We report preliminary measurements of transient drain current undershoot with time constants of the order of milliseconds in thick and highly doped n-type junctionless fieldeffect transistors. This effect might be attributed to a process involving generation of holes in the n-type-doped channel, which can also explain the partial channel depletion as consequence of channel screening by an inversion layer, thus impeding the device to be switched off. The approach described in this work could also be used for characterization of silicon channels in junctionless nanowires.