A survey of Gallium Nitride HEMT for RF and high power applications

https://eprints.lib.hokudai.ac.jp/dspace/bitstream/2115/68840/1/1-s2.0-S1369800117317304-main.pdf

State of the art on gate insulation and surface passivation for GaN-based power HEMTs

In this letter, we have proposed a novel AlGaN/GaN FinFET featuring T-shaped gate and extremely linearity of transconductance characteristics ( $\text{G}_{\mathrm {m}})$ . The formation of AlGaN/GaN nano-fins only in the gate opening region is enabled by a developed fabrication process, which is simple and well compatible with the conventional one. When normalized to effective channel width, the fabricated FinFET delivers a 1.45 times higher current density and a 1.66 times higher output power density as high as 11.3 W/mm at 8 GHz compared with the planar HEMTs, along with clearly improved linearity characteristics thanks to a flatter $\text{G}_{\mathrm {m}}$ response afforded by much lower source access resistance. To the best of our knowledge, this is the first demonstration of superior power performance of high-linearity GaN FinFETs, indicating significant advantages of tri-gate configuration over planar HEMTs for microwave power applications.

High-Linearity AlGaN/GaN FinFETs for Microwave Power Applications

This letter reports on the improvement of the large-signal W-band power performance of nitrogen-polar gallium nitride deep recess high electron mobility transistors with the addition of a 40-nm-thick ex-situ silicon nitride passivation layer deposited by plasma enhanced chemical vapor deposition. The additional passivation improves the dispersion control allowing the device to be operated at higher voltages. Continuous-wave load pull measurements performed at 94 GHz on a $2\times 37.5\,\,\mu \text{m}$ transistor demonstrated an improvement in the peak power-added efficiency (PAE) to 30.2% with an associated output power density of 7.2 W/mm at 20 V drain bias. Furthermore, at 23 V, a new record-high W-band power density of 8.84 W/mm (663 mW) was achieved with an associated PAE of 27.0%.

W-Band Power Performance of SiN-Passivated N-Polar GaN Deep Recess HEMTs

Gallium nitride (GaN) is becoming a mainstream semiconductor for power and radio-frequency (RF) applications. While commercial GaN devices are increasingly being adopted in data centers, electric vehicles, consumer electronics, telecom and defense applications, their performance is still far from the intrinsic GaN limit. In the last few years, the fin field-effect transistor (FinFET) and trigate architectures have been leveraged to develop a new generation of GaN power and RF devices, which have continuously advanced the state-of-the-art in the area of microwave and power electronics. Very different from Si digital FinFET devices, GaN FinFETs have allowed for numerous structural innovations based on engineering the two-dimensional-electron gas or p–n junctions, in both lateral and vertical architectures. The superior gate controllability in these fin-based GaN devices has not only allowed higher current on/off ratio, steeper threshold swing, and suppression of short-channel effects, but also enhancement-mode operation, on-resistance reduction, current collapse alleviation, linearity improvement, higher operating frequency, and enhanced thermal management. Several GaN FinFET and trigate device technologies are close to commercialization. This review paper presents a global overview of the reported GaN FinFET and trigate device technologies for RF and power applications, as well as provides in-depth analyses correlating device design parameters to device performance space. The paper concludes with a summary of current challenges and exciting research opportunities in this very dynamic research field.

https://iopscience.iop.org/article/10.1088/1361-6641/abde17/pdf

GaN FinFETs and trigate devices for power and RF applications: review and perspective

The operation of AlGaN/GaN trigate high-electron mobility transistor (HEMT) structures is investigated by numerical simulations. It is shown that the threshold voltage of such structures strongly depends on the width of the AlGaN/GaN bodies and that solely by decreasing the body width a transition from normally-on to normally-off operation can be achieved. Furthermore, the impact of uncertain device and/or material parameters such as strain relaxation, Schottky barrier heights, and dielectric constants on the threshold voltage is studied as well as the influence of the AlGaN barrier design (Al content, thickness). The results of this paper show that the trigate concept is a viable option to realize normally-off AlGaN/GaN HEMTs.

Theoretical Investigation of Trigate AlGaN/GaN HEMTs

Through implementation of the 3-D tri-gate topology, GaN-based high-electron mobility transistors (HEMTs) have been fabricated and high-frequency performances as well as the short-channel effects are investigated. The designed tri-gate transistors are highly-scaled having 100 nm of gate length, which introduces the condition of a short channel. It is demonstrated that higher sub-threshold slopes, reduced drain-induced barrier lowering and better overall off-state performances have been achieved by the nano-channel tri-gate HEMTs with an AlGaN barrier. A lattice-matched InAlGaN barrier with the help of the fin-shaped nano-channels provide improved gate control, increasing current densities, and transconductance $g_{\mathrm{ m}} $ . In a direct comparison, very high drain current densities ( $\sim 3.8$ A/mm) and $g_{\mathrm{ m}} $ ( $\sim 550$ mS/mm) have further been obtained by employing a pure AlN barrier.

High-Current Submicrometer Tri-Gate GaN High-Electron Mobility Transistors With Binary and Quaternary Barriers

The impact of the trigate GaN high electron mobility transistor (HEMT) body geometry on the device RF performance is investigated by 3-D numerical simulations. The trigate concept is a viable approach to achieve normally off operation and to suppress short-channel effects. The effect of gate length scaling on the RF behavior is studied and guidelines for design improvements are provided. Furthermore, it is shown that trigate HEMTs with improved body design and/or InAlN barriers causing a higher polarization charge than AlGaN can exhibit better RF figures of merit than planar GaN HEMTs.

RF Performance of Trigate GaN HEMTs

First-ever realization of a W-band power amplifier (PA) millimeter-wave monolithic integrated circuit (MMIC) utilizing GaN-based Tri-gate high-electron-mobility transistors (HEMTs) is presented in this paper. Superior device- and circuit-level performances over conventional GaN HEMTs are proven to be empowered through implementation of the novel Tri-gate topology which exhibits a 3-dimensional gate profile. The measurements of the fabricated MMIC yield up to 30.6 dBm (1.15 W) of output power in the frequency range of 86–94 GHz with 8% of power-added-efficiency (PAE) and more than 12 dB of transducer power gain. The achieved results demonstrate the promising potential of Tri-gate GaN technology towards high-performance millimeter-wave PA designs.

First demonstration of W-band Tri-gate GaN-HEMT power amplifier MMIC with 30 dBm output power

AlGaN/GaN high-electron mobility transistors (HEMTs) with varied Tri-gate topologies have been fabricated and influences of the fin-shaped nano-channels on device parasitics are examined. Through S-parameter measurements and modelling of the designed Fin-FETs, a detailed RF investigation on intrinsic device parameters is performed under different biasing schemes. Corresponding RF performances and transfer characteristics as well as the derived small-signal parameters of the measured devices are extracted by employing 3-D EM FET model analysis at 110 GHz. Comparisons between the designed fin-geometries and intrinsic device parameters have proven flatter gm, gds and fT responses, which are presented through experimental results in detail for the first time.

Mohamed Alsharef

Papers

Theoretical Investigation of Trigate AlGaN/GaN HEMTs

High-Current Submicrometer Tri-Gate GaN High-Electron Mobility Transistors With Binary and Quaternary Barriers

RF Performance of Trigate GaN HEMTs

First demonstration of W-band Tri-gate GaN-HEMT power amplifier MMIC with 30 dBm output power

Performance and parasitic analysis of sub-micron scaled tri-gate AlGaN/GaN HEMT design