Numerical Study of Semiconductor Material Growth
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Nanostructured materials have greatly attracted people’s attention in the past ten years, because they become applicable not only in systems of academic interest, but also to systems of practical impact. In particular, semiconductor nanwstructures have a large potential for applications in optoelectronics. On the other hand, computer modeling of nanostructured material has been developed very much, such as density-functiional theory, molecular dynamics, and Monte Carlo method. Every method has its advantage in different applications.
In this work, three-dimensional quantum dots growth is studied by using kinetic Monte Carlo method. Thin film growth mechanism is well studied. Therefore, first of all thin film growth mechanism is reviewed. Then heteroepitaxy is discussed, including the strain energy effect on thin film growth and two-dimension to three-dimension transition. At last three-dimensional growth of quantum dots is illustrated. In this section, strain energy calculated from point eigen-strain instead of point /line force is extended from two-dimension to three-dimension. Furthermore, in three-dimensional growth an energy barrier, called Ehrlich-Schwoeble barrier, which hinders the descent of atoms to lower level is incorporated.
By using the 3D model, 3D InAs/GaAs QD island size and density evolution under different coverage and temperature is investigated. By comparing our simulation results to experimental ones, we found that there is a size limit for growth coverage. Below the limit existing islands can adsorb more new coming adatoms; however, beyond the limit new islands will be formed to adopt new coming adatoms. We also observed that with increasing temperature, the islands size will increase while their density will decrease.
Various methods have been proposed recently for patterning the substrate so that overgrown QD islands with uniform lateral ordering and equal size distribution can be achieved. Such control may be used to tailor the optoelectronic properties during synthesis and subsequently exploit correlation effects among dots. In this work, we present computer simulations for QD island self-organization on pre-patterned substrates where the pattern control is achieved by adjusting the growth interruption time. Furthermore, correlation between the QD island pattern and substrate anisotropy (due to different crystalline orientations) can also be clearly observed.
Document number: akron1258343695
Permalink: http://rave.ohiolink.edu/etdc/view?acc_num=akron1258343695
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