Impact of AlScN Gate Dielectric on Electrical Properties of AlScN/AlGaN/GaN Ferroelectric HEMTs

AlGaN/GaN high electron mobility transistors (HEMTs) with Al
1-x
Sc
x
N ferroelectric gate dielectric layer are designed and the impact of gate length, gate thickness, and Sc doping concentration in Al
1-x
Sc
x
N on the electrical properties such as transconductance (G
m
), threshold voltage (V
th
), memory window (ΔV
th
) and subthreshold swing (SS) of GaN-based ferroelectric HEMTs is systematically investigated by using TCAD simulation tools. Simulation results show that both the peak G
m
and ΔV
th
decrease with increasing the gate length. In addition, SS decreases to 135.37 mV/dec as the gate thickness decreases from 90nm to 10nm. The highest performance of the designed HEMTs is obtained with an optimized Al
1-x
Sc
x
N ferroelectric layer with the gate length of 0.6 μm, the gate thickness of 10 nm, and the Sc doping concentration of 0.20, resulting in a maximum memory window of 3.111 V and a minimum subthreshold swing of 131.11 mV/dec. The enhancement may be caused by excellent ferroelectric properties of AlScN layer. These finding pave the way for ferroelectric-enhanced transistors based on nitrides.