Entirely μc-Si:H p-i-n structures presenting an enhanced sensitivity to the near infrared region and a positive spectral response under forward bias higher than the open circuit voltage are analysed under different external voltage bias and illumination conditions.
A two phase model to explain the transport properties is proposed using as input parameters the measured experimental data. The results suggest that the transport is preferentially concentrated inside the crystalline grains. The conduction within the amorphous regions is poor. The percolation path is different for electrons and holes and is determined by the local fields at the boundaries. These local fields are independent of the externally applied condition, and they can be related to the persistence of the small photocurrent observed when a bias voltage higher than the open circuit voltage is applied.