Effect of substrate temperature on the growth and properties of boron-doped microcrystalline silicon films

Highly conductive boron-doped hydrogenated microcrystalline silicon (\mu c-Si:H) films are prepared by very high frequency plasma enhanced chemical vapour deposition (VHF PECVD) at the substrate temperatures T_\rm S) ranging from 90^\circC to 270^\circC. The effects of T_\rm S on the growth and properties of the films are investigated. Results indicate that the growth rate, the electrical (dark conductivity, carrier concentration and Hall mobility) and structural (crystallinity and grain size) properties are all strongly dependent on T_\rm S. As T_\rm S increases, it is observed that 1) the growth rate initially increases and then arrives at a maximum value of 13.3 nm/min at T_\rm S=210^\circC, 2) the crystalline volume fraction (X_\rm c) and the grain size increase initially, then reach their maximum values at T_\rm S=140^\circC, and finally decrease, 3) the dark conductivity (\sigma _\rm d), carrier concentration and Hall mobility have a similar dependence on T_\rm S and arrive at their maximum values at T_\rm S=190^\circC. In addition, it is also observed that at a lower substrate temperature T_\rm S, a higher dopant concentration is required in order to obtain a maximum \sigma _\rm d.