L. McCray

AlGaN/GaN heterojunction field effect transistors grown by nitrogen plasma assisted molecular beam epitaxy

In this work, we demonstrate state of the art performance of GaN HFETs grown on SiC by rf Nitrogen plasma assisted molecular beam epitaxy (MBE) at 10 and 20 GHz and good power scalability of these devices at 10 GHz. A single stage power amplifier built by power combining four of our 1 mm devices exhibits continuous wave output power of 22.9 W with associated power added efficiency (PAE) of 37% at 9 GHz. This is to the best of our knowledge the highest CW power and the best combination of power and PAE demonstrated to date for a GaN based microwave integrated circuit at this frequency.

Microwave noise performance of AlGaN-GaN HEMTs with small DC power dissipation

We report low microwave noise performance of discrete AlGaN-GaN HEMTs at DC power dissipation comparable to that of GaAs-based low-noise FETs. At 1-V source-drain (SD) bias and DC power dissipation of 97 mW/mm, minimum noise figures (NF/sub min/) of 0.75 dB at 10 GHz and 1.5 dB at 20 GHz were achieved, respectively. A device breakdown voltage of 40 V was observed. Both the low microwave noise performance at small DC power level and high breakdown voltage was obtained with a shorter SD spacing of 1.5 /spl mu/m in 0.15-/spl mu/m gate length GaN HEMTs. By comparison, NF/sub min/ with 2 /spl mu/m SD spacing was 0.2 dB greater at 10 GHz.

Submicron enhancement-mode AlGaN/GaN HEMTs

Most recent GaN-based HEMT technology has been focused toward microwave power applications. In this work, we report DC and RF characteristics of the first E-mode AlGaN/GaN HEMTs fabricated down to 0.2 /spl mu/m gatelength, and having an f/sub t/ reaching 25 GHz. Further improvement of E-mode GaN HEMTs could open potential applications for mixed-signal ICs with a high dynamic range.

Confinement of high Be doping levels in AlInAs/GaInAs npn heterojunction bipolar transistors by low temperature molecular‐beam epitaxial growth

AlInAs/GaInAs npn heterojunction bipolar transistors (HBTs) have been grown over a substrate temperature range of 280–450u2009°C with Be base doping levels ranging from 2.0×1019 to 1.6×1020 cm−3. We have determined that for a desired base doping level there exists an optimum growth temperature at which the Be is confined in the base and at the same time the dc current gain of the HBT is maximized.

Monolithic fabrication of NPN and PNP AlInAs/GaInAs HBTs

The authors demonstrated the feasibility of a new technique for the monolithic fabrication of complementary heterostructure bipolar transistors (HBTs). The process led to coplanar npn and pnp HBTs, the first in the AlInAs/GaInAs material system, which were comparable with the state of the art in HBTs. These devices exhibited unity current gain cutoff frequencies (f/sub T/) up to 99 GHz and 14 GHz for the npn and pnp transistors, respectively. The fabrication scheme allows each of these device types to have individually designed epitaxial structures that are grown in a single molecular beam epitaxy run. Results show that the devices will be capable of tight packing densities for IC applications.<<ETX>>

36-GHz static digital frequency dividers in AlInAs-GaInAs HBT technology

Summary form only given. Static divide-by-four circuits have been fabricated that operate up to 36 GHz using AlInAs-GaInAs heterojunction bipolar transistor (HBT) IC technology processing an f/sub t/ and f/sub max/ of 110 and 73 GHz, respectively. The transistors used consisted of an abrupt emitter-base junction design which incorporated a low-temperature p-GaInAs spacer as part of the base to inhibit beryllium diffusion. The AlInAs-GaInAs HBT device layers were grown lattice-matched to semi-insulating InP substrates by solid-source molecular beam epitaxy (MBE). >

GaN HFETs with excellent low noise performance at low power levels through the use of thin AlGaN Schottky barrier layer

State-of-the-art noise performance of AlGaN/GaN HFETs in the 2-20 GHz frequency range for ultra low power operation of 10 mW (10 mA drain current and 1 V drain bias) is reported. A record low minimum noise figure (NF/sub min/) of 0.4 dB with 16 dB associated gain at 5 GHz was measured. The NF/sub min/ is below 0.8 dB across the 2-12 GHz frequency-band, with associated gains of better than 12.5 dB. This noise performance is achieved by using a vertically scaled device structure where the thickness of the AlGaN Schottky layer is reduced to 15 nm compared to the standard thickness of 30 nm previously used for our baseline devices. Indeed. NF/sub min/ of the scaled device is better than the baseline device across the 2-20 GHz band.

GaN HFETs on SiC Substrates Grown by Nitrogen Plasma MBE

AlGaN/GaN heterojunction field effect transistors (HFETs) have recently demonstrated power-handling capabilities exceeding by almost an order of magnitude those of GaAs-pHEMTs. In addition, several groups have reported that low-noise performance of these high power devices almost matches that of the state of the art GaAs-pHEMTs, despite the relative immaturity of GaN HFET technology. A growing demand for GaN HFET parts that has been created by the recent promising performance of GaN HFETs led to the expansion of our research effort to include a small-scale production capability. Device results and run-to-run reproducibility data presented in this paper clearly demonstrate, that plasma assisted MBE is a viable tool for production of GaN HFETs on SiC wafers.

GaN HFET technology for RF applications

GaN HFET has emerged as a very promising device technology for next-generation microwave applications. The last several years have witnessed a tremendous progress in the development of this technology, from material growth to circuit demonstration. Devices and circuits with excellent output power, power density, efficiency, and noise figure have been achieved. This talk reviews the current status of GaN HFET technology.

K-band GaN power HFET's with 6.6 W/mm CW saturated output power density and 35% power added efficiency at 20 GHz

AlGaN/GaN heterostructure field effect transistors (HFETs) grown on SiC substrates are currently the most powerful three-terminal microwave solid state devices. While the power performance of these devices is well documented at X-band frequencies, there is growing interest in these devices at higher frequencies. In this study we characterize the power performance of GaN HFETs at 20 GHz. Our results clearly show that GaN HFETs have strong potential for power applications at K-band frequencies and beyond.