Dislocation mediated surface morphology of GaN
Dislocation mediated surface morphology of GaN
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DOI：
10.1063/1.370150
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发表时间：
1999-05-01
影响因子：
3.2
通讯作者：
Speck, JS
中科院分区：
文献类型：
--
作者：
Heying, B;Tarsa, EJ;Speck, JS
利用原子力显微镜（AFM）对金属有机化学气相沉积（MOCVD）和分子束外延（MBE）生长的GaN薄膜表面进行了研究。由于薄膜中的位错密度很高（10（8）cm（-2）），两种技术生长的薄膜的典型表面形貌主要由三种位错介导的表面结构-钉扎台阶、螺旋小丘和表面凹陷所控制。发现这些表面结构的特征取决于生长技术（MOCVD与MBE）和MBE GaN薄膜生长中使用的III族与V族比例。钉扎步骤，由混合字符位错与自由表面的交叉点，被发现在所有的GaN薄膜。在MOCVD GaN上观察到钉扎台阶主要是直的，在MBE GaN上观察到钉扎台阶弯曲成螺旋形小丘。在台阶流动生长条件下，钉扎台阶向外生长并围绕位错生长，形成螺旋生长丘。发现MBE GaN表面上的螺旋小丘的紧密性随着III/V比的增加而增加。在GaN薄膜的表面上也观察到了由于位错附近的高应变能密度引起的表面凹陷。两个特征的凹陷尺寸被发现在所有MOCVD GaN膜，而凹陷只观察到MBE GaN膜生长与低III/V比。这些观察结果用伯顿、卡布雷拉和弗兰克发展的理论来解释。Soc.伦敦，系列A 243，299（1951）]和Frank [Acta Crystallogr. 4，497（1951）]。(C)1999年美国物理学会。[S0021-8979（99）09409-8].
The surfaces of GaN films grown by metalorganic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) were studied using atomic force microscopy (AFM). Due to the high dislocation densities in the films (10(8) cm(-2)), the typical surface morphologies of layers grown by both techniques were dominated by three dislocation mediated surface structures-pinned steps, spiral hillocks, and surface depressions. The characteristics of these surface structures were found to depend on growth technique (MOCVD vs MBE) and the group-III to group-V ratio used in the growth of MBE GaN films. Pinned steps, created by the intersections of mixed character dislocations with the free surface, were found on all GaN films. The pinned steps were observed to be predominantly straight on the MOCVD GaN and curved into spiral hillock formations on the MBE GaN. Spiral growth hillocks form when pinned steps grow outward and around the dislocation under step-flow growth conditions. The tightness of the spiral hillocks on MBE GaN surfaces was found to increases with III/V ratio. Surface depressions, caused by the high strain-energy density near dislocations, were also observed on the surfaces of the GaN films. Two characteristic depression sizes were found on all MOCVD GaN films whereas depressions were observed only on MBE GaN films grown with low III/V ratios. These observations are explained using theories developed by Burton, Cabrera, and Frank [Philos. Trans. R. Soc. London, Ser. A 243, 299 (1951)] and Frank [Acta Crystallogr. 4, 497 (1951)]. (C) 1999 American Institute of Physics. [S0021-8979(99)09409-8].