In this paper, we report state-of-the-art high frequency performance of GaN-based high electron mobility transistors (HEMTs) and Schottky diodes achieved through innovative device scaling ...technologies such as vertically scaled enhancement and depletion mode (E/D mode) AlN/GaN/AlGaN double-heterojunction HEMT epitaxial structures, a low-resistance n + -GaN/2DEG ohmic contact regrown by MBE, a manufacturable 20-nm symmetric and asymmetric self-aligned-gate process, and a lateral metal/2DEG Schottky contact. As a result of proportional scaling of intrinsic and parasitic delays, an ultrahigh f T exceeding 450 GHz (with a simultaneous f max of 440 GHz) and a f max close to 600 GHz (with a simultaneous f T of 310 GHz) are obtained in deeply scaled GaN HEMTs while maintaining superior Johnson figure of merit. Because of their extremely low on-resistance and high gain at low drain voltages, the devices exhibited excellent noise performance at low power. 501-stage direct-coupled field-effect transistor logic ring oscillator circuits are successfully fabricated with high yield and high uniformity, demonstrating the feasibility of GaN-based E/D-mode integrated circuits with transistors. Furthermore, self-aligned GaN Schottky diodes with a lateral metal/2DEG Schottky contact and a 2DEG/ n + -GaN ohmic contact exhibited RC-limited cutoff frequencies of up to 2.0 THz.
In this letter, we discuss a novel asymmetric field plate structure utilizing a slanted field plate (FP) engineered to appropriately distribute the electric field on GaN high-electron mobility ...transistors (HEMTs) scaled for low-loss, high-speed power switch applications. A uniform electric field distribution achieved with the slant FP enables an optimum device design, where a low-dynamic ON-resistance (R on,dyn ) and high breakdown voltage are obtained simultaneously by minimizing the gate-drain distance. The optimized FP design demonstrated a low R on,dyn of 2.3 (2.1) Ω-mm at a quiescent drain voltage of 50V in E-mode (D-mode) HEMTs with a breakdown voltage of 138 V (146 V). The corresponding high-frequency performance of E-mode (D-mode) HEMTs of peak f T /f max = 41/100 GHz (53/100 GHz) yielded a decent R on,dyn ×Qg product in the range of 31.0-34.5 (28.0-33.3) mQ-nC. This new slant FP technology combined with scaled epitaxial structure (for short L g ) and reduced access resistances, using n+ GaN ohmic contacts, greatly enhances performance and design flexibility of high-speed, low-loss, GaN power switch devices.
W-band, 5W solid-state power amplifier/combiner Schellenberg, James; Watkins, Edward; Micovic, Miroslav ...
2010 IEEE MTT-S International Microwave Symposium,
05/2010
Conference Proceeding
This paper reports a W-band solid-state power amplifier with an output power of 5.2W at 95 GHz and greater than 3 watts over the 94 to 98.5 GHz band. These SOA results were achieved by combining 12 ...GaN MMICs in a low-loss radial-line combiner network. The 12-way combiner demonstrates an overall combining efficiency of 87.5%, and excluding combiner conductor losses (0.3 dB), exhibits a combining efficiency of 93.7% at 95GHz. The size of the 12-way amplifier/combiner is only 2.39" dia. × 1.5" length. This work represents the first application of the radial-line combiner configuration to applications at W-band frequencies, and establishes new levels of performance for solid-state power amplifiers operating at these frequencies.
This letter reports record RF performance of deeply scaled depletion-mode GaN-high-electron-mobility transistors (GaN-HEMTs). Based on double heterojunction AlN/GaN/AlGaN epitaxial structure, fully ...passivated devices were fabricated by self-aligned-gate technology featuring recessed n + -GaN ohmic contact regrown by molecular beam epitaxy. Record-high f T of 454 GHz and simultaneous f max of 444 GHz were achieved on a 20-nm gate HEMT with 50-nm-wide gate- source and gate-drain separation. With an OFF-state breakdown voltage of 10 V, the Johnson figure of merit of this device reaches 4.5 THz-V, representing the state-of-the-art performance of GaN transistor technology to-date. Compared with previous E-mode GaN-HEMTs of similar device structure, significantly reduced extrinsic gate capacitance and enhanced average electron velocity are the key reasons for improved frequency characteristic.
Self-Aligned AlGaN/GaN FinFETs Brown, David F.; Yan Tang; Regan, Dean ...
IEEE electron device letters,
2017-Oct., 2017-10-00, Letnik:
38, Številka:
10
Journal Article
Recenzirano
We have demonstrated highly scaled, self-aligned AlGaN/GaN fin-shaped field-effect transistors (FinFETs), which were fabricated using e-beam lithography and a regrown n+ GaN ohmic process with a ...sacrificial dummy gate. Our devices were very aggressively scaled, with fin widths, gate length, and source drain spacing as small as 50,60, and 200 nm, respectively.DC characteristics, when normalized to active device periphery (number of fins times fin width), showed peak transconductance of 1.5 mS/μm and ON resistance of 390 Ω-μm. Enhancement mode device operation was observed for fin widths below 100 nm.
HRL's T3 GaN MMIC technology is evaluated using dc reliability experiments, including a voltage step-stress test, a temperature step-stress test, and a 3-temperature life test. The drain voltage ...step-stress test revealed three distinct regions of operation through gate leakage characteristic changes: burn-in stabilization up to 5 V, followed by stable operation up to 20 V, then voltage-dependent degradation up to catastrophic failure around 30 V. As a result, a de-rated recommended safe-operating limit of Vds = 12 V was established. The temperature step-stress test resulted in clear Arrhenius temperature-dependent degradation of the device on-resistance above 250 °C. Similarly, a recommended safe-operating limit of 150 °C was established for the technology. Finally, the 3-temperature life test resulted in clear temperature group separation and an activation energy of 2.52 eV, with a mean time-to-failure of 4 million hours at 150 °C with only a +0.2 ohm.mm increase in device on-resistance. Physical failure analysis of degraded parts showed the mechanism was a defect formation in the epitaxial barrier layer at the drain edge of the gate. Finite-element electrical simulations duplicated this degradation mechanism by modeling the defect as a void, which depleted the 2DEG and therefore increased device on-resistance.
High-performing GaN MMICs that can cover broadband applications at W and D-Band have been fabricated and tested. A five stage 60-105 GHz LNA has >23 dB of gain across the band and a six stage D-Band ...LNA has 25 dB of gain from 110-170 GHz. A double balanced resistive FET mixer has -11 to -15 dB of conversion loss from 74-94 GHz. To our knowledge, these are the first reported GaN MMICs with high broadband gain at these frequencies.
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