V. Hoel

Output power density of 5.1/mm at 18 GHz with an AlGaN/GaN HEMT on Si substrate

Microwave frequency capabilities of AlGaN/GaN high electron mobility transistors (HEMTs) on high resistive silicon (111) substrate for power applications are demonstrated in this letter. A maximum dc current density of 1 A/mm and an extrinsic current gain cutoff frequency (F/sub T/) of 50 GHz are achieved for a 0.25 /spl mu/m gate length device. Pulsed and large signal measurements show the good quality of the epilayer and the device processing. The trapping phenomena are minimized and consequently an output power density of 5.1 W/mm is reached at 18 GHz on a 2/spl times/50/spl times/0.25 /spl mu/m/sup 2/ HEMT with a power gain of 9.1dB.

Improved Monte Carlo algorithm for the simulation of /spl delta/-doped AlInAs/GaInAs HEMTs

A classical Monte Carlo (MC) device simulation has been modified to locally introduce the effects of electron degeneracy and nonequilibrium screening. Its validity in the case of AlInAs/GaInAs HEMTs has been checked through the comparison, first, with a quantum Schrodinger-Poisson (SP) simulation in the case of a complicated layer structure, which is actually used in the fabrication of real devices, and second, with experimental results of static characteristics of recessed /spl delta/-doped HEMTs.

Metamorphic In/sub 0.4/Al/sub 0.6/As/In/sub 0.4/Ga/sub 0.6/As HEMTs on GaAs substrate

New In/sub 0.4/Al/sub 0.6/As/In/sub 0.4/Ga/sub 0.6/As metamorphic (MM) high electron mobility transistors (HEMTs) have been successfully fabricated on GaAs substrate with T-shaped gate lengths varying from 0.1 to 0.25 /spl mu/m. The Schottky characteristics are a forward turn-on voltage of 0.7 V and a gate breakdown voltage of -10.5 V. These new MM-HEMTs exhibit typical drain currents of 600 mA/mm and extrinsic transconductance superior to 720 mS/mm. An extrinsic current cutoff frequency f/sub T/ of 195 GHz is achieved with the 0.1-/spl mu/m gate length device. These results are the first reported for In/sub 0.4/Al/sub 0.6/As/In/sub 0.4/Ga/sub 0.6/As MM-HEMTs on GaAs substrate.

AlGaN-GaN HEMTs on Si with power density performance of 1.9 W/mm at 10 GHz

AlGaN-GaN high electron mobility transistors (HEMTs) on silicon substrate are fabricated. The device with a gate length of 0.3-/spl mu/m and a total gate periphery of 300 /spl mu/m, exhibits a maximum drain current density of 925 mA/mm at V/sub GS/=0 V and V/sub DS/=5 V with an extrinsic transconductance (g/sub m/) of about 250 mS/mm. At 10 GHz, an output power density of 1.9 W/mm associated to a power-added efficiency of 18% and a linear gain of 16 dB are achieved at a drain bias of 30 V. To our knowledge, these power results represent the highest output power density ever reported at this frequency on GaN HEMT grown on silicon substrates.

Effect of the T-gate on the performance of recessed HEMTs. A Monte Carlo analysis

A microscopic study of 0.1 µm recessed gate -doped AlInAs/GaInAs HEMTs has been performed by using a semiclassical Monte Carlo device simulation. The geometry and layer structure of the simulated HEMT is completely realistic, including recessed gate and -doping configuration. The usual T-gate technology is used to improve the device characteristics by reducing the gate resistance. For first time we take into account in the Monte Carlo simulations the effect of the T-gate and the dielectric used to passivate the device surface, which affects considerably the electric field distribution inside the device. The measured Id-Vds characteristics of a real device are favourably compared with the simulation results. When comparing the complete simulation with the case in which Poisson equation is solved only inside the semiconductor, we find that even if the static I-V characteristics remain practically unchanged, important differences appear in the dynamic and noise behaviour, reflecting the influence of an additional capacitance.

High microwave and noise performance of 0.17-/spl mu/m AlGaN-GaN HEMTs on high-resistivity silicon substrates

AlGaN-GaN high-electron mobility transistors (HEMTs) based on high-resistivity silicon substrate with a 0.17-/spl mu/m T-shape gate length are fabricated. The device exhibits a high drain current density of 550 mA/mm at V/sub GS/=1 V and V/sub DS/=10 V with an intrinsic transconductance (g/sub m/) of 215 mS/mm. A unity current gain cutoff frequency (f/sub t/) of 46 GHz and a maximum oscillation frequency (f/sub max/) of 92 GHz are measured at V/sub DS/=10 V and I/sub DS/=171 mA/mm. The radio-frequency microwave noise performance of the device is obtained at 10 GHz for different drain currents. At V/sub DS/=10 V and I/sub DS/=92 mA/mm, the device exhibits a minimum-noise figure (NF/sub min/) of 1.1 dB and an associated gain (G/sub ass/) of 12 dB. To our knowledge, these results are the best f/sub t/, f/sub max/ and microwave noise performance ever reported on GaN HEMT grown on Silicon substrate.

The indium content in metamorphic As/As HEMTs on GaAs substrate: a new structure parameter

Abstract State-of-the art metamorphic In x Al 1−x As/ In x Ga 1−x As HEMTs (MM-HEMTs) on a GaAs substrate with different indium compositions x=0.33 , 0.4 and 0.5 have been realized and characterized. The gate lengths Lg are 0.1 and 0.25 μm. These devices have been compared with lattice matched HEMTs on an InP substrate. DC-characteristics of 0.1 μm gate length MM-HEMTs show drain-to-source current Ids of the order of 550–650 mA/mm, and extrinsic transconductance of about 800 mS/mm. Schottky characteristics exhibit a gate reverse breakdown voltage varying from −14 to −7 V for x=0.33 –0.5, with an intermediate value of −10.5 V for x=0.4 . A small signal equivalent circuit of our 0.1 μm MM-HEMTs give intrinsic transconductance higher than 1100 mS/mm, with similar values of 1350 and 1450 mS/mm for x=0.5 and the lattice matched HEMT, respectively. The MM-HEMTs with a gate length of 0.25 μm present a cutoff frequency fT close to 100 GHz. To achieve the same result with pseudomorphic HEMTs on GaAs, a smaller gate length has to be realized, which requires the use of an electron beam lithography and therefore increases the device costs. For L g =0.1 μm, fT reaches 160, 195 and 180 GHz for x=0.33 , 0.4 and 0.5, respectively. These values are close to f T =210 GHz obtained for a lattice matched HEMTs on InP realized with the same technological process. The MM-HEMTs are therefore good alternatives to PM-HEMTs on GaAs and LM-HEMTs on InP in the V bands and W bands while maintaining a GaAs substrate. Moreover, metamorphic In0.4Al0.6As/In0.4Ga0.6As HEMTs exhibit a comparable microwave performance with large voltage operation than the MM-HEMT with a 0.5 indium content and the lattice matched HEMTs. These results indicate that a device with indium content x=0.4 is particularly attractive for the realization of low-noise and power circuits on the same wafer.

MBE growth of AlGaN/GaN HEMTS on resistive Si(111) substrate with RF small signal and power performances

In this paper, we report on the properties of GaN films and AlGaN/GaN HEMT structures grown by molecular beam epitaxy on resistive Si(1 1 1) substrates. The properties of the GaN buffer layer and the AlGaN/GaN HEMTs are presented. Finally, both static and high-frequency performances of sub-micron gate length devices are analyzed demonstrating their RF power capability

InAlN/GaN HEMTs on Sapphire Substrate With 2.9-W/mm Output Power Density at 18 GHz

In this letter, small- and large-signal measurements of an In_0.15Al_0.82N/AlN/GaN high-electron-mobility transistor (HEMT) grown on a sapphire substrate with a 225-nm T-shaped gate are described. A maximum dc current density of 1.2 A/mm and a peak extrinsic transconductance of 460 mS/mm are obtained. The device exhibits a current gain cutoff frequency (<i>F</i>_T) and a power gain cutoff frequency (<i>F</i>_MAX) of 52 and 120 GHz, respectively. At <i>V</i>_DS = 15 V, a continuous-wave output power density of 2.9 W/mm was achieved at 18 GHz with an associated power-added efficiency of 28% and a power gain of 15 dB. It is the best value ever reported from InAlN/GaN HEMTs grown on a sapphire substrate.

AlGaN/GaN HEMT High Power Densities on

In this letter, successful operation at 10 GHz of T-gate HEMTs on epitaxial structures grown by metal-organic chemical vapor deposition (MOCVD) or MBE on composite substrates is demonstrated. The used device fabrication process is very similar to the process used on monocrystalline SiC substrate. High power density was measured on both epimaterials at 10 GHz. The best value is an output power density of 5.06 W/mm associated to a power-added efficiency (PAE) of 34.7% and a linear gain of 11.8 dB at VDS = 30 V for the components based on MOCVD-grown material. The output power density is 3.58 W/mm with a maximum PAE of 25% and a linear gain around 15 dB at VDS = 40 V for the MBE-grown material.