Physical mechanism of current fluctuation under ultra-small device structures

Monte Carlo analyses of the current fluctuation in Si n-i-n structures have been carried out by varying the length of the i (channel) region so that the diffusive to quasi-ballistic transport is covered. It has been demonstrated that the current fluctuation is dominated by thermal noise at low bias regions and makes a direct transition to hot carrier noise in moderately large devices. On the other hand, a new fluctuation mode appears under sub-0.1 micron device structures. This is associated with the fluctuation of the electron number in the i (channel) region and results from both the ballistic electrons emitted from the left n (source) region and the electrons diffused from the right n (drain) region.