.
研究了氢化物气相外延(HVPE)生长的GaN大块晶体中线状位错(TDS)的传播行为和Burgers矢量的影响，以及在一种商用的HVPE生长的GaN大块晶体中的影响。基于化学腐蚀和透射电子显微镜的分析表明，腐蚀坑的大小与这些TDS的Burgers矢量密切相关。用大角度会聚束电子衍射技术和平面亮场扫描电子显微镜首次观察到唯一Burgers矢量b=1m+1c的TDS的存在。多光子激发光致发光显微镜观察表明，在两种高压外延生长的GaN晶体中，b=1c的TDS呈弯曲状，而b=1a、1a+1c或1m+1c的TDS呈线形。高压外延GaN中b=1a和1a+1c的TDS在Na助熔剂生长的GaN上的倾斜度受大的对称六角丘的影响较大。B=1a的TDS沿山丘面的倾斜方向倾斜，b=1a+1c的TDS与其Burgers矢量中的a分量平行或反平行于a方向倾斜。这些倾向很容易用单个TD的各向同性弹性理论来解释。山丘是围绕成对的平行混合TD产生的，对于这些TD，a分量彼此相反。这一现象归因于Na助熔剂生长的GaN衬底和HVPE生长的层之间界面处的夹杂物。本文还讨论了其他TD的起源，包括具有b=1m+1c的异常TD。
The propagation behavior of threading dislocations (TDs) and the effects of Burgers vectors in hydride vapor phase epitaxy (HVPE) GaN bulk crystals generated on Na-flux-grown GaN and in a commercially available HVPE-grown GaN bulk crystal were investigated. Analyses based on chemical etching and transmission electron microscopy (TEM) revealed a close correlation between the etch pit sizes and the Burgers vector of these TDs. The existence of TDs with the unique Burgers vector b = 1m + 1c was observed for the first time ever using a large-angle convergent-beam electron diffraction technique and plan-view bright-field scanning TEM. Multi-photon excitation photoluminescence microscopy observations showed that TDs with b = 1c had a meandering morphology in contrast to the linear morphology of TDs with b = 1a, 1a + 1c, or 1m + 1c in both types of HVPE-grown GaN crystals. The inclinations of TDs with b = 1a and 1a + 1c in HVPE-grown GaN on Na-flux-grown GaN were greatly affected by large symmetrical hexagonal hillocks. The TDs with b = 1a were inclined in the slope directions of the hillock planes, while those with b = 1a + 1c were inclined in the a directions parallel or antiparallel to the a component in their Burgers vector. These inclinations were readily explained by the isotropic elastic theory of an individual TD. The hillocks were produced around pairs of parallel mixed TDs for which the a components were opposite to one another. This phenomenon was attributed to inclusions at the interface between the Na-flux-grown GaN substrate and the HVPE-grown layer. The origins of other TDs including unusual ones having b = 1m + 1c are also discussed herein.