Low dislocation density AlGaN epilayers by epitaxial overgrowth of patterned templates
Low dislocation density AlGaN epilayers by epitaxial overgrowth of patterned templates
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DOI：
10.1016/j.jcrysgro.2013.11.052
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发表时间：
2014-02-15
影响因子：
1.8
通讯作者：
Clark, B. G.
中科院分区：
文献类型：
--
作者：
Allerman, A. A.;Crawford, M. H.;Clark, B. G.
我们提出了一种外延生长过程中减少线程位错在整个组成范围内的AlxGa 1-xN。该工艺避免了使用吸收UV的GaN层，并导致空间上均匀的缺陷减少，这消除了将器件精确对准晶片的低缺陷区域的需要。使用所描述的过生长工艺，我们展示了位错密度分别为2 × 10（8）cm（-2）和5 × 10（8）cm（-2）的Al0.3Ga0.7N和Al0.6Ga0.4N外延层，使它们适合作为深紫外底部发射LED和激光二极管的模板。该工艺包括将高度小于1 μ m的亚微米宽的条带图案化到AlGaN/AlN/蓝宝石模板中，随后再生长5-10 μ m厚的AlGaN外延层。梅萨的亚微米宽度允许将继续垂直穿过更宽台面的穿透位错的弯曲。利用1.3毫米厚的蓝宝石衬底（比通常使用的厚3倍），消除了再生长引起的外延层破裂，并且将2英寸直径衬底上的晶片弯曲减小到小于15 μ m。我们观察到从GaN-AlGaN多量子阱结构在340 μ m处发射的光致发光强度增加了7倍，并且当在图案化的Al0.3Ga0.7N模板上生长时从激光二极管异质结构的电致发光增加了15倍。(C)2013年由Elsevier B. V.出版
We present an epitaxial overgrowth process for reducing threading dislocations in AlxGa1-xN over the entire compositional range. This process avoids the use of UV-absorbing GaN layers and results in a spatially uniform defect reduction which eliminates the need for precise alignment of devices to low-defect areas of the wafer. Using the described overgrowth process, we demonstrate Al0.3Ga0.7N and Al0.6Ga0.4N epilayers with a dislocation density of 2 x 10(8) cm(-2) and 5 x 10(8) cm(-2) respectively, rendering them suitable as templates for deep-UV bottom-emitting LEDs and laser diodes. The process involves patterning of submicron-wide-stripes, less than 1 mu m in height, into an AlGaN/AIN/sapphire template and subsequent regrowth of a 5-10 mu m thick AlGaN epilayer. The sub-micron width of the mesa allows for bending of threading dislocations that would continue to thread vertically through wider mesas. Utilizing 1.3 mm-thick sapphire substrates (3 x thicker than commonly used), epilayer cracking from regrowth is eliminated and wafer bow over a 2-in diameter substrate is reduced to less than 15 mu m. We observed a 7 x increase in photoluminescence intensity from GaN-AlGaN multi-quantum well structures emitting at 340 am and a 15 x increase in electroluminescence from laser diode heterostructures when grown on patterned Al0.3Ga0.7N templates. (C) 2013 Published by Elsevier B.V.