Influence of mobility fluctuations on random telegraph signal amplitude in n-channel metal-oxide-semiconductor field-effect transistors

The amplitude of random telegraph signals (RTS) in an n-channel metal-oxide-semiconductor field-effect transistor has been investigated. Current fluctuations originating when a single-channel electron is trapped or detrapped in the silicon dioxide have been evaluated. A simulation has been performed where the inversion-layer quantization, the dependence of the electron mobility on the transverse and longitudinal electric fields, and the influence of the oxide charges on free-carrier density and on electron mobility have been taken into account. This procedure provides the chance of studying the influence of trap depth in the oxide on the RTS amplitude. In addition, the contributions of the mobility and carrier fluctuations on the amplitude of discrete current switching have been separated, revealing the importance of each factor. Normalized mobility fluctuation has been defined and it was found that its dependence on the gate and drain voltages helped to explain the behavior of the normalized current fluctuations. Finally, the scattering coefficient was evaluated, showing good agreement with previously published data. All these results have allowed us to gain further insight into the role played by electron mobility fluctuations on random telegraph signal amplitude. (C) 1997 American Institute of Physics. [S0021-8979(97)00421-0].