Degradation and Recovery of n-Type Multi-Crystalline Silicon Under Illuminated and Dark Annealing Conditions at Moderate Temperatures

Abstract

Recently, an n -type multi-crystalline silicon (mc-Si) was observed to be susceptible to degradation under illumination at elevated temperatures with similarities to carrier-induced degradation in p -type mc-Si. In this study, we demonstrate degradation and regeneration of the effective lifetime of non-diffused n -type mc-Si wafers using illuminated and dark annealing conditions at moderate temperatures. Under illuminated annealing conditions, the degradation and regeneration rates of the n -type mc-Si are observed to be slower than those of the p -type mc-Si; however, the opposite trend was observed under dark annealing conditions. The carrier-induced degradation kinetics of the n -type wafers can be described by degradation and regeneration that occur simultaneously, and the activation energies have been identified to be 1.23 ± 0.16 eV for the degradation process and 1.34 ± 0.08 eV for the regeneration. Surprisingly, no degradation was observed in n -type mc-Si under dark annealing above 160 °C. Rather, at these conditions, a two-stage improvement in the lifetime was observed. Although degradation occurs after a subsequent laser treatment, the stable lifetime at the end of the degradation is still slightly higher than its initial value.