F. Lecourt

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 paper reports on the dc analysis and radio frequency (RF) characterization of a flexible AlGaN/GaN high-electron mobility transistor with a 120-nm gate length. The device provides a maximum dc current density of 470 mA/mm and a peak extrinsic transconductance of 125 mS/mm under flat condition. When the substrate is bent with 0.88% strain, a rise in the 2-DEG density is experimentally observed through the diminution of the on-resistance. This phenomenon is physically attributed to the modification of the piezoelectric field within the barrier under tensile condition. The device also shows a current gain cutoff frequency (Ft) of 32 GHz and a power gain cutoff frequency (Fmax) of 52 GHz. No major variations of RF performance are observed under bending.

High Electron Mobility Heterostructures for High-Power/Frequency Performances

Depletion-mode high-electron mobility transistors (HEMTs) based on a quaternary barrier In0.11Al0.72Ga0.17N/GaN heterostructure on sapphire substrate are fabricated and characterized. This structure shows a very high Hall electron mobility of 2200 cm2/V·s, which is the highest value ever reported on In-containing GaN-based HEMTs. For T-shaped gate transistor with a gate length of 75 nm, current gain (ft) and power gain (fmax) cutoff frequencies of 113 and 200 GHz are extracted from S-parameter measurements, respectively. Nonlinear characterization of a T-shaped gate device with a gate length of 225 nm gives an output power density of 2 W/mm at 40 GHz. These results clearly demonstrate the capabilities of such quaternary barrier-based devices.

Fabrication, Characterization, and Physical Analysis of AlGaN/GaN HEMTs on Flexible Substrates

This paper reports the capability of AlGaN/GaN HEMTs on Si (111) substrates for microwave power applications above 30GHz. A current gain cut-off frequency ft=90GHz and a maximum power gain cut-off frequency fmax=135GHz are obtained for a 80nm gate-length transistor. These results, associated with low lag effects, demonstrate the capability of these transistors for high performance, cost effective, MMIC fabrication on a Si substrate for high frequency microwave power applications.

Power Performance at 40 GHz on Quaternary Barrier InAlGaN/GaN HEMT

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.