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Optimization of metamorphic buffers for MBE growth of high quality AlInSb/InSb quantum structures: Suppression of hillock formation
Journal of Crystal Growth ( IF 1.8 ) Pub Date : 2017-11-01 , DOI: 10.1016/j.jcrysgro.2017.03.043
Y. Shi , D. Gosselink , K. Gharavi , J. Baugh , Z.R. Wasilewski

Abstract The optimization of metamorphic buffers for InSb/AlInSb QWs grown on GaAs (0 0 1) substrates is presented. With increasing surface offcut angle towards [ 1 1 ¯ 0 ] direction, the interaction of spiral growth around threading dislocations (TDs) with the offcut-induced atomic steps leads to a gradual change in the morphology of the AlSb buffer from one dominated by hillocks to that exhibiting near-parallel steps, and finally to a surface with increasing number of localized depressions. With the growth conditions used, the smoothest AlSb surface morphology was obtained for the offcut angles range of 0.8–1.3°. On substrates with 0° offcut, subsequent 3 repeats of Al 0.24 In 0.76 Sb/ Al 0.12 In 0.88 Sb interlayers reduces the TD density of AlSb buffer by a factor of 10, while 70 times reduction in the surface density of TD-related hillocks is observed. The remaining hillocks have rectangular footprint and small facet angles with respect to GaAs (0 0 1) surface: 0.4° towards [ 1 1 ¯ 0 ] direction and 0.7° towards [1 1 0] direction. Their triangular-shaped sidewalls with regularly spaced atomic steps show occasional extra step insertion sites, characteristic of TD outcrops. Many of the observed sidewalls are dislocation free and offer atomically smooth areas of up to 1 μm 2 , already suitable for high-quality InSb growth and subsequent top-down fabrication of InSb nanowires. It is proposed that the sidewalls of the remaining hillocks offer local vicinal surfaces with atomic step density optimal for suppression of TD-induced spiral growth, thus providing the important information on the exact substrate offcut needed to achieve large hillock-free and atomically smooth areas on AlInSb metamorphic buffers.

中文翻译:

用于 MBE 生长高质量 AlInSb/InSb 量子结构的变质缓冲液的优化:抑制小丘形成

摘要 介绍了在 GaAs (0 0 1) 衬底上生长的 InSb/AlInSb QW 的变质缓冲层的优化。随着表面切角向 [ 1 1¯ 0 ] 方向增加,螺旋位错 (TDs) 周围的螺旋生长与切屑诱导的原子台阶的相互作用导致 AlSb 缓冲区的形态逐渐变化,从以小丘为主到呈现出近乎平行的台阶,最终到达具有越来越多局部凹陷的表面。在使用的生长条件下,切角范围为 0.8-1.3° 的 AlSb 表面形态最光滑。在具有 0° 切屑的基板上,随后 3 次重复的 Al 0.24 In 0.76 Sb/Al 0.12 In 0.88 Sb 中间层将 AlSb 缓冲层的 TD 密度降低了 10 倍,同时观察到与 TD 相关的小丘的表面密度降低了 70 倍。其余的小丘具有矩形覆盖区和相对于 GaAs (0 0 1) 表面的小刻面角:朝向 [ 1 1 ¯ 0 ] 方向为 0.4°,朝向 [1 1 0] 方向为 0.7°。它们的三角形侧壁具有规则间隔的原子台阶,偶尔会出现额外的台阶插入位点,这是 TD 露头的特征。许多观察到的侧壁没有位错,并提供高达 1 μm 2 的原子级平滑区域,已经适用于高质量 InSb 生长和随后自上而下的 InSb 纳米线制造。建议剩余小丘的侧壁提供具有最佳原子台阶密度的局部邻近表面,以抑制 TD 诱导的螺旋生长,
更新日期:2017-11-01
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