Nanometer-scale transistors based on III-V compound semiconductors, such as GaAs, InAs, and InP, are at the heart of many high-speed and high-frequency electronic systems 10. Due to their high electron mobilities, these devices exhibit very high small-signal cutoff frequencies, in the terahertz range 11. However, the high-frequency large-signal performance of transistors is still a challenge, since it is severely limited by the output capacitance Cout, electron saturation velocity and critical electric field 12. The maximum switching speed of a transistor (Fig. 1a) with saturation current Imax is limited to performance semiconductor materials. GaAs and InP are limited to the JFOM, while Cout-limited rise-rate of 1 V/ps restricts the performance of SiC, GaN, and Diamond.
Abstract-Enhanced performance in AlGaN/GaN Schottky barrier diodes (SBDs) is investigated using a nanowire hybrid tri-anode structure that integrates three-dimensional Schottky junctions with tri-gate transistors. The fabricated SBDs presented an increased output current density with improved linearity, above 1 A/mm at 5 V when normalized by effective anode width, over 3 orders of magnitude lower reverse leakage current and superior heat dissipation. The sidewall Schottky contacts reduced the turn-on voltage and eliminated the non-ideality caused by the AlGaN barrier. The large surface area of tri-gate architecture greatly enhanced heat dissipation and largely reduced the average temperature as well as thermal resistance of the integrated tri-gate transistors. The trench conduction near SiO2/GaN interface, formed under forward bias at both sidewalls and bottom of nanowire trenches, compensated part of the self-heating degradation and improved the output linearity of the device. Optimal design for the tri-anode structure, based on a model of critical filling factor, was proposed to surmount the issue of partial removal of two-dimensional electron gas (2DEG), unveiling the potential of nanostructured GaN devices to achieve comparable or even larger output current than counterpart planar devices.
In this paper, we present a detailed investiga-1 tion of the impact of fin width (w fin) on tri-gate AlGaN/GaN 2 metal-oxide-semiconductor high electron mobility transis-3 tors (MOSHEMTs). As w fin is reduced, the threshold volt-4 age (V TH) increases, which is due to the enhanced gate 5 control (especially for w fin < 200 nm) thanks to the 3-D 6 geometry of the tri-gate, and the reduced carrier concen-7 tration (N s) caused by a more pronounced strain relax-8 ation and sidewall depletion, as explored using Hall and 9 capacitance-voltage (C-V) measurements. The normally-10 OFF operation was achieved for w fin close to the sidewall 11 depletion width (w dep) of 19.5 nm, since the fin is depleted 12 from its two sidewalls. The impact of w fin on ON-resistance 13 (R ON) and current capability (I D,max) was also investigated, 14 along with the influence of the effective source injection, 15 the trench conduction and the filling factor (FF) on these 16 key characteristics. The degradation caused by the tri-gate 17 fin etching could be fully recovered by increasing the FF. 18 Finally, we show that the tri-gate can reduce gate capac-19 itance (C G) and charge (Q G) in normally-ON MOSHEMTs, 20 depending on the design of the tri-gate and the gate voltage 21 (V G), leading to a smaller R ON • Q G product that is benefi-22 cial for high-frequency switching applications. The results 23 in this paper offer insights into important phenomena in 24 tri-gate GaN devices and are fundamental for the further 25 advance of this technology. 26 Index Terms-Drain current, fin width, GaN, gate capaci-27 tance, threshold voltage, tri-gate. 28 I. INTRODUCTION 29 T RI-GATE technologies have recently attracted consider-30 able attention for lateral GaN electronic devices [1]-[20], 31 thanks to many advantages over conventional planar gates. 32 First, the V TH in tri-gate GaN metal-oxide-semiconductor 33 high electron mobility transistors (MOSHEMTs) increases 34 as w fin decreases, hence, the normally-OFF operation can be 35
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