Transmission electron microscopy of semiconductor quantum dots

We report on plan-view transmission electron microscopy techniques, by whic h the size, the actual shape and the strain of a coherent quantum dot in se miconductor heterostructures can be measured very accurately. The bright-fi eld suppressed-diffraction imaging condition where no strong diffracted bea m is excited in the sample provides reliable size measurement. Using suppre ssed-diffraction imaging condition, the intensity contour in a coherent isl and is related to the height, and thus the detailed shape and the aspect ra tio can be extracted. The strain contrast of a coherent island imaged using an exact two-beam dynamical diffraction condition is useful for strain mea surement and the corresponding features is related to the shape of an islan d. The physical origins and accuracy of interpretation of the image contras t are discussed, using the simulations and experimental examples.