Andreas R. Alt

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.

Fully Passivated AlInN/GaN HEMTs With

We report the fabrication and characterization of 30-nm-gate fully passivated AlInN/GaN high-electron mobility transistors (HEMTs) with cutoff frequencies <i>f</i>_T and <i>f</i>_MAX simultaneously exceeding 200 GHz at a given bias point. The current gain cutoff frequency does not vary significantly for 2.5 <; <i>V</i>_DS <; 10 V, while <i>f</i>_MAX reaches a maximum value of <i>f</i>_MAX = 230 GHz at <i>V</i>_DS = 6 V. This is the first realization of fully passivated AlInN/GaN HEMTs with <i>f</i>_T/<i>f</i>_MAX ≥ 205 GHz, a performance enabled by the careful shaping of the gate electrode profile and the use of a thin 60-nm SiN encapsulation film.

f_{\rm T}/f_{\rm MAX}

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.

of 205/220 GHz

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.

High-Performance 0.1-

We report a new generation of high-performance AlGaN/GaN high-electron-mobility transistors (HEMTs) grown on high-resistivity Si (111) substrates. We map out small- and large-signal device performances against technological parameters such as the gate length and the source-drain contact separation. We report the first large-signal performance for a GaN-on-Si technology offering an output power of 2 W/mm and an associated peak power-added efficiency of 13.8% (peak of 18.5%) at 40 GHz without any field plate. The technology offers measured transconductances of up to 540 mS/mm and cutoff frequencies as high as fT/fMAX = 152/149 GHz at a given bias point. These are the highest cutoff frequencies to date for fully passivated AlGaN/GaN HEMTs on silicon substrates. The results confirm GaN-on-Si technology as a promising contender for low-cost millimeter-wave power electronic applications.

\mu\hbox{m}

Small-signal equivalent circuit (SSEC) models prove indispensable to a broad range of activities, ranging from the understanding of device physics, the analysis of device performance, the characterization and comparison of fabrication processes, the bottom-up construction of large-signal models, the extraction of intrinsic noise parameters, and the design of monolithic microwave integrated circuits (MMICs). Because the SSEC model links the physical structure of the device to its circuit behavior, it allows analysis of the microwave performance as a function of the device geometry. A physically representative model can therefore be used for frequencies extending beyond those of the measurement setup. One must keep in mind that a model is only a physical approximation of a given device, and the more we demand of a model, the more likely we are to expose its various shortcomings. For example, one can stress the limits of a model by extending its frequency range or by applying it to dissimilar technologies; experience shows that with newer material systems, models tend to provide poorer fits to the measured data. In the course of our work, we specifically investigated differences brought about by different materials for devices implemented with a given mask set.

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

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.

150-GHz Cutoff Frequencies and 2-W/mm Output Power at 40 GHz in a Millimeter-Wave AlGaN/GaN HEMT Technology on Silicon

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.

Transistor Modeling: Robust Small-Signal Equivalent Circuit Extraction in Various HEMT Technologies

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.