Modulation of sub-threshold properties of InGaAs MOSFETs by La2O3 gate dielectrics

We have found the ferroelectric-like characteristics in atomic layer deposition (ALD) La2O3 films with thermal budget lower than 300oC in polarization-electric field (P-E) and capacitance-gate voltage (C-V) measurements on W/La2O3/W and W/La2O3/InGaAs capacitors. The observed hysteresis and saturation of polarization in the P-E characteristics of the W/La2O3/W and the W/La2O3/InGaAs capacitors, and the counter-clockwise C-V hysteresis in the C-V curves of the W/La2O3/InGaAs capacitors suggest a possibility of ferroelectricity in the present La2O3 films. By using this gate stack, W/La2O3/InGaAs metal-oxide-semiconductor field-effect transistors (MOSFETs) were fabricated in order to examine the negative capacitance (NC) effect due to La2O3. It is found that the sub-threshold swing (SS) of W/La2O3/InGaAs MOSFETs is lower at low temperature than the theoretical limit of MOSFETs. This result strongly suggests that the W/La2O3/InGaAs MOSFETs can work as a steep-slope III-V negative capacitance field-effect transistor (NCFET).