Diffusion effects and "Ballistic transport"

The effects of both collisional drag and diffusion effects on the operation of GaAs n⁺-n-n⁺structures are determined using a momentum transport equation which includes velocity fluctuation effects. It is shown that diffusion effects are important in practical structures, and that previous interpretations of experimental results which claim to show "ballistic" transport can be seriously in error. The general limitations of single-particle transport models when used to try to understand the results of experiments, such as diode characteristic measurements which yield only ensemble averages, are discussed.