Low-Frequency Noise in TFETs

Abstract: Nanowire tunnel field-effect transistors (TFETs) were investigated by carrying out noise measurements and low-temperature DC measurements. The TFET tunnelling junction was realised by a GaSb/InAs heterojunction resulting in a broken band gap. TFET noise currents were measured at frequencies between 10 Hz and 1 kHz. The results imply that noise in TFETs at the current state of development is dominated by generation-recombination processes caused by traps in the gate oxide. Trap densities between 10^20 cm^-3 eV^-1 and 10^22 cm^-3 eV^-1 were extracted from the noise measurements. The temperature-dependent DC measurements show that the TFETs' off-current is sensitive to the temperature, with lower off-currents at lower temperatures. This indicates that it is not only the tunnelling junction which is governing the off-current. It is concluded that in the devices' off-state electrons can still tunnel into the channel area through the broken band gap but require additional thermionic excitation over the bent channel conduction band to constitute a current.