Ferroelectric Polarization Enabled Threshold Voltage Modulation in High Electron Mobility Transistor

ABSTRACT

Integrating ferroelectric thin films into the gate stack of high electron mobility transistors (HEMTs) would enable modulation of the threshold voltage (V _th ) and, ultimately, switching between depletion (D)‐ and enhancement (E)‐mode within the same HEMT. However, the experimental range over which V _th can be modulated is often substantially smaller than that expected from the coercive voltage. A comprehensive model for complete control over the interplay between ferroelectric switching and HEMT operation is presented, considering a versatile ferroelectric‐metal‐HEMT (FeMHEMT) configuration. The proposed model delivers quantitative predictions of achievable V _th values in relation to the ferroelectric polarization orientation, which are verified through a modular approach of connecting ferroelectric capacitors to metal‐insulator‐semiconductor (MIS) HEMTs. Essential guidelines for integrating wurtzite‐ and fluorite‐structured ferroelectrics with HEMTs at their full potential are presented. The area ratio between the ferroelectric and MIS capacitors is identified as a crucial parameter for achieving complete polarization reversal without MIS breakdown, especially for wurtzite‐structured ferroelectrics. Comparing hafnium zirconium oxide and aluminium scandium nitride, the role played by the charge injected into the floating gate on the FeMHEMT operation is elucidated. A remarkably large memory window of 37.6 V is experimentally demonstrated while switching between D‐ and E‐mode within the same FeMHEMT.