High mobility semiconductor materials.

The main goal of this project is research on semiconductor materials with high carrier mobility compared to silicon. Such layers enable new and improved electronic applications. The semiconductor material that will be investigated at first is germanium, epitaxially grown on silicon. Such heteroepitaxial growth is complicated because of the large lattice mismatch of 4% between germanium and silicon. This difference in lattice dimensions leads to high dislocation densities, which lower the achievable carrier mobility below that of bulk Ge due to scattering. Acquired insights in crystallization from the amorphous phase, will be applied to achieve smooth layers of high crystal quality. Defect densities will be lowered by gathering a better understanding of crystallization processes. The aim is to obtain thin germanium layers with carrier mobilities that are twice as large as for Si(001). A second part of this research project consists of increasing the carrier mobility futher to four times that of Si(001). The strategy that will be used is alloying of Ge with Sn to obtain GeSn compounds. The maximal achievable carrier mobilities for GeSn layers are not known at this moment. However this material system is predicted to exhibit significant higher mobilities in respect to germanium.

Keywords:Semiconductor, Germanium, Tin, Epitaxy, Crystallization, Carrier mobility, Solid phase epitaxy, Heteroepitaxy

Disciplines:Condensed matter physics and nanophysics