Atomistic approach to the strain field in finite-sized heterostructures

Abstract

The numerical code AS_LBFG_v2 developed to simulate the atomic elastic relaxation in finite-sized heterostructures is introduced. To minimize the elastic energy the L-BFGS algorithm is utilized. A user-defined initial atomic configuration, without restrictions on the shape of the matrix embedding quantum dot (QD), can be implemented in the code. By enlarging the pyramidal QD heterostructure towards mesoscopic size, the code generates a strain field distribution similar to that obtained by continuum model for weakly polar semiconductors. The strain field obtained for semi-torus, and spherical shape QDs embedded in finite-sized matrices is also presented. The dependence of the strain field on the cap thickness and the distribution of misfit dislocations in the relaxed configuration are simulated by the code. Program summaryProgram titles:AS_LBFG_v2, AS_Calc_v2CPC Library link to program files:https://doi.org/10.17632/53dshkskct.1Code Ocean capsule:https://codeocean.com/capsule/5342364/tree/v1 and https://codeocean.com/capsule/9050452/tree/v1Licensing provisions: MIT licenseProgramming language: FORTRANNature of problem: An initial constraint atomic configuration of a heterostructure is relaxed by imposing Keating's elastic interaction. The strain field and distribution of misfit dislocations are simulated for various quantum dot shapes and heterostructure materials.Solution method: The elastic energy of the heterostructure is minimized by an L-BFGS algorithm. The strain field is calculated by a discrete mathematical expression at each atomic location.