Loi D. Nguyen

50-nm self-aligned-gate pseudomorphic AlInAs/GaInAs high electron mobility transistors

The design and fabrication of a class of 50-nm self-aligned-gate pseudomorphic AlInAs/GaInAs high electron mobility transistors (HEMTs) with potential for ultra-high-frequency and ultra-low-noise applications are reported. These devices exhibit an extrinsic transconductance of 1740 mS/mm and an extrinsic current-gain cutoff frequency of 340 GHz at room temperature. The small-signal characteristics of a pseudomorphic and a lattice-matched AlInAs/GaInAs HEMT with similar gate length (50 nm) and gate-to-channel separation (17.5 nm) are compared. The former demonstrates a 16% higher transconductance and a 15% higher current-gain cutoff frequency, but exhibits a 38% poorer output conductance. An analysis of the high-field transport properties of ultra-short gate-length AlInAs/GaInAs HEMTs shows that a reduction of gate length from 150 to 50 nm neither enhances nor reduces their average velocity. In contrast, the addition of indium from 53% to 80% improves this parameter by 19%. >

155- and 213-GHz AlInAs/GaInAs/InP HEMT MMIC oscillators

We report on the design and measurement of monolithic 155- and 213-GHz quasi-optical oscillators using AlInAs/GaInAs/InP HEMTs. These results are believed to be the highest frequency three-terminal oscillators reported to date. The indium concentration in the channel was 80% for high sheet charge and mobility. The HEMT gates were fabricated with self-aligned sub-tenth-micrometer electron-beam techniques to achieve gate lengths on the order of 50 nm and drain-source spacing of 0.25 /spl mu/m. Planar antennas were integrated into the fabrication process resulting in a compact and efficient quasioptical Monolithic Millimeter-wave Integrated Circuit (MMIC) oscillator. >

V-band high-efficiency high-power AlInAs/GaInAs/InP HEMT's

The authors report on the state-of-the-art power performance of InP-based HEMTs (high electron mobility transistors) at 59 GHz. Using a 448- mu m-wide HEMT with a gate length of 0.15 mu m, an output power of 155 mW with a 4.9-dB gain and a power-added efficiency of 30.1% were obtained. By power-combining two of these HEMTs, an output power of 288 mW with 3.6-dB gain and a power-added efficiency of 20.4% were achieved. This is the highest output power reported with such a high efficiency for InP-based HEMTs, and is comparable to the best results reported for AlGaAs/InGaAs on GaAs pseudomorphic HEMTs at this frequency. >

Millimeter-wave waveguide-bandwidth cryogenically-coolable InP HEMT amplifiers

The design, construction and performance of 65-90 GHz and 75-110 GHz low-noise cryogenically-coolable amplifiers are presented. A comparison between modeled and measured performance is shown. A laboratory receiver exhibiting an average noise of 50 K across 65-90 GHz and 70 K across 75-110 GHz is described. These are the widest band and lowest noise HEMT receivers ever reported at these frequencies.

Millimeter wave InP HEMT technology: Performance and applications

Abstract This paper describes the performance, reliability, and applications of a new millimeterwave technology: the indium phosphide high electron mobility transistor (InP HEMT). This advanced technology is potentially an enabling technology for a wide range of millimeterwave systems.

Ka-band InP high electron mobility transistor monolithic microwave integrated circuit reliability

Abstract The reliability of AlInAs/GaInAs high electron mobility transistor (HEMT) monolithic microwave integrated circuits on InP substrates from HRL Labs has been studied with elevated-temperature lifetests on Ka-band LNAs, as well as ramped-voltage tests on individual capacitors. In the lifetests the LNAs were put under normal DC bias, and aging was accelerated by heating to channel temperatures of 190°C and 210°C. Room-temperature characterizations involved DC tests of HEMT parameters as well as 30 GHz measurements of gain, noise figure and phase. Aging caused the noise figure to drop by a few tenths of a dB, and the phase changed by ±10°. The gain dropped gradually by several dB. Taking 1 dB drop in gain as the failure criterion, we find an activation energy of 1.1 eV, and a mean time to failure (MTTF) at an operating channel temperature of 70°C of 7×106 h. In the ramped-voltage tests, 10×10 μm 2 capacitors were taken to breakdown at two different temperatures, and several ramp rates. This yielded a voltage acceleration factor of γ=36–39 nm/V, and thermal activation energy of 0.11–0.13 eV. Next, ramped voltage tests were conducted on 200×200 μm 2 capacitors, typical of those in circuits. These were done at 25°C and 3.0 V/s only, and at least 1000 specimens were tested per wafer. The known acceleration factors were used to find the MTTFs at 70°C, with operating biases of 5 or 10 V. For the majority of the population the MTTFs are about 109 h, while only 0.07% of the population has MTTF less than 1×106 h. The combination of results from elevated-temperature lifetests and ramped-voltage capacitor tests indicates excellent reliability for this MMIC technology in terms of known “wearout” failure mechanisms.

Coplanar waveguide InP-based HEMT MMICs for microwave and millimeter wave applications

We have developed and fabricated a variety of single-stage coplanar waveguide MMIC amplifiers based on our InP-based AlInAs/GaInAs HEMT device technology. The measured f(t) of 0.15-micron devices was 120 GHz and fmax was 200 GHz. The dc transconductance was greater than 720 mS/mm. The 12-GHz single-stage MMIC amplifier had a noise figure of 1.3 dB with an associated gain of 16.0 dB. A 35 GHz single-stage amplifier had a measured gain of 10.9 dB and a measured input return loss of -14.4 dB. A 60 GHz single-stage amplifier had a measured gain of 8.4 dB and a measured input return loss of -18.4 dB.

Room temperature and cryogenic performance of self-aligned AlInAs-GaInAs HEMTs with 0.15-um gate length

A novel self-aligned technique for 0.15 ?m gate length AlInAs-GalnAs HEMTs has been demonstrated. Devices with an oxide sidewall yielded an fT of 177 GHz whereas devices with no sidewall exhibited an fT greater than 250 GHz.nThe difference has been related to process damage during plasma deposition of SiO2. An extrinsic fT of 292 GHz was measured at 77K.