Effect of biaxial misfit strain on properties of ferroelectric double gate negative capacitance transistors

In order to continue Moore’s law, the reduction of power consumption has received much attention. It is necessary to develop steep devices that can overcome the “Boltzmann tyranny” and solve the problem of high power consumption of integrated circuits. Negative capacitance field-effect transistors are one of the most promising candidates in numerous steep devices. Strain engineering has been widely studied as an effective means of regulating the properties of ferroelectric thin films. However, the influence of strain on the performance of negative capacitance field-effect transistor has not been clear so far. Therefore, in this work, an analytical model of double gate negative capacitance field-effect transistor (DG-NCFET) regulated by biaxial misfit strain is proposed. Using this model, we investigate the influences of ferroelectric layer thickness and biaxial misfit strain on electrical properties of PbZr_0.5Ti_0.5O₃ (PZT)-based and CuInP₂S₆ (CIPS)-based negative capacitance field-effect transistors (NCFETs), respectively. The results show that for the negative capacitance field-effect transistor based on PbZr_0.5Ti_0.5O₃, when the ferroelectric layer thickness is increased or the compression strain is applied, the subthreshold swing and conduction current are improved, but the tensile strain has the opposite effect. For the negative capacitance field-effect transistor based on CuInP₂S₆, its performance is improved when the thickness of the ferroelectric layer is increased or the tensile strain is applied, but the device lags behind under the compressive strain. It is found that the CIPS-based NCFET exhibits better performance than PZT-based NCFET at low gate voltages.