Substitution of Paraelectric for Conventional Dielectric in AlGaN/GaN MISFETs

A ferroelectric material of paraelectric state is proposed as a substitute for the conventional dielectric in AlGaN/GaN metal-insulator-semiconductor field-effect transistors (MISFETs). Owing to its switchable polarization, the maximum transconductance of a barium strontium titanate (BST)/AlGaN/GaN metal-paraelectric-semiconductor FET (MPSFET) is significantly improved by 44% as compared to a conventional SiN/AlGaN/GaN MISFET. The pinchoff voltage is greatly reduced from -10.7 V for the MISFET to -4.7 V for the MPSFET, accompanied with a distinct improvement in the pinchoff characteristics and suppression of soft pinchoff. Small-signal measurements result a comparable frequency performance of the FETs with BST and SiN gate dielectrics. Based on a self-consistent calculation, the switchable polar nature of the paraelectric is revealed to be essential for improving the device transconductance.