Quantitative Auger electron spectroscopic analysis of Ge surface segregation in Si/Ge/Si(100) heterostructures

Germanium surface segregation in Si/Ge/Si(100) heteroepitaxial structures has been studied by quantitative Auger electron spectroscopy (AES) and reflection high energy electron diffraction (RHEED). Ge segregation was measured for 1–4 ML Ge, for slow Si growth rates (3×10−4 nm/s) at moderate deposition temperature (520 °C). A layer growth model is used to infer segregation probabilities between 90% and 98%, increasing with Ge layer thickness, especially between 1 and 2 ML. Using this model, the Ge profile in the cap layer is calculated. Surface roughness is just noticeable at 4 ML, and is incorporated into the model in an illustrative manner. A two-state model is used to determine the segregation energy, 0.24±0.02 eV, for 2–3 ML.