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The development of InGaAs pseudomorphic high-electron mobility transistors (HEMTs) with state-of-the-art power performance at millimeter-wave frequencies is reported. Results given include maximum power-added efficiencies of 44% at 35 GHz and 36% at 44 GHz, output power of 100 mW with 22% efficiency and 3-dB gain at 60 GHz, and output power of 9 mW at 94 GHz. Preliminary reliability data are presented, and prospects for further improvement in performance-the realization of multifinger HEMTs capable of higher output power and reduction of gate length to 0.1 mu m-are discussed. >

It was observed that the gate breakdown voltage of an unpassivated AlGaAs/GaAs HEMT can move to higher negative values when a current is allowed to flow through the gate under reverse gate bias voltage. When a reverse bias is applied between the gate and source, this breakdown 'walkout' can be accompanied by a permanent increase in device source resistance and decreases in transconductance and drain saturation current. A similar effect was observed in AlGaAs/InGaAs/GaAs pseudomorphic HEMTs and in GaAs MESFETs. This effect was not observed in silicon nitrided passivated devices. >

AlGaAs/InGaAs/GaAs pseudomorphic high electron mobility transistors (HEMT's) with a gate length of 0.1 µm have been successfully fabricated. The HEMT's exhibit a maximum transconductance of 540 mS/mm with excellent pinch-off characteristics. A maximum stable gain (MSG) as high as 18.2 dB was measured at 18 GHz. At 60 GHz the device has demonstrated a minimum noise figure of 2.4 dB with an associated gain of ∼6 dB. These are the best gain and noise results reported to date for HEMT's.

Room-temperature noise performance of high-electron-mobility transistors (HEMTs) has been studied by correlating the microwave/millimeter-wave noise figure with lower frequency model parameters. By comparing devices fabricated from various molecular-beam epitaxially grown wafers, it is found that devices with high transconductance at low drain current generally exhibit superior noise performance. In particular, an optimal noise figure of 1.8 dB has been obtained at 60 GHz with 6.4-dB associated gain for devices from the best wafer. The low thermal noise coefficient ( theta >

AlGaAs/InGaAs/GaAs planar-doped pseudomorphic HEMTs with a gate length of 0.1µm have been successfully fabricated. A maximum extrinsic transconductance g m of 930 mS/mm, corresponding to an intrinsic g m of 1380 mS/mm, is observed in the devices at room temperature. A unity current gain cutoff frequency f T of ∼100 GHz was projected. A maximum gain as high as 19.3 dB was also measured at 18 GHz. At 59 GHz, the devices have demonstrated a minimum noise figure of 2.3 dB with an associated gain of 6.5 dB from one wafer, and 2.5 dB noise figure with 8.0 dB associated gain from another. At 94 GHz, ∼7 dB small signal gain was also measured from a single-stage amplifier. These are the best gain and noise results reported to date for FETs.

Transistor amplification at 94 GHz has been demonstrated for the first time. A single-stage amplifier employing a high-electron-mobility transistor (HEMT) exhibits a small-signal gain of 3.6 dB and an output power of 3.4 mW with 2 dB gain.

The noise performance of 0.25 ?m-gate-length high-electron-mobility transistors at frequencies up to 62 GHz is reported. A room-temperature extrinsic transconductance gm of 480 mS/mm and a maximum frequency of oscillation fmax of 135 GHz are obtained for these transistors. At 30 and 40 GHz the devices exhibit minimum noise figures of 1.5 and 1.8 dB with associated gains of 10.0 and 7.5 dB, respectively. A minimum noise figure as low as 2.7 dB with an associated gain of 3.8 dB has also been measured at 62 GHz. This is the best noise performance ever reported for HEMTs at millimetre-wave frequencies. The results clearly demonstrate the potential of short-gate-length high-electron-mobility transistors for very low-noise applications for frequencies at least up to V-band.