Effective gettering of in-situ phosphorus-doped polysilicon passivating contact prepared using plasma-enhanced chemical-vapor deposition technique

Abstract

In this work, we investigated the gettering of the in-situ phosphorus-doped polysilicon passivating contact that was realized through plasma-enhanced chemical-vapor deposition (PECVD) technology. Interstitial iron (Fei) induced artificially was used as the marker for estimating gettering effectiveness. The factors on gettering effectiveness are studied, including the fabrication procedures and the structures of the polysilicon passivating contact. The research suggests that the heavily phosphorus-doped polysilicon layer serves as the gettering pool for iron atoms. We found that the measures including raising the annealing temperature, extending the annealing time, increasing the thickness and doping concentration of polysilicon, and lowering the SiOx thickness are helping to improve the gettering effectiveness. Moreover, the subsequent hydrogenation promotes the lifetime and implied open-circuit voltage by reducing Shockley-Read-Hall (SRH) recombination. The advantage of the polysilicon passivating contact is the significant effect on the improvement in bulk lifetime, so that the low-quality silicon wafer has the chance to be used for solar cell fabrication with notably improved performance by using the excellent gettering and surface passivation of the polysilicon passivating contact. In summary, this work confirmed that the PECVD-prepared in-situ doped polysilicon passivating contact is an effective process to remove more than 99.99% bulk Fe contamination with an optimal formation procedure, which was essential for the industrial manufacture for silicon solar cells.