Precise measurement of diffusion coefficient in semiconductor melt under strong magnetic field

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In the present study, diffusion coefficients in semiconductor melt were measured precisely by utilization of a strong static magnetic field from the melting point of the specimen to 1500 K and then the measured data were compared with those obtained in the microgravity environment and with the estimated values by a hard sphere model.Some experimental conditions for diffusion experiment in a static magnetic field were derived by a numerical simulation based of a fine element method. Based on the numerical result, the diffusion experiments for In-Sn, Ga-doped Ge, Ge-Si and In_*Ga_<1*>As melts were performed using an image furnace in a static magnetic field. The obtained results for the inter-diffusion coefficients were as follows.1. InSn : The obtained coefficients near the melting point agreed well with those estimated by a hard sphere model However, the temperature dependency of the experimental values at high temperature was almost same as the space experiment result. The physical model for diffusion process in a so-called "simple liquid" should be modified based on the experimental data obtained in higher temperature.2. Ga-doped Ge and Ge-Si : The obtained coefficients were much higher than those estimated by the hard sphere model. The results supports validity of the Itami's model which assumes molten Ge has a structure with a weak covalent bonding between the molecules.3. In_*Ga_<1*>As : No reliable data was obtained by the present method due to the segregation of the solute species, because die segregation coefficient was large in the pseude-binary phase diagram. A shear cell method with an application of strong static magnetic field is a promising way to improve reliability of the experimental data in the case of alloy with a large segregation coefficient.