Theoretical analysis of strain relaxation mechanisms of heteroepitaxial layers

异质外延层应变弛豫机制的理论分析

基本信息

批准号：
10650074
负责人：
SHINTANI Kazuhito
金额：
$ 1.34万
依托单位：
The University of Electro-Communications
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

项目摘要

1 The anisotropic linear stability analysis of surface undulations of semiconductor heteroepitaxial layers was performed. Numerical results for SiィイD21-xィエD2GeィイD2xィエD2/Si systems show that the free energy change for the <100> surface undulations is greater than for the <110> undulations, which means surface undulations are likely to be formed in the <100> directions, that the present theory predicts the critical wavelength for the SiィイD20.82ィエD2GeィイD20.18ィエD2/Si system at 444nm which is in good agreement with the experimental value 44Onm, and that the main mechanism of the strain relaxation is the formation of surface undulations at the Ge fraction greater than 0.5 while it is the misfit dislocation generation at the Ge fraction less than 0.5.2 The molecular dynamics simulations were performed for the dislocation generation from the surface of Si thin films. The Stillinger-Weber potential was used. The effects of surface steps and temperature on the change of the atomic structures are … More investigated. The simulation results show that at the temperatures 500K and 1000K, the energy decrease always occurs if the strain of the system exceeds a critical value whether there exists a surface step or not and whether the strain is compressive or tensile, that the energy decrease occurs due to the formation of (111) stacking faults either at an arbitrary point on the surface if there is no step or at the surface step if there is one, and that both the SィイD2AィエD2 and SィイD2BィエD2 steps can become generation points of stacking faults and the critical strain for the former is smaller from 1% to 2% than for the latter.3 The atomistic calculations of the strain profiles within GaAs/InAs/GaAs pyramidal quantum dot structures were performed. The most stable atomic structures were obtained by the conjugate gradient minimization of the system energy expressed in terms of the Stillinger-Weber potential. The results show that there arises tensile strain just above the top of the island, which causes the vertical self-ordering of the stacked dots, that the larger the thickness of the wetting layer, the greater the magnitude of the tensile strain, and that the present results are in good agreement with those obtained by the inclusion theory. Less

1 对半导体异质外延层表面起伏进行各向异性线性稳定性分析 SiD21-xD2GeID2xD2/Si 系统的数值结果表明，<100> 表面起伏的自由能变化大于 <110> 起伏。表面起伏很可能在<100>方向上形成，目前的理论预测SiD20.82D2GeD20.18D2/Si 体系的临界波长为 444nm，与实验值 44Onm 吻合较好，应变弛豫的主要机制是 Ge 分数大于 0.5 时形成表面起伏，而Ge 分数小于 0.5.2 时失配位错的产生对位错的产生进行了分子动力学模拟使用 Stillinger-Weber 势来研究表面台阶和温度对原子结构变化的影响。模拟结果表明，在温度 500K 和 1000K 时，能量总是下降。如果系统的应变超过临界值，无论是否存在表面台阶，也无论应变是压缩应变还是拉伸应变，都会由于在任意点处形成 (111) 堆垛层错而发生能量下降。如果没有台阶，则在表面；如果有台阶，则在表面台阶处，D2A D2 和 D2B 台阶都可以成为堆垛层错的产生点，并且前者的临界应变比3对GaAs/InAs/GaAs金字塔量子点结构内的应变分布进行了原子计算，通过共轭梯度得到了最稳定的原子结构。以斯蒂林格-韦伯势表示的系统能量最小化结果表明，岛顶部上方会出现拉伸应变，这会导致堆叠点的垂直自排序，即岛的厚度越大。润湿层越多，拉伸应变的大小就越大，并且本结果与夹杂物理论得到的结果非常吻合。