Peculiarities of the SCLC Effect in Gate-All-Around Silicon Nanowire Field-Effect Transistor Biosensors

High-quality liquid gate-all-around (LGAA) silicon nanowire (NW) field-effect transistor (FET) biosensors are fabricated and studied their properties in 1 mm phosphate-buffered saline solution with pH = 7.4 using transport and noise spectroscopy. At small V-DS, the conventional current behavior of FET with a linear dependence on voltage is registered in the output current-voltage (I-V-M) characteristics with M = 1. At drain-source voltage V-DS > 0.6 V, the I-V characteristics with stronger power M are revealed. It is shown that the current in LGAA NW FETs follows current proportional to voltage in power M = 4 dependence on small liquid gate voltages. Transport and noise spectroscopy analyses demonstrate that the obtained results are associated with the space-charge-limited current (SCLC) effect. Moreover, a strong two-level random telegraph signal (RTS) is found in the region corresponding to SCLC at V-DS values exceeding 0.6 V. The RTS related to single trap phenomena results in a well-resolved Lorentzian component of noise spectra. The results demonstrate that the SCLC and two-level RTS phenomenon are correlated effects. They should be taken into account during the development of single-trap-based devices, including biosensors.