Direct experimental determination of minority-carrier mobilities and corresponding diffusion coefficients in highly doped p- and n-type silicon have apparently not been performed until now. We have determined the minority-carrier diffusion coefficient in phosphorus- and boron-doped silicon (doping range 1017–1019 cm−3) at 300 K by measuring the complex diffusion length of minority carriers generated by 10.7-MHz optical excitation. Converted into mobilities by the Einstein relation, the results do not differ significantly from Irvin’s majority-carrier mobilities.
Thallium-doped KCl crystals are X-rayed a t 77 OK. They are warmed up to 300 O K and then cooled down again to 77 OK. ESR signals showing a resolved hyperfine structure due to six chlorines are observed. These arise from a TI++ ion on a cation lattice site. The con-
Analytical models have been proposed to describe the onset current density for the initial snapback in the transistor onstate mode and in the blocking state of reverse conducting-insulated gate bipolar transistors (RC-IGBT) for the stripe and cylindrical designs of the anode shorts. In cylindrical case, there are two possible ways in designing the anode shorts and the authors have proposed an analytical model for each of them. The considered RC-IGBTs are vertical with soft punch-through type buffer designs. The analytical model has been evaluated with the aid of 2-D device simulations and measurements. The authors have investigated the initial snapback phenomenon for different voltage class devices at a given technology (anode and buffer profiles) and found out that the snapback voltage increases with the blocking capability but not the snapback current density. The authors have also observed that the initial snapback phenomenon is more pronounced at lower temperatures. From the analytical model as well as simulation and measurement results, the authors have found that for a given voltage class and technology, the p +-anode width is the only remaining design degree of freedom which determines the initial snapback. The adjustment of the on-state losses can then be done with the proportion of the n +-short region.
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