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Shinichi HOSHI Takayuki IZUMI Tomoyuki OHSHIMA Masanori TSUNOTANI Tamotsu KIMURA
The reduction of the drain current for InGaAs/AlGaAs pseudomorphic high electron mobility transistors (PHEMTs) has been observed due to the RIE-damage induced under the gate region. However, it has been found that the drain current can be recovered after the gate-drain reverse current stress even at room temperature. The recovery rate of the drain current strongly depends on the gate-drain reverse current density. The activation energy of the recovery rate has been confirmed to decrease from 0.531 eV to 0.119 eV under the gate-drain reverse current stress. This phenomenon can be understood as a recombination enhanced defect reaction of holes generated by the avalanche breakdown. The non-radiative recombination of holes at the defect level is believed to enhance the recovery of the RIE-damage.
Hiroyuki NAKANO Norihiro OKUMURA Akinori MAEDA Hideo FURUHASHI Toshio YOSHIKAWA Yoshiyuki UCHIDA Kenzou KOJIMA Asao OHASHI Shizuyasu OCHIAI Teruyoshi MIZUTANI
Vanadyl-phthalocyanine (VOPc) single crystals were prepared on KBr substrate by molecular beam epitaxy (MBE). Their maximum size is 1380.16 µm3. The morphology of the VOPc single crystal was investigated from the results of UV/VIS spectra and RHEED. They suggest that the VOPc single crystal may be grown with pseudomorphic layers. The growing process was expained by Volmer-Weber model. The third order nonlinear optical property of VOPc single crystal was measured with Maker fringe method. The value of the third order optical susceptibility (χ(3)) of VOPc single crystal was estimated to be about 10-9 esu from the result of Maker fringe.
Takuo KASHIWA Takayuki KATOH Naohito YOSHIDA Hiroyuki MINAMI Toshiaki KITANO Makio KOMARU Noriyuki TANINO
An ultra low noise 50-GHz-Band amplifier (LNA) MMIC has been developed using an AlGaAs/InGaAs pseudomorphic HEMT. A noise figure of 1.8 dB with an associated gain of 8.1 dB is achieved at 50 GHz. The noise figure is less than 2.0 dB from 50 GHz to 52.5 GHz. This is the state-of-the-art noise figure for low noise amplifiers around 50 GHz. The success of this LNA development came from the excellent HEMT and MMIC technologies and the accurate modeling of active and passive elements. Good agreement between measured and simulated data over the band from 40 GHz to 60 GHz is obtained.
Yasuyuki SUZUKI Hikaru HIDA Tetsuyuki SUZAKI Sadao FUJITA Akihiko OKAMOTO
Recessed-gate DMTs (doped-channel hetero-MISFETs) with i-AlGaAs/n-GaAs structure and pseudomorphic i-AlGaAs/n-InGaAs/i-GaAs structure have been developed. Broad plateaus in gm and fT provide evidence that the DMTs make the devices suitable for high-speed large-signal operation. GaAs DMTs with 0.35 µm-length have gate turn on voltage of 0.7 V, maximum transconductance of 320 mS/mm and fT of 41 GHz. Pseudomorphic DMTs have gate turn on voltage of 0.9 V, maximum transconductance of 320 mS/mm, fT of 42 GHz and have the enhanced advantages of high current drivability and large gate swing. Further more, with the use of the recessed-gate DMTs, a high-speed laser driver IC for multi-Gb/s optical communication systems are demonstrated. This laser driver IC operates at 10 Gb/s with rise and fall times as fast as 40 psec, and it can drive up to 60 mA into a 25 Ω load.