Hydrogen-induced-intrinsic transport in undoped microcrystalline silicon

초록

It is demonstrated that microcrystalline silicon (mu c-Si:H) of intrinsic character can be produced by post-growth atomic hydrogen treatment. Undoped mu c-Si:H films with a dark-conductivity activation energy (E (a)) of about 0.20 eV were grown by plasma-enhanced chemical vapor deposition, and then subsequently exposed to an atomic hydrogen plasma. The hydrogen treatment is shown to result in a gradual increase in the E (a) with increasing treatment time, followed by saturation at about 0.57 eV, a value observed for truly intrinsic mu c-Si:H films. In the saturated state, the dark conductivity is on the order of 10(-7) S/cm. The dark conductivity prefactor is found to follow the Meyer-Neldel rule. It is proposed that charge transport takes place in amorphous-like tissue surrounding the crystalline grains. The results are attributed to the Fermi level shift due to a change in the gap state distribution.

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