J.-C. Gerbedoen

Power Performance of AlGaN/GaN High-Electron-Mobility Transistors on (110) Silicon Substrate at 40 GHz

This letter reports the first millimeter-wave power demonstration of AlGaN/GaN high-electron-mobility transistors grown on a (110) silicon substrate. Owing to an AlN/AlGaN stress-mitigating stack and in spite of the twofold surface symmetry of Si (110), it is possible to obtain crack-free GaN layers for the fabrication of millimeter-wave power devices with high performance. The device exhibits a maximum dc drain current density of 1.55 A/mm at VGS = 0 V with an extrinsic transconductance of 476 mS/mm. An extrinsic current gain cutoff frequency of 81 GHz and a maximum oscillation frequency of 106 GHz are deduced from Sij parameters. At 40 GHz, an output power density of 3.3 W/mm associated with a power-added efficiency of 20.1% and a linear power gain of 10.6 dB is obtained.

AlGaN/GaN HEMTs on (001) Silicon Substrate With Power Density Performance of 2.9 W/mm at 10 GHz

AlGaN/GaN High Electron Mobility Transistors (HEMT) on a (001)-oriented silicon (Si) substrate are fabricated. The device with a gate length of 300 nm and a total gate periphery of 300 μm exhibits a maximum dc drain current density of 600 mA/mm at VGS = 0 V with an extrinsic transconductance (gm) of about 200 mS/mm. An extrinsic current gain cutoff frequency (ft) of 37 GHz and a maximum oscillation frequency (fmax) of 55 GHz are deduced from S-parameter measurements. At 10 GHz, an output power density of 2.9 W/mm associated to a power-added efficiency (PAE) of 20% and a linear gain of 7 dB are obtained at VDS = 30 V and VGS = -2 V. To our knowledge, these power results represent the highest output power density ever reported at this frequency on GaN HEMT grown on (001) Si substrate.

Diamond and Cubic Boron Nitride: Properties, Growth and Applications

Since their first synthesis, cubic boron nitride (c‐BN) and diamond thin films have triggered a vivid interest in these wide band gap materials for many different applications. Because of superior properties, c‐BN and diamond can be applied in optic, electronic and acoustic for high performances devices. In this discussion, we first describe briefly the properties of c‐BN and diamond and we review both the growth techniques and the progresses achieved in the synthesis of c‐BN and diamond, and in a second part, characteristics of new c‐BN and diamond UV detectors for solar observation are reported. These photo‐detectors present extremely low dark current, high breakdown voltage, high responsivity and stability under UV irradiation. Finally, diamond based acoustic devices and sensors are presented. High frequency acoustic wave devices can be design for high frequency filtering or sensing applications. Diamond/AlN micro‐cantilevers are excellent platform for sensor applications.

Dispersion properties and low infrared optical losses in epitaxial AlN on sapphire substrate in the visible and infrared range

Optical waveguiding properties of a thick wurtzite aluminum nitride highly [002]-textured hetero-epitaxial film on (001) basal plane of sapphire substrate are studied. The physical properties of the film are determined by X-ray diffraction, atomic force microscopy, microRaman, and photocurrent spectroscopy. The refractive index and the thermo-optic coefficients are determined by m-lines spectroscopy using the classical prism coupling technique. The optical losses of this planar waveguide are also measured in the spectral range of 450-1553 nm. The lower value of optical losses is equal to 0.7 dB/cm at 1553 nm. The optical losses due to the surface scattering are simulated showing that the contribution is the most significant at near infrared wavelength range, whereas the optical losses are due to volume scattering and material absorption in the visible range. The good physical properties and the low optical losses obtained from this planar waveguide are encouraging to achieve a wide bandgap optical guiding platform from these aluminum nitride thin films.

Performance of Unstuck - Gate AlGaN/GaN HEMTs on (001) Silicon Substrate at 10 GHz

This paper shows the capability of AlGaN/GaN high electron mobility transistors (HEMTs) on (001) oriented silicon substrate with 300 nm gate length using unstuck Gamma gate for low cost device microwave power applications. The total gate periphery of 300 mum, exhibits a maximum DC drain current density of 600 mA/mm at VDS=7V with an extrinsic transconductance (gm max) around 200 mS/mm. An extrinsic current gain cutoff frequency (fT) of 37 GHz and a maximum oscillation frequency (fmax) of 55 GHz are deduced from Sij-parameters measurements. At 10 GHz, an output power density of 2.9 W/mm associated to a power added efficiency (PAE) of 20% and a linear gain of 7 dB are obtained at VDS=30 V and VGS=-2 V.