Atomarer Transport und Defekte in Silizium-Germanium

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We plan to investigate the simultaneous diffusion of self- and dopant atoms in isotopically controlled Si1-xGex heterostructures with x ranging between 0(less than)X(less or equal)1. For the diffusion experiments appropriate SiGe isotope structures will be grown by means of molecular beam epitaxy. Secondary ion mass spectrometry will be performed to measure self- and dopant diffusion profiles after annealing. The formation of microscopic defects such as dislocations and aggregates of point defects, which may occur during the growth of the layer structure or during diffusion annealing, will be investigated by means of transmission electron microskopy. First we will focus on diffusion in relaxed SiGe. Then we will conduct similar diffusion experiments with strained SiGe structures. Detailed numerical analysis of the simultaneous diffusion of self- and dopant atoms in SiGe will provide comprehensive information about the mechanisms of dopant diffusion and the properties of the native point defects involved. In particular, we expect to determine the charge state of the native point defects and their individual contributions to self-diffusion. Altogether the diffusion study will reveal the impact of Ge content and strain on dopant diffusion in SiGe.