Fabrication and Characterization of Enhancement-Mode AlGaN/GaN Fin-Shaped Metal-Oxide-Semiconductor High-Electron Mobility Transistors
Date Issued
2015
Date
2015
Author(s)
Yeh, Po-Chun
Abstract
In this thesis, we present an enhancement-mode AlGaN/GaN fin-shaped metal-oxide-semiconductor high-electron mobility transistors (MOS-HEMT), fabricated by combining gate recess process and fin-shape structure, featuring double-layer oxides composed of photo-enhanced-chemical (PEC) oxidation and plasma-enhanced atomic layer deposition (PE-ALD) oxide, which was shown to support threshold voltage (Vth) with a linear slope of 0.36 V/nm and -0.32 V/μm2, respectively, scaled with recess depth and device area. The proposed device exhibited Vth = 1.2V, current on/off ratio of 10^8, and cutoff frequency of unity current gain/power gain (fT/fmax) = 9/36GHz at gate length/width = 250/360nm. These observations can be ascribed to the combination effects of (a) interfacial negative space charge of 3.2 μC/cm2 in the gate-recessed device to partially compensate the polarization charges, and (b) side-wall passivation to preserve the high mobility channel.
Subjects
Transistor
Fin-Shaped
GaN
Enhancement-Mode
MOS-HEMT
Type
thesis
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