Carbon often appears in Si in concentrations above its solubility. In this article, we propose a comprehensive model that, taking diffusion and clustering into account, is able to reproduce a variety of experimental results. Simulations have been performed by implementing this model in a Monte-Carlo atomistic simulator. The initial path for clustering included in the model is consistent with experimental observations regarding the formation and dissolution of substitutional C-interstitial C pairs (C s-C i). In addition, carbon diffusion profiles at 850 and 900°C in carbon-doping superlattice structures are well reproduced. Finally, under conditions of thermal generation of intrinsic point defects, the weak temperature dependence of the Si interstitial undersaturation and the vacancy supersaturation in carbon-rich regions also agree with experimental measurements.
The photoluminescence from individual InP quantum dots embedded in a matrix of GaInP has been studied. In addition to the ground state emission that consists of several peaks, we observe excited states of the dot. These states are observed either via state filling or with photoluminescence excitation spectroscopy. We observe a fast relaxation to the set of states with lowest energy but no relaxation between these states.
In order to simulate the diffusion kinetics during thermal treatments in SiGe heterostructures, a physically-based atomistic model including chemical and strain effects has been developed and implemented into a nonlattice atomistic kinetic monte carlo (KMC) framework. This model is based on the description of transport capacities of native point defects (interstitials and vacancies) with different charge states in SiGe alloys in the whole composition range. Lattice atom diffusivities have been formulated in terms of point defect transport, taking into account the different probability to move Si and Ge atoms. Strain effects have been assessed for biaxial geometries including strain-induced anisotropic diffusion, as well as charge effects due to strain-induced modifications of the electronic properties. Si-Ge interdiffusion in heterostructures has been analyzed from an atomistic perspective. A limited set of physical parameters have been defined, being consistent with previously reported ab initio calculations and experiments. The model has been implemented into a nonlattice KMC simulator and the relevant implementation details and algorithms are described. In particular, an efficient point defect mediated Si-Ge exchange algorithm for interdiffusion is reported. A representative set of simulated interdiffusion profiles are shown, exhibiting good agreement with experiments.
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