Abstract
An enhancement-mode AlGaN/GaN metal-insulator-semiconductor high-electron- mobility-transistor was fabricated using a recess gate and CF4 plasma treatment to investigate its reliable applicability to high-power devices and circuits. The fluorinated-gate device showed hysteresis during the DC current-voltage measurement, and the polarity and magnitude of hysteresis depend on the drain voltage. The hysteresis phenomenon is due to the electron trapping at the Al2O3/AlGaN interface and charging times longer than milliseconds were obtained by pulse I-V measurement. In addition, the subthreshold slope of the fluorinated-gate device was increased after the positive gate bias stress because of the two-dimensional electron gas reduction by ionized fluorine. Our systematic observation revealed that the effect of fluorine ions should be considered for the design of AlGaN/GaN power circuits.
Highlights
AlGaN/GaN high electron mobility transistors (HEMTs) have recently demonstrated to be excellent devices for high-frequency and high-power electronics, thanks to the high breakdown voltage [1] and the low on-state resistance [2] and gate leakage [3]
We demonstrated that the cause of hysteresis was the charge trapping/detrapping effect introduced at the dielectric (Al2O3) and fluorinated AlGaN interface and gate leakage characteristics corresponding to VD
The AlGaN/GaN heterostructure was grown by metal-organic chemical vapor deposition (MOCVD) on a sapphire substrate, which consists of a 21-nm AlGaN (26% Al) barrier with a 2-nm GaN cap layer
Summary
AlGaN/GaN high electron mobility transistors (HEMTs) have recently demonstrated to be excellent devices for high-frequency and high-power electronics, thanks to the high breakdown voltage [1] and the low on-state resistance [2] and gate leakage [3]. The AlGaN barrier recess and fluorine ion implantation methods had been widely studied to shift the VT in the positive direction. These methods modulate the VT, the gate modifications introduce side effects resulting from the surface damage during the device fabrication process [10,11,12], and the electrical and frequency characteristics are degraded due to the poor interface conditions [13]. We demonstrated that the cause of hysteresis was the charge trapping/detrapping effect introduced at the dielectric (Al2O3) and fluorinated AlGaN interface and gate leakage characteristics corresponding to VD. We have revealed the effect of fluorine treatment on the dielectric/AlGaN and AlGaN/GaN interfaces through experimental evidence
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