Elastic Strain Distribution in GaN/AlN Quantum Dot Structures: Theory and Experiment

Summary

We present a theory of strain distribution in GaN/AlN quantum dot (QD) structures and compare the results of calculations with experimentally measured strain maps from HRTEM images using geometrical phase analysis. We find that the AlN spacers situated between the wetting layers are almost fully relaxed. On the contrary, the AlN spacers located between the vertically correlated GaN QDs are found to be in a tensile strain state. This result demonstrates that the biaxial strain approximation is not valid for the case of a three-dimensional system like a QD.