Effect of Steady Bias Light on Carrier Lifetime in Silicon Wafers with Chemically Passivated Surfaces

Abstract

We found that even a silicon surface chemically passivated with ethanol-iodine solution represents an active state in the recombination process of excess carriers. Hence, the decay of excess carriers is not a simple exponential decay and the time constant of decay depends strongly on the injection level of excess carriers. This injection-dependent nonexponential decay can be eliminated by illumination with a weak steady bias light. In other words, we recommend the use of a bias light illumination for measurements of bulk carrier lifetime with the technique of chemical passivation, since the illumination results in a low surface recombination velocity of below 5.5 cm/s in a wide range of injection level of 1–200%.