Abstract
AlGaN/GaN high-electron-mobility transistors (HEMTs) with Hr0.5 Zr0.5O2 ferroelectric gate stacks exhibiting significant ferroelectric switching for threshold voltage control are experimentally demonstrated. Ferroelectric gate HEMTs (FeHEMTs) with large threshold voltage tuning range of 2.8 V were obtained, with an on/off ratio of $\sim {10}^{{{5}}}$ based on a GaN-channel HEMT structure suitable for RF applications. Improved subthreshold performance has also been achieved compared to conventional MIS-HEMTs, with reduction in average sub-threshold swing (SSavg) by a factor of 2. As a consequence of the significant ferroelectric polarization achieved on AlGaN/GaN heterostructures, Hr0.5 Zr0.5O2 based ferroelectric gate AlGaN/GaN HEMTs appear promising for nonvolatile and reconfigurable RF and microwave applications.
Highlights
F ERROELECTRIC (FE) devices have attracted much attention for their potential application to a wide range of uses, including memory, steep slope transistors, and neuromorphic computing [1]–[3]
The results provide insights into routes for exploitation of FE gate stacks on GaN and related materials for nonvolatile RF and microwave applications
A higher average SS was observed for forward sweeps for ferroelectric gate HEMTs (FeHEMTs) with thinner Al2O3 layer, which may be due to the increased susceptibility to non-uniform FE switching from the degraded interfacial uniformity as well as higher gate fields
Summary
F ERROELECTRIC (FE) devices have attracted much attention for their potential application to a wide range of uses, including memory, steep slope transistors, and neuromorphic computing [1]–[3]. Extensive research has been devoted to FE devices on silicon, including evaluation of ferroelectric devices for possible low-voltage performance optimization and nonvolatile memory applications [4]–[6]. An area of particular interest and potential impact is the combination of ferroelectric materials with III-nitrides; the strong polarization of nitrides [7] along with the switchable polarization nature of ferroelectrics [8], [9] can be used to augment polarization engineering for 2D-electron gas (2DEG) channel modulation and dynamic threshold voltage control, opening up potential for multifunctional semiconductor devices for nonvolatile and reconfigurable RF/microwave applications [10]–[12]. Color versions of one or more of the figures in this letter are available online at http://ieeexplore.ieee.org. Prior reports of devices with FE gate stacks on GaN-based HEMTs have focused on achieving enhancement-mode operation or steeper subthreshold performance [13]–[17]. Hf0.5Zr0.5O2(HZO) based ferroelectric gate HEMTs (FeHEMTs) on AlGaN/GaN heterostructures have been experimentally demonstrated. The results provide insights into routes for exploitation of FE gate stacks on GaN and related materials for nonvolatile RF and microwave applications
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