A doped silicon layer is formed in a batch process chamber at low temperatures. The silicon precursor for the silicon layer formation is a polysilane, such as trisilane, and the dopant precursor is an n-type dopant, such as phosphine. The silicon precursor can be flowed into the process chamber with the flow of the dopant precursor or separately from the flow of the dopant precursor. Surprisingly, deposition rate is independent of dopant precursor flow, while dopant incorporation linearly increases with the dopant precursor flow.