GaN-Based Enhancement-Mode Metal–Oxide–Semiconductor High-Electron Mobility Transistors Using LiNbO3 Ferroelectric Insulator on Gate-Recessed Structure

To fabricate AlGaN/gallium nitride (GaN) enhancement-mode metal-oxide-semiconductor high-electron mobility transistors (E-MOSHEMTs), the gate-recessed structure and the LiNbO₃ ferroelectric film were utilized in this paper. The LiNbO₃ ferroelectric films deposited on the photoelectrochemically etched gate-recessed regions of the AlGaN/GaN E-MOSHEMTs as the gate insulator using a pulsed laser deposition system. The polarization-induced charges of the 2-D electron gas resided on the interface between the AlGaN and GaN layers could be modulated by the C⁺ domains of the crystalline (006) LiNbO₃ ferroelectric films annealed in an oxygen ambience at 600°C for 30 min. When the 15-nm-thick AlGaN was formed in the gate-recessed regions, the threshold voltage and the maximum transconductance of the resulting gate-recessed LiNbO₃/AlGaN/GaN E-MOSHEMTs were +0.40 V and 56.0 mS/mm, respectively. Furthermore, the flicker noise was the dominant noise in the resulting E-MOSHEMTs. The associated normalized low-frequency noise power density of 8.1 × 10¹¹Hz^-1 was measured.