E. Okada

Power Performance at 40 GHz of AlGaN/GaN High-Electron Mobility Transistors Grown by Molecular Beam Epitaxy on Si(111) Substrate

This letter reports on the demonstration of microwave power performance at 40 GHz on AlGaN/GaN high-electron mobility transistor grown on silicon (111) substrate by molecular beam epitaxy. A maximum dc current density of 1.1 A· mm-1 and a peak extrinsic transconductance of 374 mS · mm-1 are obtained for 75-nm gate length device. At VDS = 25 V, continuous-wave output power density of 2.7 W · mm-1 is achieved at 40 GHz associated with 12.5% power-added efficiency and a linear power gain (G p) of 6.5 dB. The device exhibits an intrinsic current gain cutoff frequency FT of 116 GHz and a maximum oscillation frequency FMAX of 150 GHz. This performance demonstrates the capability of low cost microwave power devices up to Ka-band.

Optimization of

In this paper, we propose to optimize Al0.29Ga0.71N/GaN heterostructures on silicon substrate to obtain high electron mobility transistors featuring high-power/frequency performances. The polarization electric fields are engineered by varying the layer thicknesses of the cap and the barrier, and by changing the type of buffer (GaN or AlGaN). The aim of this paper is to find the best tradeoff between the active layer thickness reduction and the achievement of a reasonable drain current to satisfy the requirements for high performances. The optimum heterostructure device presents an output power density of 1.5 W/mm at 40 GHz, among the best reported on silicon substrate.

{\rm Al}_{0.29}{\rm Ga}_{0.71}{\rm N}/{\rm GaN}

This letter reports on the first demonstration of microwave power performance at 10 GHz on flexible AlGaN/GaN high-electron-mobility transistor (HEMT). A maximum dc current density of 620 mA/mm at VGS = 0 V and a peak extrinsic transconductance of 293 mS/mm are obtained for a 2 × 50 × 0.1 μm2 flexible device. At VDS = 5 V, a continuous-wave saturation output power density of 0.42 W/mm is achieved at 10 GHz, and associated with a maximum power-added efficiency of 29.8% and a linear power gain of 15.8 dB. The device exhibits an intrinsic current gain cutoff frequency FT of 38 GHz and a maximum oscillation frequency FMAX of 75 GHz. This result demonstrates the capability of flexible GaN-based HEMT for the development of applications requiring mechanical flexibility, high frequency operation, as well as high power performance.

High Electron Mobility Heterostructures for High-Power/Frequency Performances

We report on AlN/GaN double heterostructures for high frequency applications. 600 hours preliminary reliability assessment has been performed on these emerging RF devices, showing promising millimeter-wave 100 nm gate length GaN-on-Si device stability for the first time. A 150 nm AlN/GaN double heterostructure has been developed and evaluated on SiC substrate. State-of-the-art CW power-added-efficiencies (PAE) at 10 and 18 GHz have been achieved on ultrathin barrier (6 nm) GaN devices while operating at a drain bias exceeding 30 V.

First Power Performance Demonstration of Flexible AlGaN/GaN High Electron Mobility Transistor

We report a 94-GHz large-signal load-pull characterization of InP/GaAsSb double heterojunction bipolar transistors. The investigated devices have an emitter area of 0.20 × 9.5 μm². Biased for highest power added efficiency (PAE), an output power of 6.62 mW/μm² (11 dBm), a power gain of 5.2 dB, and a PAE of 27.7% have been obtained. Biased for highest output power, 10.26 mW/μm² (12.8 dBm) has been achieved without significant degradation of the PAE (25.2%) and the power gain (4.5 dB).

High performance high reliability AlN/GaN DHFET

We report on a comparison of the ultrathin (sub-10 nm barrier thickness) AlN/GaN heterostructure using two types of buffer layers: 1) carbon doped GaN high electron mobility transistors (HEMTs) and 2) double heterostructure field effect transistor (DHFET). It is observed that the carbon doped HEMT structure shows better electrical characteristics, with a maximum drain current density Id of 1.3 A/mm, a transconductance Gm of 500 mS/mm and a maximum oscillation frequency fmax of 234 GHz while using a gate length of 220 nm. The low trapping effects together with high frequency performance and excellent electron confinement under high bias enabled to achieve a state-of-the-art combination at 18 GHz of output power density (Pout > 6 W/mm) and power added efficiency (PAE) close to 40% at Vds as high as 30V. At 40 GHz, a PAE above 35% is still observed in spite of the rather large gate length. A key feature is the low gate leakage current of only few tenths of μA/mm that remains stable after many load-pull sweeps at various frequency in the case of carbon doped HEMT, which is attributed to a significant reduction of the self-heating as compared to the DHFET.

0.2-

Stressed gallium nitride micro-resonators with integrated piezoelectric transducers have been designed, fabricated, and characterized. In resonant beams, it is well known that tensile stress can be used to increase the resonant frequency. Here we additionally calculate the modification of the mode shape functions of out-of-plane flexural modes. We derive an analytical model to predict both the resonant frequency and the piezoelectric actuation factor of our resonators. We show that a good agreement can be obtained and that the actuator must be properly designed to optimize the electromechanical transduction.

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The aim of this paper is to optimize the epitaxial layer structure of an AlGaN/GaN high electron mobility transistor (HEMT) for high power density at high frequency. The idea is to play on the polarization engineering with the different layers of the epitaxial stack. The influence of the cap and barrier layer thicknesses, the aluminum content in the barrier and the insertion of an AlGaN buffer layer are studied through the electron gas density, electron mobility and sheet resistance. This permits to find out the best trade-off in order to satisfy the requirements for high performances.