Back-Gate Fully Depleted Silicon-on-Insulator P-Channel Schottky Barrier MOSFET With Ultrahigh Voltage Sensitivity for Label-Free Virus RNA Detection

This work reports a planar fully depleted silicon-on-insulator (FDSOI) p-channel Schottky barrier (SB) metal–oxide–semiconductor field-effect transistor (MOSFET) for ORF1ab RNA gene detection RNA field-effect transistor (RNAFET). The gold nanoparticle/high-K hafnium dioxide/FDSOI SB-PMOSFET biosensor with ultrahigh voltage sensitivity is demonstrated. It is measured by the inherent back gate without a liquid-gate electrode. The very thin top-Si channel of FDSOI requires the metal source/drain (S/D) contact rather than the ion implantation doping to avoid ion penetration in the buried oxide (BOX) layer, which helps to obtain a good bake-gate RNAFET biosensor to achieve the high voltage sensitivity. The back-gate measurement operation can amplify the voltage readout response through the strong capacitive coupling effect of double-gate device itself, thus significantly improving the detection sensitivity but without additional amplifying circuitry. For the RNAFET biosensor, the hybridization between the charged ribonucleic acid (RNA) analyte and the complementary probe deoxyribonucleic acid (DNA) can shift the device threshold voltage ( $V_{\mathrm {th}}$ ). It shows that the back-gate $V_{\mathrm {th}}$ sensitivity can actually be up to 1.765 V/log[RNA] for ORF1ab gene detection, which is ~100 times improvement over a conventional liquid-gate Si MOSFET DNA biosensor.