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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了各向异性线性稳定性分析。对SiィイD21-xィエD2GeィイD2XィエD2/Si体系的数值结果表明，表面起伏的自由能变化大于起伏，这意味着表面起伏很可能在&lt；100&gt；中形成。理论预测了Si-ィイ-D20.82-ィエ-D2Ge-ィイ-D20.18-ィエ-D2/Si体系的临界波长为444 nm，与实验值440 nm相吻合，应变弛豫的主要机制是在Ge含量大于0.5时形成表面起伏，而在Ge含量小于0.5时是失配位错产生。采用Stillinger-Weber势。表面台阶和温度对原子结构变化的影响是…的更多的调查。模拟结果表明，在500K和1000K温度下，无论是否存在表面台阶，无论应变是压缩的还是拉伸的，只要系统的应变超过某一临界值，就会发生能量下降；能量的下降是由于在表面上的任意点上形成(111)层错，如果没有台阶，或者在表面台阶上形成(111)层错，SィイD2AィエD2和SィイD2BィエD2台阶都可以成为层错的产生点，前者的临界应变比后者小1%~2%。3对GaAs/InAs/GaAs锥体量子点结构的应变分布进行了原子计算。通过对以Stillinger-Weber势表示的系统能量的共轭梯度最小化，得到了最稳定的原子结构。结果表明，在岛的正上方产生拉应变，导致堆积点在垂直方向上自有序化，润湿层厚度越大，拉应变值越大，与夹杂理论的结果吻合较好。较少