Oxygen precipitate behavior of nitrogen-doped Czochralski-grown silicon (CZ-Si) crystals is investigated. It is found that nitrogen doping enhances oxygen precipitation after heat treatment. The oxygen precipitate volume density in nitrogen-doped crystals after heat treatment does not change regardless of the heat treatment temperature, while the oxygen precipitate volume density of crystals which are not nitrogen doped decreases as the heat-treatment temperature increases. The characteristics of precipitation behavior in nitrogen-doped CZ-Si crystals are due to the “grown-in” oxygen precipitates, which already exist in an as-grown state with a high volume density. The oxygen precipitation growth of nitrogen-doped crystals is found to be an oxygen diffusion limited process, the same as in the case of the oxygen precipitation growth of crystals which are not nitrogen doped. The formation mechanism of grown-in oxygen precipitates will also be discussed in this article.

The temperature dependence of the electrical resistivity of molten silicon was measured based on the direct-current four-probe method in the temperature range from the melting point (1,415° C) to 1,630° C. The variation of the resistivity in this temperature region was less than 0.7%, which is much smaller than previously reported values. The measured resistivity near the solodification point was about 72×10-6 Ω cm, which is about 8% smaller than previously reported values. The resistivity of molten silicon showed a local minimum in the range from 1,450° C to 1,500° C. The resistivity of molten silicon was calculated based on Ziman's formula. The temperature dependence of the measured resistivity was not reproduced when the structure factor S(Q) calculated by a simple hard-sphere model was substituted into Ziman's formula, but was reproduced by using the experimental data of S(Q) measured by Waseda which shows the first peak of asymmetric shape. This result suggests that the specific melt structure of molten silicon has a significant effect on the resistivity.

First-principles pseudopotential calculations have been performed to investigate an atomistic model of nitrogen diffusion in silicon crystal. The calculated activation energy of the nitrogen diffusion agrees fairly well with the experimental value of a nitrogen pair, at least as far as the processes in which one of the nitrogen atoms moves first and then the other follows are concerned.

The ordinary Hall effect (OHE), which is caused by an external magnetic field, was studied as a mechanism for the generation of spin current. It has been theoretically elucidated that, under an open-circuit condition, the OHE can contribute to spin-current generation when spin-polarized electrons and holes are simultaneously present as mobile carriers. This OHE contribution to spin current generation is caused by the steady-state kinematics of electrons and holes whose transverse velocities have the same direction. Although anomalous Hall effects may contribute to spincurrent generation, the OHE plays a principal role in the generation of spin current when electrons and holes have approximately the same transport characteristics. The experimental aspects of possible materials for the isomorphic electron and hole systems are argued on the basis of the experimental results of the magnetotransport measurement of yttrium dihydride and preliminary results of the magnetization measurement of hydrogenated films of gadolinium. #

No abstract