Study On Growth Directions,Strain Relaxation And Energetics Of Self-Assembly Quantum Dots Inas/Gaas

Semiconductor quantum dots is the basis of microelectronic, optoelectronic devices and circuits in the new generation due to its special characteristics of the. It changes the materials’ photoelectric properties fundamentally. Complicated internal strain fields are caused in and around quantum dots in the growth of self-assembly quantum dots. The release of energy in lattice system induces the reconstruction of surface morphology, this increases the possibility of reduced strain, lower energy, and the stabilized system to improve the various performance of the material. Growth of isolated quantum dots and single-layer quantum dots in different directions are simulated and calculated in this paper. After analysis of the relationship between different energy and the distribution of stress and strain, the inherent laws are identified for these two quantum dots systems. It provides a theoretical basis for control ling the ordered growth of quantum dots in laboratory.Firstly, the strain energy, strain relaxation energy, and free energy are calculated in seven commonly growth direction for the self-assembled pyramidal InAs/GaAs quantum dots system, based on the finite element method of anisotropic elasticity theory. The equilibrium shapes of systems are also studied. It was found that the strain relaxation of quantum dots on (211) surface is the largest and the strain relaxation of quantum dots on (100) surface the smallest. The stress and strain of quantum dots become smaller successively on growth surface (211),(311),(111),(337),(331),(110) and (100). The relationship between stress, strain and the angle between growth surface and [001] is a U-shaped curve. The peak value is near (211) surface. On these surfaces, the equilibrium height to width ratio of the quantum dots is ranged from0.5to0.6.Secondly, the energies of single-layer quantum dots system are calculated in different growth directions. The strain energy and strain relaxation energy are almost the same as the that of isolated quantum dots system. The variations of the energies to growth directions are also similar for two systems.Finally, the stress and strain distributions of both quantum dots systems are compared. The results show that the stress and strain of single-layer quantum dots system are slightly smaller in the wetting layer and the distributions are more moderate.