P. Hashimoto

GaN HFET for W-band Power Applications

In this paper we report high frequency GaN power device and measured power performance of the first W-band (75 GHz-110 GHz) MMIC fabricated in GaN material system. The first W-band GaN MMIC with 150 mum of output gate periphery produces 316 mW of continuous wave output power (power density =2.1 W/m) at a frequency of 80.5 GHz and has associated power gain of 17.5 dB. By comparison the reported state of the art for other solid state technologies in W-band is 427 mW measured in a pulsed mode on an InP HEMT MMIC with 1600 mum of output periphery (power density = 0.26 W/mm). The reported result demonstrates tremendous superiority of GaN device technology for power applications at frequencies greater than 75 GHz

GaN double heterojunction field effect transistor for microwave and millimeterwave power applications

We report development of a novel AlGaN/GaN/AlGaN double heterojunction field effect tansistor (DHFET) with improved device performance over the conventional single heterojunction GaN FET (SHFET). The GaN DHFETs with low Al content Al/sub 0.04/Ga/sub 0.96/N buffer layer exhibit three orders of magnitude lower subthreshold drain leakage current and almost three orders of magnitude higher buffer isolation than corresponding SHFET devices (600 M/spl Omega//sq. vs. 1 M/spl Omega//sq.). In GaN DHFETs with 0.15 /spl mu/m conventional T-gates we observed 30% improvement in saturated power density and 10% improvement in PAE at 10 GHz over a corresponding SHFET device.

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.

92–96 GHz GaN power amplifiers

We report the test results of a family of 92-96 GHz GaN power amplifiers (PA) with increasing gate peripheries (150 µm to 1200 µm). The 1200 µm, 3-stage PA produces 2.138 W output power (Pout) with an associated PAE of 19% at 93.5 GHz (VD=14V). The amplifier offers Pout over 1.5W with associated PAE over 17.8% in the 92–96 GHz bandwidth. The measured data show that the maximum Pout scales linearly with increasing gate periphery at an almost constant PAE around 20%. This demonstrates the high efficiency of on-chip power combining and enables W-band high power single chip solid state power amplifiers.

W-Band GaN MMIC with 842 mW output power at 88 GHz

We report W-band GaN MMICs that produce 96% more power at a frequency of 88 GHz in continuous wave (CW) operation than the highest power reported in this frequency band for the best competing solid state technology[1], the InP HEMT. W-band power module containing a single three stage GaN MMIC chip with 600 µm wide output stage produced over 842 mW of output power in CW-mode, with associated PAE of 14.7% and associated power gain of 9.3 dB. This performance was measured at MMIC drain bias of 14 V.

GaN MMIC technology for microwave and millimeter-wave applications

In this paper we demonstrate the merits of GaN MMIC technology for high bandwidth millimeter-wave power applications and for microwave robust LNA receiver applications. We report the development of a broadband two-stage microstrip Ka-band GaN MMIC power amplifier, with 15dB of flat small signal gain over the 27.5GHz to 34.5GHz frequency range and 4W of saturated output power at 28GHz, with a power added efficiency of 23.8%. This is to the best of our knowledge the best combination of output power, bandwidth and efficiency reported for a GaN MMIC in Ka-band frequency range. We also report a robust two-stage wideband (0.5GHz-12GHz) GaN LNA MMIC, which can survive 4W of incident input RF power in CW mode without input power protective circuitry. The presented LNA MMIC has, to the best of our knowledge, the best combination of NF, bandwidth, survivability and low power consumption reported to date in GaN technology.

Wideband AlGaN/GaN HEMT MMIC low noise amplifier

A 3-18 GHz AlGaN/GaN high electron mobility transistor low noise amplifier on silicon carbide is reported. The measured gain (S/sub 21/) is 20 dB +/- 2.5 dB between 3-18 GHz. The minimum measured noise figure is 2.4 dB. To the authors knowledge, this is the highest gain reported over multiple octaves up to 18 GHz using GaN technology.

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.

55% PAE and High Power Ka-Band GaN HEMTs With Linearized Transconductance via

We report small- and large-signal performances of 140-nm gatelength field-plated GaN HEMTs at Ka-band frequencies, in which the GaN HEMTs were fabricated with n+ source contact ledge. The parasitic channel resistance is reduced by ~ 50%, whereas the peak extrinsic transconductance is improved by 20% from 370 to 445 mS/mm. The GaN HEMTs with n+ source ledge exhibit improvement of maximum stable gain by at least 0.7 dB over reference devices without n+ ledge. At 30 GHz, CW output power density of 10 W/mm is measured with peak PAE of 40% and associated gain of 8.4 dB at Vds = 42 V. At Vds = 30 V, the output power density is measured as 7.3 W/mm with peak PAE of 50%, peak DE of 58%, and associated gain of 8.5 dB. The best PAE was measured as 55% at 5 W/mm at 30, 33, and 36 GHz, where the associated gains were 7.9, 7.6, and 8.2 dB, respectively.

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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.