1999 Fiscal Year Final Research Report Summary
Theoretical analysis of strain relaxation mechanisms of heteroepitaxial layers
| Project/Area Number |
10650074
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Materials/Mechanics of materials
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| Research Institution | The University of Electro-Communications |
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Principal Investigator |
SHINTANI Kazuhito Faculty of Electro-Communications, The University of Electro-Communications, Assoc. Prof., 電気通信学部, 助教授 (00162793)
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| Co-Investigator(Kenkyū-buntansha) |
新谷 一人 電気通信大学, 電気通信学部, 助教授 (00162793)
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| Project Period (FY) |
1998 – 1999
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| Keywords | heteroepitaxial layers / surface morphology / critical strain / stacking fault / surface step / molecular dynamics simulation / quantum dot / strain relaxation |
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| Research Abstract |
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
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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
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Research Products
(24 results)
