Impact of illumination on the effective diffusivity of hydrogen in n- and p-type crystalline silicon

Abstract

This study investigates the impact of strong illumination on the effective hydrogen diffusivity in moderately- and heavily-doped n- and p-type crystalline silicon. Using a photoluminescence-based method calibrated by secondary ion mass spectrometry, we measure the effective hydrogen diffusivity in silicon wafers under both dark and illuminated conditions at 400 °C. The results show notable increases in the effective diffusivity in heavily-doped n-type and moderately-doped p-type silicon samples under illumination, with both approaching the diffusivity of the moderately-doped n-type sample. In contrast, no significant changes in the effective diffusivity were observed in moderately-doped n-type and heavily-doped p-type silicon under illumination. Simulations of the spatially non-uniform excess carrier profiles generated by the 532-nm laser illumination source, combined with hydrogen charge state modelling, show that the applied illumination can significantly alter the hydrogen charge state fractions in comparison to their thermal equilibrium distributions. Based on the simulation results, we present a qualitative analysis of how the hydrogen charge state may directly modify the energy barrier for hydrogen diffusion, and may also promote or impede the formation of metastable hydrogen complexes, thereby altering the observed effective diffusivity of hydrogen. Show more