L.M. Jelloian

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%. >

High-performance submicrometer AlInAs-GaInAs HEMT's

The performance of long (1.3- mu m) and short (0.3- mu m) gate-length Al/sub 0.48/In/sub 0.52/ As-Ga/sub 0.47/In/sub 0.53/ high-electron-mobility transistors (HEMTs) is reported. Transconductances of 465 and 650 mS/mm, respectively, were achieved. The 0.3- mu m-long gate-length device exhibited an f/sub t/>80 GHz. These results are attributed to the excellent electronic properties of the AlInAs-GaInAs modulation-doped system.<<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. >

Fabrication of a 80 nm self-aligned T-gate AlInAs/GaInAs HEMT

The authors report on the fabrication and characterization of a high-performance 80-nm self-aligned T-gate AlInAs/GaInAs high electron mobility transistor (SAGHEMT). The 80 nm*50 mu m devices reported exhibit good pinchoff characteristics, high transconductance (g/sub m/=1150 mS/mm), low output conductance (g/sub ds/=120 mS/mm at RF), and state-of-the-art current gain cutoff frequency (f/sub T/=250 GHz). Modeling and analysis indicate that it is possible to significantly improve the performance of AlInAs/GaInAs SAGHEMTs by further reducing the gate length and/or optimizing the device structure.<<ETX>>

Vertical scaling of ultra-high-speed AlInAs-GaInAs HEMTs

The scaling of the vertical dimensions of 0.15- mu m-gate-length Al/sub 0.48/In/sub 0.52/As-Ga/sub 0.47/In/sub 0.53/As high-electron-mobility transistors (HEMTs) to reduce their well-known excessive gate leakage current, premature breakdown voltage, and poor output conductance is discussed. It is found that, with a proper choice of doping densities and layer thicknesses, it is possible to realize very-high-performance AlInAs-GaInAs HEMTs (f/sub T/=160 GHz, f/sub max/=300 GHz for 0.15- mu m*50- mu m devices) with low gate leakage current, high breakdown voltage (7.0 V), and very low DC output conductance (45-mS/mm). The DC output conductance exhibits a very strong dependence on the AlInAs doping-thickness product and appears to be a limiting factor in the device power gain. By reducing the doping-thickness product, it was possible to reduce the output conductance by a factor of 3 and thus increase the power gain cutoff frequency by a factor of 1.7.<<ETX>>

InP-based HEMT's with Al/sub 0.48/In/sub 0.52/As/sub x/P/sub 1-x/ Schottky layers

In this letter we report on the DC and RF performance of InP-based HEMTs with Al/sub 0.48/In/sub 0.52/As/sub x/P/sub 1-x/ Schottky layers and GaInAs/InP composite channels. By replacing the Al/sub 0.48/In/sub 0.52/As Schottky layer with Al/sub 0.48/In/sub 0.52/As/sub x/P/sub 1-x/ we have been able to increase the bandgap of the Schottky layer and achieve record breakdown voltages for 0.15 /spl mu/m gate-length InP-based HEMTs. The 0.15 /spl mu/m gate-length HEMTs have gate-to-drain breakdown voltages of over 13 V with current densities of 620 mA/mm and maximum transconductances of 730 mS/mm. On a wafer with a higher sheet charge we have obtained gate-to-drain breakdown voltages of 10.5 V with current densities of over 900 mA/mm. These are the highest breakdown voltages reported for 0.15 /spl mu/m gate-length InP-based HEMTs with such high current densities. At 10 GHz a 450 /spl mu/m wide HEMT has demonstrated 350 mW (780 mW/mm) of output power with power-added efficiency of 60% and 12 dB gain.<<ETX>>