Quantification of InxGa1−xP composition modulation by nanometric scale HAADF simulations

Multijunction solar cell efficiency is highly sensitive to structural and chemical variations. These variations can be quantified at nm scale in InGaP/InGaAs/Ge multijunctions using transmission electron microscopy modes, e.g. diffraction contrast (DC-CTEM) and high angle annular dark field (STEM-HAADF). These studies determined the structure and the composition modulation of InGaP layers with sensitivity below 1% of In composition. To quantify the In-related variation, STEM-HAADF profiles are compared to numerically simulated ones. The fit with the experimental contrast shows local variations of 4.25%In for distances below 30 nm.