Transmission electron microscopy analysis of the shape and size of semiconductor quantum dots

Strong-beam diffraction contrast in transmission electron microscopy (TEM) associated with quantum dots (coherently strained islands) of InAs deposited on a GaAs substrate is analysed. The elastic displacement field associated with each quantum dot is determined using the finite-element method and the dynamical diffraction theory is subsequently used to simulate the corresponding TEM image contrast. The excellent match observed between simulated and experimental two-beam dynamical images shows that the shape of quantum dots can be readily determined by a geometrical analysis of these images and that the size of the dots can also be obtained under somewhat more restrictive conditions.