Transit currents in a one-dimensional polymer single crystal

Abstract

Time-of-flight experiments are performed on the one-dimensional semiconductor single-crystal PDATS using localized carrier generation on the (100) face. The authors present new results and conclusions based on these techniques. Carrier velocities are found to be field dependent, acoustic and trap limited with an inter-trap separation of 15 mu m or less. A simple model is proposed to explain this field dependence and is based on the premise that the intrinsic motion of the negative carriers is that of a solitary wave acoustic polaron as advanced by Wilson, but whose observed motion is dominated by shallow, field-dependent traps with trap release times at room temperature that are inversely proportional to field. Time-of-flight signals for holes were not observed and it is concluded therefore that the electrons are the dominant current carriers. Also, the length dependence of the transit times is found to be linear, suggesting that electron propagation is Gaussian. Finally, the effects of electrode geometry and charge density on field are considered.