Gate-Localized Fluorination Enables Enhancement-Mode AlGaN/GaN High-Electron Mobility Transistors 32 views

Gallium nitride (GaN)-based high-electron-mobility transistors (HEMTs) are key to high-power and high frequency electronics owing to their wide bandgap, high breakdown field, and ability to form a high-density two-dimensional electron gas (2DEG) at the AlGaN/GaN interface. For power-switching systems, enhancement-mode (E-mode) operation, where devices remain normally off at zero gate bias, is preferred for intrinsic failsafe behavior and reduced standby power. However, conventional E-mode strategies, such as deep gate recessing or p-type gate insertion, often introduce fabrication complexity, surface damage and long-term instability. Here, we demonstrate a gate-localized CHF3 plasma process that simultaneously produces a self-limiting recess with fluorine terminated surface, enabling normally-off AlGaN/GaN HEMT. Fluorine incorporation compensates polarization-induced charges and drives a positive shift in threshold voltage (Vth), whereas hydrogen species generated during plasma exposure passivate etch-induced Ga-related defects and suppress interface-trap formation. By confining plasma exposure to the gate region, this method mitigates surface degradation and charge trapping typically observed with CF4 processing, achieving precise and stable Vth control without deep gate recessing. The fabricated devices exhibit normally-off operation while maintaining low gate leakage under bias stress. This single step, lithographically confined approach offers a practical route toward E-mode GaN HEMTs for energy-efficient, high-frequency and high-power electronic systems.

MS (Master of Science)

AlGaN/GaN HEMTs; Enhancement-Mode Operation; CHF3 Plasma Treatment; Threshold Voltage Engineering

English

All rights reserved by the author (no additional license for public reuse)

2026-04-15