Polarization Engineering in PZT/AlGaN/GaN High-Electron-Mobility Transistors

Polarization engineering in 30-nm Pb (Zr,Ti) O
₃
(PZT)/AlGaN/GaN high-electron-mobility transistors (HEMTs) is demonstrated. The coupling between ferroelectric polarization and 2-D electron gas (2DEG) showed a remarkable increase in transconductance during the down-sweep process; this can be attributed to the switching of ferroelectric polarization. With the increase in maximum gate voltage, the transfer curve showed a positive shift; this is because of the increase in polarization charges induced by gate voltage. The drain electric field affected the polarization of ferroelectric layer, leading to different hysteresis behaviors and peak transconductance trends of transfer curves. To decrease the effect of drain electric field on gate, a small drain voltage was used to evaluate the characteristics of PZT/AlGaN/GaN. The variation in peak transconductance was used to estimate the recovery and pinning degree of polarization. The ferroelectric layer modulates the 2DEG in ferroelectric/AlGaN/GaN HEMTs; this mechanism provides guidelines for designing and electrically controlling ferroelectric/AlGaN/GaN HEMTs.