Resistivity Profiles in Multicrystalline Silicon Ingots Featuring Gallium Co-doping

Three ingots with different doping concentrations have been produced using Elkem Solar Silicon feedstock. Gallium dopants are added to the compensated Elkem Solar Silicon ingots in order to obtain a more uniform resistivity profile throughout the heights, and to avoid a change from p-type to n-type silicon towards the top of the ingots. In addition a reference ingot based on non-compensated silicon has been cast. The resistivity profiles along the height of these ingots are determined using Eddy current measurements on the sides of center blocks. Corresponding resistivity profiles are then estimated using the concentration of dopants in the melt, the Scheil equation, and the numerical device simulation software PC1Dmod6.2. The implementation of advanced c-Si models accounting for changes in the carrier mobility and incomplete ionization of dopants due to the compensation doping were found to be necessary to correctly explain the observations. Using this approach, it was possible to reproduce the experimentally obtained resistivity profiles using slightly modified values for the segregation coefficients. New effective segregation coefficients for B and Ga are proposed.