Reducing dislocation density in GaN films using a cone-shaped patterned sapphire substrate
Reducing dislocation density in GaN films using a cone-shaped patterned sapphire substrate
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DOI：
10.1016/j.jcrysgro.2009.07.023
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发表时间：
2009-08-15
影响因子：
1.8
通讯作者：
Park, K. H.
中科院分区：
文献类型：
--
作者：
Shin, Hui-Youn;Kwon, S. K.;Park, K. H.
在平坦蓝宝石衬底上直接生长的GaN膜中的穿透位错（TD）密度通常>10（10）/cm（2），这会显著劣化GaN基LED的性质。本文报道了一种使用各种图案化蓝宝石衬底（PSS）降低GaN层中TD密度的方法。采用金属有机化学气相沉积（MOVCD）方法制备了一种锥形PSS，并将其用于GaN的沉积。在GaN的成核初期、生长中期和生长末期制备了三种不同类型的样品。通过透射电子显微镜（TEM）和使用HRTEM图像的应变映射模拟来分析锥形PSS上产生的TD，其评估残余应变分布。大量的TD的产生和晶格畸变的残余应变仍然高于锥形区域的顶部。然而，在锥形区域的斜坡处没有观察到TD和残余应变。这可能是由于在锥形区域的斜坡处通过横向过生长形成GaN层，导致GaN和蓝宝石之间的晶格失配和不相干性较小。总之，使用锥形PSS可以显著降低GaN层中的TD密度，约为10（7）/cm（2）。(C)2009爱思唯尔有限公司版权所有。
The threading dislocation (TD) density in GaN films grown directly on flat sapphire substrates is typically >10(10)/cm(2), which can deteriorate the properties of GaN-based LEDs significantly. This paper reports an approach to reducing the TD density in a GaN layer using a variety of patterned sapphire substrates (PSS). A cone-shaped PSS produced by metal organic chemical vapor deposition (MOVCD) was used for GaN deposition. Three types of GaN specimens were prepared at the initial nucleation stage, middle growth stage and final growth stage. The TDs generated on the cone-shaped PSS were analyzed by transmission electron microscopy (TEM) and a strain mapping simulation using HRTEM images, which evaluated the residual strain distribution. A large number of TDs were generated and the residual strain by the lattice distortions remained above the top of the cone-shaped regions. However, no TDs and residual strain were observed at the slope of the cone-shaped regions. This might be due to the formation of a GaN layer by lateral overgrowth at the slope of the cone-shaped regions, resulting in less lattice mismatch and incoherency between the GaN and sapphire. In conclusion, the TD density in the GaN layer could be reduced significantly, approximately 10(7)/cm(2), using the cone-shaped PSS. (C) 2009 Elsevier B.V. All rights reserved.