Ferroelectric domain modulated AlGaN/GaN field effect transistor

Abstract

A two-dimensional electron gas (2DEG) in (Al, Ga) N/GaN heterojunction (AlGaN/GaN) is a key factor that affects the performance of GaN-based high electron mobility transistor (HEMT) devices. Previous studies have shown that the ferroelectric polarization can effectively control the density of the 2DEG at the AlGaN/GaN interface; however, the correlation between two-dimensional distribution of ferroelectric polarization (i.e., ferroelectric domains) and its ability to confine the 2DEG is yet to be investigated. In this work, ferroelectric domain-induced modulation of the 2DEG in the AlGaN/GaN heterostructure was characterized using microscopic as well as local transport measurement techniques. The results suggest direct evidence for effective ferroelectric domain engineering in GaN HEMTs, as predicted by theoretical calculations. Additionally, a prototype device was fabricated, where gating was realized by utilizing the polarization of the ferroelectric domain. Considering the nonvolatile and reconfigurable advantages of a ferroelectric domain, the E-mode, D-mode, and even multi-channel output characteristics were realized in the same device by artificially engineered ferroelectric domain structures. These results offer a promising solution for the contradiction between the 2DEG density and gate controllability in GaN HEMTs, thereby showing a great potential of GaN radio frequency devices with further scaled gate lengths down to a few nanometers in the future.