Axial Distribution of Gallium in Silicon Crystals for Photovoltaic Applications

概要

論文の詳細を見る
The lifetime degradation induced by light illumination or carrier injection observed in Czochralski-grown silicon leads to a significant decrease in solar cell efficiency. The reduction in the extent of this effect has a high potential for the improvement of Czochralski-grown silicon solar cells. An approach to the substitution of boron with gallium in p-type Czochralski-grown silicon crystal has been pursued in a recent study. Since a reduced extent of light-induced degradation of minority carrier lifetime was observed, this approach seems to be very promising. The only disadvantage is the low segregation coefficient of gallium in silicon, resulting in a high resistivity variation over the crystal length compared with that in the case of boron doping. We propose a simple codoping (e.g., gallium and bismuth) method for controlling resistivity variation. Numerical simulations have been performed to study the transport phenomena of dopants in conventional and proposed silicon growth processes using the finite-element method and implicit Euler time integration. It has been demonstrated using mathematical models and numerical analysis that the axial distribution of effective gallium concentration can be modified in Czochralski-grown silicon for photovoltaic applications and made relatively uniform by the proposed doping method.
2007-05-15