Abstract

The equilibrium distributions of the misfit dislocation density ρ(z) and elastic stresses ε(z) are calculated along the direction of the epitaxial growth of the metamorphic InAlAs/GaAs(001) layer with higher In content (to 87 mol %) and various profiles of varying the composition: step, linear, and root. The calculations are performed using the method based on iteration searching for the minimum total energy of the system. It is shown that the largest differences between various constructions of the buffer layer are observed in the character of distributions ρ(z), rather than ε(z). Unlike the traditional constructions with a step and linear gradients of the composition, which are characterized by a quite homogeneous distribution of misfit dislocations, in a buffer layer with a root composition gradient, the main part of such dislocations is concentrated in the lower part of the layer near the heteroboundary with a GaAs substrate, and their density sharply decreases by more than one order of value along the layer thickness, achieving the value minimum for all abovementioned constructions. In spite of the fact that the important effect of interacting the dislocations to each other is not taken into account in this work, the calculations enable us to establish the main peculiarities of the distributions ρ(z) and ε(z) in various metamorphic buffer InAlAs layers, which were observed experimentally before. Thus, this approach can be effectively used when designing optimal constructions of the device metamorphic heterostructures.

中文翻译：

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不同构造的变质缓冲InAlAs层中错配位错的分布和弹性机械应力

摘要

沿In含量较高（至87 mol％）且变化较大的InAlAs / GaAs（001）变质层的外延生长方向计算失配位错密度ρ（z）和弹性应力ε（z）的平衡分布。组成变化的轮廓：阶跃，线性和根。使用基于迭代搜索系统最小总能量的方法执行计算。结果表明，在缓冲层的各种结构之间，最大的差异在于分布ρ（z）而不是ε（z）。与具有阶跃和线性梯度的成分的传统结构不同（其特征是错配位错的分布非常均匀），在具有根成分梯度的缓冲层中，此类位错的主要部分集中在结构的下部。在具有GaAs衬底的异质边界附近的层中，它们的密度沿层厚度急剧减小了一个数量级以上的值，从而实现了所有上述构造的最小值。尽管在这项工作中没有考虑到位错相互影响的重要影响，但通过计算，我们可以确定分布ρ（z）和ε（z）在各种变质缓冲层InAlAs层中，这在实验之前就已观察到。因此，当设计器件变质异质结构的最佳结构时，可以有效地使用此方法。