A silicon wafer for a solar cell is doped with phosphorus at during growth
PHYSICS · Subjective · Fermi University Physics · Condensed Matter, Materials & Soft Matter · Crystal structure, bonding and diffraction · Semiconductor physics and devices
Condensed Matter Physics, Ch Real crystals: vacancies, dislocations and the strength of metals
Problem
A silicon wafer for a solar cell is doped with phosphorus at Nd=1×1016cm−3 during growth. Later testing finds it contaminated with iron at NFe=3×1011cm−3, more than thirty thousand times less concentrated than the phosphorus. Explain, using where each impurity places its level in the gap and the recombination process of Section 13.7, why the phosphorus does not shorten the minority-carrier lifetime while the iron, at a far lower concentration, can make the wafer unfit for a solar cell. State plainly what actually determines whether an impurity behaves this way.