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K. Takagi,
K. Matsushita,
K. Masuda,
S. Nakanishi,
T. Soejima,
H. Sakurai,
K. Onodera,
J. Shim, H. Kawasaki,
Y. Takada,
M. Hirose,
K. Tsuda
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ABSTRACT: AlGaN/GaN High Electron Mobility Transistors(HEMTs) were developed with an achievable fmax of 138GHz. A 6.4mm gate periphery device was thereafter designed with pre-match circuits on the die and matching circuits on an alumina substrate at Ka-band. A saturated output power of 18.5W was achieved at 31GHz which to the best of our knowledge is the highest ever reported at Ka-band.
Microwave Symposium Digest (MTT), 2011 IEEE MTT-S International; 07/2011
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ABSTRACT: AlGaN/GaN High Electron Mobility Transistors(HEMTs) were developed for Ka-band. The developed device showed 138 GHz of fmax, which depended on the thickness of the AlGaN barrier layer and the gate length. It had a 6.4 mm gate periphery on a metal carrier plate. The output power achieved 20 W with impedance matching circuits.
Compound Semiconductor Integrated Circuit Symposium (CSICS), 2010 IEEE; 11/2010
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ABSTRACT: AlGaN/GaN high electron mobility transistors (HEMTs) were improved for X-band and Ku-band applications. The power added efficiency (PAE) was achieved over 40% for X-band and over 30% for Ku-band. The developed devices combined two AlGaN/GaN HEMTs of 12 mm gate periphery and exhibited the output power of over 50 W. An AlGaN/GaN HEMT with four dies of 12 mm gate periphery was developed and exhibited the output power of over 120 W.
Microwave Symposium Digest, 2009. MTT '09. IEEE MTT-S International; 07/2009
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ABSTRACT: AlGaN/GaN high electron mobility transistors (HEMTs) were developed for Ku-band applications. The operating voltage characteristics in CW operating conditions were investigated. The developed AlGaN/GaN HEMT with combined two dies of 12 mm gate periphery exhibits output power of over 30 W with a power added efficiency (PAE) of 12% under VDS = 30 V, CW operating condition at 14.25 GHz, and a gain compression level of 3 dB.
Microwave Integrated Circuit Conference, 2007. EuMIC 2007. European; 11/2007
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ABSTRACT: AlGaN/GaN HEMTs devices are fabricated on 3-inch SiC misoriented substrates. The misorientation angle, as measured from the wafer surface normal to the axis perpendicular to the (0001) c-plane, is varied from 0.06° to 0.47°. The surface morphology and wafer crystalline quality were investigated by using AFM and PL. Analysis of the data reveals the relationships between the SiC substrate misorientation and both the physical characteristics of the grown epi layer and the performance of the fabricated device. . INTRODUCTION AlGaN/GaN HEMTs devices are studied intensively for applications such as high power microwave devices [1, 2] for satellite communication systems and fixed wireless access systems. Because of its good thermal conductivity and its lattice constant close to that of GaN, SiC can be used as AlGaN /GaN epitaxial substrates. Additionally, these characteristics enables device to operate at higher power density. There are some reports about influences on epitaxial layer quality on off-angle SiC or Sapphire wafer caused by off-angle [3-6]. In this work, we investigated the characteristics of HEMTs devices on misoriented SiC substrates and it is found that the device performances strongly depend on amount of misoriented angle. EXPERIMENT The Al0.25Ga0.75N/GaN epitaxial layers were grown on vicinal 3-inch SiC substrates by MOCVD. The off-angles of substrates used are varied from 0.06° to 0.47° from the axis along with (0001) c-plane. HEMTs devices are fabricated on these wafers. Before the device fabrication, epitaxial wafers are determined by atomic force microscopy (AFM) and photoluminescence (PL). PL measurements were carried out with 325nm He-Cd laser. Figure 1 shows a cross sectional view of fabricated HEMTs. The fabrication process began with mesa isolation by ICP-RIE etching. Next, Ti/Al were evaporated by E-beam thermal evaporator and annealed with RTA at N2 ambient to form the source and drain electrodes. A Schottky gate electrode was formed with E-beam evaporated Pt/Au. SiN film was deposited by PE-CVD for surface passivation.
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ABSTRACT: AlGaN/GaN HEMTs devices are studied intensely because of its ability of operation at higher voltage with higher power density. As the study progress, it is realized that the reliability of the fabricated device is a quite important issue. From the reliability study of AlGaN/GaN HEMTs, it is found that the current degradation has relationships with the isolation structure. In this paper, the differences of current degradations between two isolation methods are studied and some interpretations concerning the source of these degradations are discussed.
