There is a need to understand carrier generation polysilicon TFTs. When the generation is stimulated by the depletion of the material, due to the field effect, carriers are drawn to the surface and move along it by a process akin to diffusion. At some gate voltage the supply of carriers to the channel is insufficient to maintain the current flow. This leads to a reverse bias across the drain junction. It is proposed that carrier generation that occurs mainly near to the drain is more likely to be stimulated by increases of drain rather than gate voltage. The temperature dependence of currents at the current minimum, and at current saturation, of the transfer characteristic are described and are used to justify the model for generation and flow.