Quantitative 200 dark-field imaging of InGaAs/GaAs layers: measurement of chemical composition and strain effects

Quantitative analysis of TEM 200 dark-field image contrast in In_xGai_1-xAs/GaAs planar layers was carried out to understand the evolution of strain and chemical contrast as a function of In composition. The transmitted intensity profile across the InGaAs/GaAs layers is obtained using finite element calculation of the 3D strain profile in combination with a dynamical contrast simulation. The In intensity curve as a function of concentration follows a parabola. Strain contrast is a monotonous function of the In concentration and can therefore be used to measure it.