Hansruedi Benedickter

205-GHz (Al,In)N/GaN HEMTs

We report 55-nm gate AlInN/GaN high-electron-mobility transistors (HEMTs) featuring a short-circuit current gain cutoff frequency of fT = 205 GHz at room temperature, a new record for GaN-based HEMTs. The devices source a maximum current density of 2.3 A/mm at VGS = 0 V and show a measured transconductance of 575 mS/mm, which is the highest value reported to date for nonrecessed gate nitride HEMTs. Comparison to state-of-the-art thin-barrier AlGaN/GaN HEMTs suggests that AlInN/GaN devices benefit from an advantageous channel velocity under high-field transport conditions.

Comparison of the Radiation Efficiency for the Dielectric Resonator Antenna and the Microstrip Antenna at Ka Band

The radiation efficiency of a dielectric resonator antenna (DRA) and a microstrip antenna (MSA) at Ka band is investigated numerically and experimentally. For direct comparison, one cylindrical DRA and one circular disk MSA were designed with similar feeding networks for operation at around 35 GHz. The efficiency of both devices was measured using the directivity/gain (D/G) method and the Wheeler cap method, in both of which the losses in the test system and the feeding structure were taken into account for calibration purposes. A good agreement between measured and simulated results for both methods is found, when considering the effect of the sampling interval and cross-polarization in the D/G method and the effect of the metallic cap size in the Wheeler cap method. It is finally demonstrated that the radiation efficiency of the DRA is significantly higher than that of the MSA at millimeter wave frequencies.

High-Performance 0.1-

The realization of high-performance 0.1-mum gate AlGaN/GaN high-electron mobility transistors (HEMTs) grown on high-resistivity silicon substrates is reported. Our devices feature cutoff frequencies as high as fT = 75 GHz and fMAX = 125 GHz, the highest values reported so far for AlGaN/GaN HEMTs on silicon. The microwave noise performance is competitive with results achieved on other substrate types, such as sapphire and silicon carbide, with a noise figure F = 1.2-1.3 dB and an associated gain Gass = 8.0-9.5 dB at 20 GHz. This performance demonstrates that GaN-on-silicon technology is a viable alternative for low-cost millimeter-wave applications.

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Grown on a (111) high-resistivity silicon substrate, 0.1-mum gate AlInN/GaN high-electron mobility transistors (HEMTs) achieve a maximum current density of 1.3 A/mm, an extrinsic transconductance of 330 mS/mm, and a peak current gain cutoff frequency as high as fT = 102 GHz, which is the highest value reported so far for nitride-based devices on silicon substrates, as well as for any AlInN/GaN-based HEMT regardless of substrate type. Continuous-wave power measurements in class-A operation at 10 GHz with VDS = 15 V revealed a 19-dB linear gain, a maximum output power density of 2.5 W/mm with an ~23% power-added efficiency (PAE), and a 9-dB large-signal gain. At VDS = 8 V, the output power is 1 W/mm, and the peak PAE reaches 50%. Results demonstrate the interest of AlInN/GaN on silicon HEMT technology for low-cost millimeter-wave and high-power applications.

Gate AlGaN/GaN HEMTs on Silicon With Low-Noise Figure at 20 GHz

We report high-speed fully passivated deep submicrometer (Al,Ga)N/GaN high-electron mobility transistors (HEMTs) grown on (111) high-resistivity silicon with current gain cutoff frequencies of as high as fT = 107 GHz and maximum oscillation frequencies reaching fMAX = 150 GHz. Together, these are the highest fT and fMAX values achieved for GaN-based HEMTs implemented on silicon substrates to date. The performance reported here is competitive with recently published results for similar geometry high-performance passivated HEMTs on semi-insulating silicon-carbide substrates.

102-GHz AlInN/GaN HEMTs on Silicon With 2.5-W/mm Output Power at 10 GHz

[1] We present a method for extracting spatially resolved water content profiles θ(x) from a two-wire time domain reflectometry (TDR) probe. The profile θ(x) is represented in terms of the dielectric e r (x) and ohmic σ(x)properties in the longitudinal direction of the TDR probe. We solve the inverse problem iteratively by combining a one-dimensional time domain solution of the transmission line equations and a genetic optimization method. The method is capable of finding the global optimum in a complicated error landscape without initial assumptions, except physically reasonable limits. The method utilizes both the position and the magnitude of the TDR signal. We analyze water content profiles from laboratory measurements and demonstrate that the achievable spatial resolution can be made as low as 2 cm and even smaller. The present implementation of the numerical code demonstrates the practical feasibility of spatially resolved water content profiles.

107-GHz (Al,Ga)N/GaN HEMTs on Silicon With Improved Maximum Oscillation Frequencies

We report on ultrahigh-speed 80 nm AlInN/GaN high-electron-mobility transistors (HEMTs) grown on (111) high-resistivity silicon substrates. The devices feature a peak measured transconductance gM = 415 mS/mm, a maximum current of 1.43 A/mm with a ratio ION/IOFF > 106, and current gain and maximum oscillation cutoff frequencies of fT = 143 GHz and fMAX = 176 GHz, which are the highest cutoff frequencies ever achieved for any GaN HEMTs on silicon substrates. The results demonstrate the outstanding potential of AlInN/GaN HEMTs grown on silicon for low-cost high-performance millimeter-wave electronics.

Spatially resolved water content profiles from inverted time domain reflectometry signals

One-hundred-nanometer-gate (Al,In)N/GaN high-electron-mobility transistors (HEMTs) grown on semi-insulating SiC achieve a maximum current density of 1.84 A/mm at VGS = 0 V, an extrinsic transconductance of 480 mS/mm, and a peak current gain cutoff frequency as high as fT = 144 GHz, which is the highest so far reported for any (Al,In)N/GaN-based HEMT. This fT matches the best published values that we could find for 100-nm-gate (Al,Ga)N/GaN HEMTs, thus closing the cutoff frequency gap between (Al,In)N/GaN and (Al,Ga)N/GaN HEMTs. Additionally, similar devices grown on (111) high-resistivity silicon show a peak fT of 113 GHz, also setting a new performance benchmark for (Al,In)N/GaN HEMTs on silicon. Our findings indicate significant performance advantages for (Al,In)N/GaN HEMTs fabricated on SiC substrates. The improved performance for devices grown on SiC is derived from the superior transport properties of (Al,In)N/GaN 2DEGs grown on that substrate.

Ultrahigh-Speed AlInN/GaN High Electron Mobility Transistors Grown on (111) High-Resistivity Silicon with FT = 143 GHz

We developed an efficient method to extract a large-signal lookup table model for InP high electron-mobility transistors that takes impact ionization into account. By measuring the device on a logarithmic frequency scale, we obtain high resolution at lower frequencies to accurately characterize impact ionization, and a sufficient number of data points at millimeter-wave frequencies to extract the nonquasi-static parameters. Model validation through linear and nonlinear device measurements and its application to monolithic-microwave integrated-circuit design are presented.

100-nm-Gate (Al,In)N/GaN HEMTs Grown on SiC With

We report the realization of 0.3-μm emitter InP/GaAsSb/InP DHBTs with cutoff frequencies <i>f</i>_T = 365 GHz and <i>f</i>_MAX = 501 GHz. Our devices were implemented with a 15-nm C-doped graded base and a 125-nm InP collector and feature a peak current gain β = 35, with a base sheet resistance <i>R</i>_SH = 1160 Ω/sq. The present transistors are the first InP/GaAsSb DHBTs to feature <i>f</i>_MAX = 500 GHz, according to three extraction schemes. The present transistor performance is limited by an undepleted collector layer associated with a doping tail extending from the subcollector.