Negative capacitance in ferroelectric heterostructures

Negative capacitance can enable ultralow-power field effect transistors, though the concept of ferroelectric negative capacitance, especially its stability, remains contentious. We resolve this issue here by analyzing ferroelectric/dielectric heterostructure rigorously using the Landau-Denvonshire theory, identifying three critical dielectric thicknesses upon which the stability of negative capacitance changes. A critical electric window is also identified, beyond which stable negative capacitance cannot be maintained. Between the first and second critical thicknesses, metastable negative capacitance exists, yet it will be lost and cannot be recovered once the electric window is broken. Between the second and third critical thicknesses, negative capacitance is always stable within the electric window, resulting in hysteretic double P-E loop. Beyond the third critical thickness, P-E loop becomes hysteresis free. Singularities in the effective dielectric constant are also observed at the critical thickness or electric field.