E. Delos

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.

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.

Enhancement-mode Al/sub 0.66/In/sub 0.34/As/Ga/sub 0.67/In/sub 0.33/As metamorphic HEMT, modeling and measurements

This paper exhibits experimental and theoretical results on metamorphic high-electron mobility transistor (MM-HEMT). Modeling and measurements provide a better knowledge of device physics which allows us to optimize device structures. We present 10-GHz power performances, pulse and gate measurements, and two-dimensional (2-D) hydrodynamic modeling of enhancement-mode (E-mode) Al/sub 0.66/In/sub 0.34/As/Ga/sub 0.67/In/sub 0.33/As NM-HEMT devices. It is the first time that cap layer thickness has been studied for a MM-HEMT. A typical reverse breakdown voltage of 16 V has been obtained. Gate current issued from impact ionization has been shown, for the first time, in such a device. The 2-D hydrodynamic model is a useful tool for cost engineering because it brings more information in terms of physical quantity distributions, necessary to predict breakdown behavior of FET. The 10-GHz measurements with a load-pull power set-up demonstrate the capabilities for a thick cap device with large gate-to-drain extension since an output power of 140 mW/mm have been obtained which is the state-of-the-art for such a device. These results obtained confirm the great interest of the structures for power application systems. The only work reported, to our knowledge, using a MM-HEMT structure in E-mode with an indium content close to 50% has been studied by Eisenbeiser et al.. Their typical gate-to-drain breakdown voltage was 5.2 V. The 0.6 /spl mu/m /spl times/3 mm devices exhibited 30 mW/mm at 850 MHz.

Enhancement mode metamorphic Al/sub 0.67/In/sub 0.33/As/Ga/sub 0.66/In/sub 0.34/As HEMT on GaAs substrate with high breakdown voltage

This paper presents original and experimental results provided by E-mode Al/sub 0.67/In/sub 0.33/As/Ga/sub 0.66/In/sub 0.34/As metamorphic HEMT. The devices exhibit good dc and rf performances. The 0.4 /spl mu/m gate length devices have saturation current density of 355 mA/mm at +0.6 V gate-to-source voltage. The Schottky characteristic is a typical reverse gate-to-drain breakdown voltage of -16 V. It is the first time, to our knowledge, that gate current issued from impact ionization have been observed in these devices versus gate to drain extension. These results are the first reported for E-mode Al/sub 0.67/In/sub 0.33/As/Ga/sub 0.66/In/sub 0.34/As MM-HEMTs on GaAs substrate.

A 0.15-μm 60-GHz high-power composite channel GaInAs/InP HEMT with low gate current

This letter presents recent improvements and experimental results provided by GaInAs/InP composite channel high electron mobility transistors (HEMT). The devices exhibit good dc and rf performance. The 0.15-/spl mu/m gate length devices have saturation current density of 750 mA/mm at V/sub GS/=+0 V. The Schottky characteristic is a typical reverse gate-to-drain breakdown voltage of -8 V. Gate current issued from impact ionization has been studied in these devices, in the first instance, versus drain extension. At 60 GHz, an output power of 385 mW/mm has been obtained in such a device with a 5.3 dB linear gain and 41% drain efficiency which constitutes the state-of-the-art. These results studied are the first reported for a composite channel Al/sub 0.65/In/sub 0.35/As/Ga/sub 0.47/In/sub 0.53/As/InP HEMT on an InP substrate.

A 60 GHz high power composite channel GaInAs/InP HEMT on InP substrate with L/sub G/=0.15 /spl mu/m

We have improved power performance by studying three different GaInAs/InP composite channel structures. Also, different gate to drain extension devices have been processed. By using composite channel devices, we benefit from the better ionization threshold energy of InP compared to GaInAs (1.69 eV against 0.92 eV). The difference of conduction band offset between the two materials (/spl Delta/E/sub C/=0.2 eV) makes possible electron transfer from GaInAs to InP layers with the same electronic properties. New process technologies have been applied to compare these structures. The gate current resulting from the impact ionization phenomena is reduced to 30 /spl mu/A at V/sub DS/=4.5 V for a large extension device, which constitute the best result among the three structures. Also, we improve power performances at 60 GHz by reducing the GaInAs channel width and substituting delta doping by bulk doping. The best device performance is 422 mW/mm at V/sub DS/=3 V and V/sub GS/=0.7 V.