Photoluminescence in microcrystalline silicon films grown from argon diluted silane

The low-energy photoluminescence (PL) of microcrystalline silicon films grown by plasma-enhanced chemical vapor deposition using argon (Ar) diluted silane has been investigated. For the samples with high crystalline volume fraction (Xc) of more than 80%, it is observed that the luminescence peak appears near 1.0 eV, which is much higher than the value of 0.9 eV observed for the samples with a similar Xc grown from hydrogen dilution. Also, the low-energy PL peak shifts to the higher energy with decreasing deposition power, but it is nearly independent of Ar dilution ratio. The low-energy PL band is suggested to basically arise from a superposition of at least three subbands. From the results it is suggested that the PL band centered at 1.0 eV originates from radiative band tail-to-tail transitions in the crystallites.