M.A. Thompson

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%. >

AlInAs-GaInAs HEMTs utilizing low-temperature AlInAs buffers grown by MBE

Low-temperature AlInAs buffer layers incorporated in AlInAs-GaInAs HEMT epitaxial layers grown by MBE are discussed. A growth temperature of 150 degrees C followed by a short anneal is shown to eliminate kinks in the device I-V characteristic and sidegating and to reduce the output conductance dramatically.<<ETX>>

650-AA self-aligned-gate pseudomorphic Al/sub 0.48/In/sub 0.52/As/Ga/sub 0.2/In/sub 0.8/As high electron mobility transistors

The authors report on the design and fabrication of a 650-AA self-aligned-gate pseudomorphic Al/sub 0.48/In/sub 0.52/As/Ga/sub 0.2/In/sub 0.8/As high electron mobility transistor (HEMT) with a state-of-the-art current gain cutoff frequency of over 300 GHz. This work clearly demonstrates the potential of sub-0.1- mu m gate-length HEMTs for near-future microwave and millimeter-wave applications.<<ETX>>

Ultra-high-speed digital circuit performance in 0.2- mu m gate-length AlInAs/GaInAs HEMT technology

The fabrication of fifteen-stage ring oscillators and static flip-flop frequency dividers with 0.2- mu m gate-length AlInAs/GaInAs HEMT technology is described. The fabricated HEMT devices within the circuits demonstrated a g/sub m/ transconductance of 750 mS/mm and a full-channel current of 850 mA/mm. The measured cutoff frequency of the device is 120 GHz. The shortest gate delay measured for buffered-FET-logic (BFL) ring oscillators at 300 K was 9.3 ps at 66.7 mW/gate (fan-out=1); fan-out sensitivity was 1.5 ps per fanout. The shortest gate delay measured for capacitively enhanced logic (CEL) ring oscillators at 300 K was 6.0 ps at 23.8 mW/gate (fan-out=1) with a fan-out sensitivity of 2.7 ps per fan-out. The CEL gate delay reduced to less than 5.0 ps with 11.35-mW power dissipation when measured at 77 K. The highest operating frequency for the static dividers was 26.7 GHz at 73.1 mW and 300 K.<<ETX>>

Novel high performance self-aligned 0.15 micron long T-gate AlInAs-GaInAs HEMTs

A novel self-aligned technique for 0.15- mu m-gate-length HEMTs (high electron mobility transistors) has been demonstrated. This technology uses a 0.15- mu m-long T-gate structure defined by e-beam lithography with a SiO/sub 2/ sidewall to implement the self-aligned scheme. The resultant device has low source and drain resistances, low gate resistance (200 Omega /mm), and a passivating layer over the active channel. Devices with an oxide sidewall yielded an f/sub T/ of 177 GHz, whereas devices with no sidewall exhibited an f/sub T/ greater than 250 GHz. The difference has been related to process damage during plasma deposition of SiO/sub 2/.<<ETX>>

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. >

High-power V-band AlInAs/GaInAs on InP HEMTs

The DC and RF performance of delta -doped channel AlInAs/GaInAs on InP power high-electron-mobility transistors (HEMTs) are reported. A 450- mu m-wide device with a gate-length of 0.22 mu m has achieved an output power of 150 mW (at the 1-dB gain compression point) with power-added efficiency of 20% at 57 GHz. The device has a saturated output power of 200 mW with power-added efficiency of 17%. This is the highest output power measured from a single InP-based HEMT at this frequency, and demonstrates the feasibility of these HEMTs for high-power applications in addition to low-noise applications at V-band.<<ETX>>

Very low noise and low power operation of cryogenic AlInAs/GaInAs/InP HFET's

The cryogenic performance of 0.15 /spl mu/m gate length AlInAs/GaInAs/InP devices is reported. A noise temperature of less than 10 K (less than five times over quantum limit hf/k) is demonstrated at 40 GHz with a power consumption of less than 0.6 mW under optimal noise bias condition. With about 5 K penalty in noise performance at 40 GHz, the devices could be operated with as little as 60 /spl mu/W total power consumption. An interpretation of the measured noise performance with the help of a noise model, room temperature S-parameters and DC characteristics (measured at room and cryogenic temperatures) is offered.<<ETX>>

High-efficiency GaAs-based pHEMT C-band power amplifier

A high-efficiency C-Band power amplifier design utilizing AIGaAs/InGaAs/GaAs pHEMTs is reported. On-wafer active loadpull power measurements at 4.5 GHz of a 0.25μm x 1.2 mm pHEMT exhibited an output power of 0.35 W and power-added efficiency of 79%. A singlestage MIC amplifier fabricated with a 2.8-mm-wide pHEMT resulted in P/sub out/ = 1.2 W and PAE = 74% at 4 GHz. These results demonstrate the potential of pHEMTs to significantly improve the efficiency performance of microwave solid state power amplifiers compared to present MESFET designs.