Low temperature epitaxial growth of boron-doped silicon thin films

Low temperature (175°C) plasma-enhanced chemical vapor deposition (PECVD) is investigated as an alternative way to form p-n junctions for solar cells production. Compared to standard diffusion, PECVD deposition below 200°C ensures a lower thermal budget and the formation of a sharper doping profile. In this work, boron-doped epitaxial silicon films were grown by PECVD on (100) n-type Si substrates to form the emitter. We focus on the correlation between hydrogen incorporation and the structural and electrical properties of the boron-doped layers to assess their quality in view of the realization of p-n junctions. Using X-ray diffraction and electrochemical capacitance voltage, we observe that there is a strong correlation between hydrogen release (upon annealing the samples) and the activation of boron dopants in the epitaxial film. Interestingly, annealing at 300°C for 10 minutes is enough to activate boron in the emitter layers.