Adequate Method for Decoupling Bulk Lifetime and Surface Recombination Velocity in Silicon Wafers

Abstract

In this paper, we present an appropriate method of decoupling surface and bulk recombination processes in silicon wafers. The study was carried out using the surface passivation of multicrystalline silicon wafers by ethanolic solution of iodine at different molarities varying between 0.01 M and 0.1 M. The effect of the concentration of ethanolic iodine solution on surface passivation effectiveness was investigated by using quasi steady state photoconductance technique. Reproducible experiments have shown that the best passivation is reached for a molarity of around 0.02 M. The carrier lifetime after passivation at 0.02 M has been improved by more than one order of magnitude, compared to that of the same wafer before the passivation. Using an adequate modeling of minority carrier lifetime curves τ (∆n), based on Hornbeck-Haynes model, surface recombination velocity was calculated.The minimum values of surface recombination velocity have been found to be approximately 120 cm/s for 0.02 M. The modeling results indicate that the minority carrier lifetime improvement can be easily correlated with the decrease of the surface recombination velocity for a fixed bulk lifetime τ b = 115 µs.

Investigation of Degradation of Electrical Properties after Thermal Oxidation of p-Type Cz-Silicon Wafers

“…Then, in order to minimize surface recombination, the wafers were passivated with iodine-ethanol. This technique provides very low surface recombination velocities and hence we can assumed that τ eff ≈ τ bulk [14].…”