Charge Transport in Deep and Shallow States in a High-Mobility Polymer FET

Polymer FETs generally have a wide subthreshold regime due to a lot of disorder, mainly originated from domain/grain boundaries. Deep state's charge transport of polymer transistors has not been investigated due to the difficulty in determining the field-effect mobility in the subthreshold region. In this paper, the features of the charge transport in deep and shallow states of polymer transistors will be discussed in detail through an accurate modeling and an analysis of subthreshold behavior in transistors. Charge transport in shallow states can be described by multiple trap and release transport, while hopping transport models, such as variable range hopping or Gaussian disorder-based model, describe well the deeper state's charge transport. In addition, the transition between the conduction regimes is a function of temperature and carrier density.