Three-dimensional strain field calculations in coupled InAs/GaAs quantum dots

A detailed calculation of the three-dimensional strain field in and around InAs/GaAs quantum dots is presented. The strain field is calculated by mini mizing the elastic strain energy on a cubic grid. Surface boundary conditio ns are incorporated to enable the strain field at the surface of the cap la yer to be examined in detail. This has important implications for the verti cal and lateral ordering of subsequent layers of dots. Results are presente d for a single dot as well as two and four coupled dots. It is found that t he elastic energy density at the surface of the epilayer above a layer of s eed dots exhibits strong minima directly above the seed dots, facilitating vertical ordering. An intriguing result is that, under certain conditions, satellite minima also occur at interstitial points, raising the possibility that a second layer of dots above the seed layer can have significantly mo re dots than the seed layer because of lateral ordering. (C) 2000 American Institute of Physics. [S0021-8979(00)05421-9].