W. Kong

Fully monolithic 4 watt high efficiency Ka-band power amplifier

Design and performance of a power amplifier that has established a new benchmark for Ka-band power is reported. The amplifier achieved >4 Watts at 25 to 31% PAE with 14 dB of power gain from 29 to 31 GHz. This output power, bandwidth, and efficiency is superior to the best previously reported results. The amplifier is implemented in an improved fully selective 0.15 um power PHEMT process.

Very high gain millimeter-wave InAlAs/InGaAs/GaAs metamorphic HEMT's

We report the first demonstration of W-band metamorphic HEMTs/LNA MMICs using an AlGaAsSb lattice strain relief buffer layer on a GaAs substrate. 0.1/spl times/50 /spl mu/m low-noise devices have shown typical extrinsic transconductance of 850 mS/mm with high maximum drain current of 700 mA/mm and gate-drain breakdown voltage of 4.5 V. Small-signal S-parameter measurements performed on the 0.1-/spl mu/m devices exhibited an excellent f/sub T/ of 225 GHz and maximum stable gain (MSG) of 12.9 dB at 60 GHz and 10.4 dB at 110 GHz. The three-stage W-band LNA MMIC exhibits 4.2 dB noise figure with 18 dB gain at 82 GHz and 4.8 dB noise figure with 14 dB gain at 89 GHz, The gain and noise performance of the metamorphic HEMT technology is very close to that of the InP-based HEMT.

High-performance double-recessed InAlAs/InGaAs power metamorphic HEMT on GaAs substrate

Double-recess power metamorphic high electron mobility transistors (MHEMTs) on GaAs substrates were successfully demonstrated. The In/sub 0.53/Al/sub 0.47/As/In/sub 0.65/Al/sub 0.35/As structures exhibited extrinsic transconductance of 1050 mS/mm and breakdown of 8.3 V, which are comparable to that of the InP power HEMT. Excellent maximum power added efficiency (PAE) of 60.2% with output power of 0.45 W/mm and record associated power gain of 17.1 dB were realized at 20 GHz. A maximum output power of 0.51 W/mm has also been demonstrated with the device. This is the first demonstration of high-efficiency K-band power MHEMTs.

High efficiency wideband 6 to 18 GHz PHEMT power amplifier MMIC

Design and performance of a power amplifier that has established new benchmarks for 6 to 18 GHz power is reported. The amplifier achieved 7.5 Watts max, 5.4 Watts average, 4 Watts min with 36 % max, 22 % average PAE and 12 dB of power gain from 6 to 18 GHz. This output power, bandwidth, and efficiency is superior to the best previously reported results. The amplifier is implemented in a fully selective 0.15 um double recess power PHEMT process.

High performance fully selective double recess InAlAs/InGaAs/InP HEMTs

InP HEMTs with a double recess 0.12 /spl mu/m gate have been developed. The material structure was designed to be fully selective etched at both recess steps for improved uniformity and yield across the whole wafer. Devices demonstrated DC characteristics of extrinsic transconductances of 1000 mS/mm, maximum current density of 800 mA/mm and gate-drain reverse breakdown voltages of -7.8 V. Power measurements were performed at both 20 GHz and 60 GHz. At 20 GHz, the 6/spl times/75 /spl mu/m devices yielded 65% maximum power added efficiency (PAE) with associated gain of 13.5 dB and output power of 185 mW/mm. When tuned for maximum output power it gave an output power density of 670 mW/mm with 15.6 dB gain and 49% PAE. At 60 GHz, maximum PAE of 30% has been measured with associated output power density of 290 mW/mm and gain of 7.4 dB. This represents the best power performance reported for InP-based double recess HEMTs.

Very high efficiency V-band power InP HEMT MMICs

State-of-the-art power performance of a V-band InP HEMT MMIC is reported using a slot via process for reducing source inductance and a fully selective gate recess process for uniformity and high yield. The 0.1 /spl mu/m gate length, high performance InGaAs/InAlAs/InP HEMTs that were utilized in the circuit exhibited a maximum power density of 530 mW/mm, power added efficiency of 39%, and a gain of 7.1 dB. At 60 GHz, a single-stage monolithic power amplifier achieved an output power of 224 mW with a PAE of 43%. The associated gain was 7.5 dB. These results are the best combination of output power and efficiency reported for an InP device and a MMIC at V-band, and clearly demonstrates the potential of the InP HEMT technology for very high efficiency, millimeter wave power applications.

Gate-Length Scaling of Ultrashort Metamorphic High-Electron Mobility Transistors With Asymmetrically Recessed Gate Contacts for Millimeter- and Submillimeter-Wave Applications

We have fabricated and characterized ultrashort gate-length metamorphic high-electron mobility transistors (HEMTs) optimized for high gain performance for millimeter- and submillimeter-wave applications. In this paper, we have systematically evaluated the impact of gate length in the range of 25-50 nm on the device performance by exploring epitaxial layer designs, gate-to-channel distances, and recess widths. The study shows the 25-nm devices underperform their 50-nm counterparts in most of the key figures of merit including output conductance, voltage gain, off-state breakdown, on-state breakdown, and, most importantly, the maximum stable gain. This observation is actually in good agreement with the state-of-the-art results published so far, which indicate that the best overall performance of HEMTs for millimeter- and submillimeter-wave applications comes from devices with gate lengths ranging from 35 to 50 nm. The 25-nm devices, on the other hand, appear to have difficulty in achieving the proper vertical scaling for optimum gain, which is limited by the minimum gate layer thickness necessary to retain good Schottky characteristics. This limitation may eventually be overcome with the adoption of new materials used as the gate layer that can be integrated into the HEMT fabrication process.

50-nm Metamorphic High-Electron-Mobility Transistors With High Gain and High Breakdown Voltages

We report the design, fabrication, and characterization of ultrahigh-gain metamorphic high-electron-mobility transistors (MHEMTs) with significantly enhanced breakdown performance. In this letter, an asymmetrically recessed 50-nm Gamma-gate process has been successfully applied to epitaxial designs with double-sided-doped InAs-layer-inserted channels grown on GaAs substrates. The critical gate recess width has been optimized for device performance, including transconductance, breakdown voltage, and gain. The employment of a device passivation process greatly minimizes the adverse impacts that the aggressive vertical and lateral scaling would have introduced for pursuing enhanced performance. As a result, we have achieved 1.9-S/mm transconductance and 800-mA/mm maximum drain current at a drain bias of 1 V, 9-V off-state breakdown voltage, approximately 3.5-V on-state breakdown voltage, and 14.2-dB maximum stable gain at 110 GHz. To our knowledge, this is a record combination of gain and breakdown performance reported for microwave and millimeter-wave HEMTs, making these devices excellent candidates for ultrahigh-frequency power applications.

3 watt Ka-band MMIC HPA and driver amplifier implemented in a fully selective 0.15 /spl mu/m power PHEMT process

The design and performance of a 0.15 um gate length fully selective recess PHEMT power amplifier that has established a new benchmark for Ka-band power is reported. The amplifiers average >3 watts at 30% PAE with 13 dB of power gain at 30 GHz, with a 1 dB gain compression output power of >2.5 watts. The P1dB output power is 2.5 times the best previously reported result for Ka-band MMIC power amplifiers. A 0.5 watt at P1dB driver amplifier is also described.

Asymmetrically Recessed 50-nm Gate-Length Metamorphic High Electron-Mobility Transistor With Enhanced Gain Performance

We report the design, fabrication and characterization of ultrahigh gain metamorphic high electron-mobility transistors. In this letter, a high-yield 50-nm T-gate process was successfully developed and applied to epitaxial layers containing high indium mole fraction InGaAs channels grown on GaAs substrates. A unique gate recess process was adopted to significantly increase device gain by effectively suppressing output conductance and feedback capacitance. Coupled with extremely small 10 mum times 25 mum via holes on substrates thinned to 1 mil, we achieved a 13.5 dB maximum stable gain (MSG) at 110 GHz for a 30-mum gate-width device. To our knowledge, this is the highest gain performance reported for microwave high electron-mobility transistor devices of similar gate periphery at this frequency, and equivalent circuit modeling indicates that this device will operate at frequencies beyond 300 GHz.