C. McGuire

Epitaxial-Graphene RF Field-Effect Transistors on Si-Face 6H-SiC Substrates

We report dc and the first-ever measured small-signal radio-frequency (RF) performance of epitaxial-graphene RF field-effect transistors (FETs), where the epitaxial-graphene layer is formed by graphitization of 2-in-diameter Si-face semi-insulating 6H-SiC (0001) substrates. The gate is processed with a metal gate on top of a high-k Al2 O3 gate dielectric deposited via an atomic-layer-deposition method. With a gate length (Lg) of 2 mum and an extrinsic transconductance of 148 mS/mm, the extrinsic current-gain cutoff frequency (fT) is measured as 4.4 GHz, yielding an extrinsic fT ldr Lg of 8.8 GHz middot mum. This is comparable to that of Si NMOS. With graphene FETs fabricated in a layout similar to those of Si n-MOSFETs, on-state current density increases dramatically to as high as 1.18 A/mm at Vds = 1 V and 3 A/mm at Vds = 5 V. The current drive level is the highest ever observed in any semiconductor FETs.

55% PAE and High Power Ka-Band GaN HEMTs With Linearized Transconductance via

We report small- and large-signal performances of 140-nm gatelength field-plated GaN HEMTs at Ka-band frequencies, in which the GaN HEMTs were fabricated with n+ source contact ledge. The parasitic channel resistance is reduced by ~ 50%, whereas the peak extrinsic transconductance is improved by 20% from 370 to 445 mS/mm. The GaN HEMTs with n+ source ledge exhibit improvement of maximum stable gain by at least 0.7 dB over reference devices without n+ ledge. At 30 GHz, CW output power density of 10 W/mm is measured with peak PAE of 40% and associated gain of 8.4 dB at Vds = 42 V. At Vds = 30 V, the output power density is measured as 7.3 W/mm with peak PAE of 50%, peak DE of 58%, and associated gain of 8.5 dB. The best PAE was measured as 55% at 5 W/mm at 30, 33, and 36 GHz, where the associated gains were 7.9, 7.6, and 8.2 dB, respectively.

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In this letter, we present the first graphene FET operation for zero-bias resistive FET mixers, utilizing modulation of graphene channel resistance rather than ambipolar mixer operations, up to 20 GHz. The graphene FETs with a gate length of 0.25 μm have an extrinsic cutoff frequency fT of 40 GHz and a maximum oscillation frequency fMAX of 37 GHz. At 2 GHz, the graphene FETs show a conversion loss of 14 dB with gate-pumped resistive FET mixing, with at least > 10-dB improvement over reported graphene mixers. The input third-order intercept points (IIP3s) of 27 dBm are demonstrated at a local oscillator (LO) power of 2.6 dBm. The excellent linearity demonstrated by graphene FETs at low LO power offers the potential for high-quality linear mixers.

GaN Source Contact Ledge

Highly scaled GaN T-gate technology offers devices with high ft/fMAX, and low minimum noise figure while still maintaining high breakdown voltage and high linearity typical for GaN technology. In this paper we report an E-band GaN power amplifier (PA) with output power (Pout) of 1.3 W at power added efficiency (PAE) of 27% and a 65-110 GHz ultra-wideband low noise amplifier (LNA). We also report the first G-band GaN amplifier capable of producing output power density of 296mW/mm at 180 GHz. All these components were realized with a 40 nm T-gate process (ft= 200 GHz, fMAX= 400 GHz, Vbrk > 40V) which can enable the next generation of transmitter and receiver components that meet or exceed performance reported by competing device technologies while maintaining > 5x higher breakdown voltage, higher linearity, dynamic range and RF survivability.

Graphene FETs for Zero-Bias Linear Resistive FET Mixers

We report the DC and switching performance of a normally-off 5A/1100V GaN-on-Si device. The device had a breakdown field of 95V/µm and a V<inf>B</inf>²/R<inf>on,sp</inf> of 272MW/cm². A 360V/180W boost converter was operated at 200KHz, with an efficiency ≫92%. Respectively, these values are the highest for a normally-off GaN-on-Si device.

GaN Technology for E, W and G-Band Applications

We have demonstrated 8.5-11.5 GHz class-E MMIC high-power amplifiers (HPAs) with a peak power-added-efficiency (PAE) of 61% and drain efficiency (DE) of 70% with an output power of 3.7 W in a continuous-mode operation. At 5 W output power, PAE and DE of 58% and 67% are measured, respectively, which implies MMIC power density of 5 W/mm at Vds = 30 V. The peak gain is 11 dB, with an associated gain of 9 dB at the peak PAE. At an output power of 9 W, DE and PAE of 59% and 51 % were measured, respectively. In order to improve the linearity, we have designed and simulated X-band class-E MMIC PAs similar to a Doherty configuration. The Doherty-based class-E amplifiers show an excellent cancellation of a third-order intermodulation product (IM3), which improved the simulated two-tone linearity C/IM3 to >; 50 dBc.

Normally-off 5A/1100V GaN-on-silicon device for high voltage applications

A W-band monolithic microwave integrated circuit (MMIC), including an Sb-heterostructure diode on a GaAs substrate, has been demonstrated. The MMIC also includes the RF choke and output shorting capacitor essential to detector circuits. Additional input matching has yielded peak sensitivities on the order of 10 000 V/W and equivalent bandwidths of 40 GHz. Using these circuits in conjunction with current W-band low-noise amplifier technology can achieve the sub-1degK noise equivalent temperature difference necessary for producing discernible images with W-band passive imaging cameras.

High efficiency X-band class-E GaN MMIC high-power amplifiers

We report the state-of-the-art performance of deep-submicrometer gate length dual-gate GaN HEMTs and cascode GaN HEMTs with 10× reduced gate-to-drain feedback capacitance compared with single-gate GaN HEMTs. With 150-nm gate length field-plated gate structures, these GaN HEMTs demonstrated improvement of small-signal gain by 10 dB, compared with single-gate GaN HEMTs. Large-signal load-pull measurements showed peak power-added-efficiency (PAE) of 71%-74% without harmonic tuning at 10 GHz, up to a measured continuous-wave output power level of 2.3-2.5 W. The 74% PAE is very close to a theoretical maximum PAE of 78.5% without harmonic tuning. Compared with single-gate GaN HEMTs, both the dual-gate and cascode GaN HEMTs offer~10% improvement in peak PAE at the output power of 2.3-2.5 W.

W-Band Sb-Diode Detector MMICs for Passive Millimeter Wave Imaging

In this letter, we report the state-of-the-art micro wave noise performance of discrete 0.15-μm-gate-length field plated (FP) GaN HEMTs. The FP GaN HEMTs yielded a peak fτ/fmax of 60 GHz/150 GHz at Vds = 10 V. An fmax of 230 GHz was obtained at Vds = 20 V. At 2.5 V, the source-drain bias and dc power dissipation of 200 mW/mm, a minimum noise figure (NFmin) of 0.89 dB, and an associated gain (AG) of 11 dB were measured at 10 GHz. At 20 GHz the NFmin and AG were 1.9 and 6.2 dB, respectively. The sub-1-dB microwave noise performance at 10 GHz is the best ever reported for FP high-power GaN HEMTs, which can be attributed to their lateral scaling and deep-submicrometer gate lengths.

>70% Power-Added-Efficiency Dual-Gate, Cascode GaN HEMTs Without Harmonic Tuning

We report on multi-octave (100 MHz - 8 GHz) GaN HEMT nonuniform distributed amplifier (NDPA) with and without linearization in a MMIC architecture for the first time. The NDPAs were fabricated with 0.14-μm field-plate AlGaN/GaN HEMT technology with fT of 58 GHz and breakdown voltage of 90 - 100 V. The NDPAs were built with six sections in a nonuniform distributed amplifier approach. The small signal gain was ~10 dB over the band with saturated CW output power of 33 - 37 dBm at Vdd = 20 V. The PAE was >35% - 30% up to 6 GHz. The linear NDPAs consist of main and gm3 cells, and show a small signal gain of 6 - 9 dB due to input RF signal routing. The Psat was ~35 dBm at Vdd = 20 V. Based on two-tone testing, the linear NDPA shows improved OIP3 of >50 dBm, compared to OIP3 of 42 dBm of the NDPA without linearization. The resulting OIP3/Pdc is 16:1, which is the highest reported amongst GaN-based distributed amplifiers.