A study of the kink-related excess low-frequency noise in silicon- on-insulator n-metal-oxide-semiconductor transistors operated at liquid helium temperatures

In this paper, the drain voltage dependence of the low-frequency (lf) noise of partially depleted silicon-on-insulator n-metal-oxide-semiconductor-transistors (n-MOSTs) is investigated in detail at liquid helium temperature. As will be shown, an increase in the noise spectral density is observed at the kink position, similar to bulk n-MOSTs operated at 4.2 K. This excess noise introduces a Lorentzian generation-recombination (GR) component in the lf noise spectrum. The physical mechanism underlying the GR noise is thought to be the same as for bulk transistors: ionization and capture in the depletion region of carriers, which are created at the drain. This generates a fluctuation in the depletion charge, which is translated into a fluctuation of the drain current via a change in the threshold voltage. A model will be proposed that is derived from the analysis previously established for the bulk case. Extension of the model to fully depleted, thin-film transistors and to higher temperatures (77 K, 300 K) will be briefly outlined. As will be demonstrated, a good overall agreement between theory and experiment is obtained whereby the key features of the noise overshoot, i.e., its position and amplitude, are consistently reproduced.