Hirotaka Amasuga

A high power density TaN/Au T-gate pHEMT with high humidity resistance for Ka-Band applications

A 0.8 W/mm high power pHEMT with high humidity resistance is reported. By using tantalum nitride as the refractory gate metal and a silicon nitride layer prepared by a catalytic chemical vapor deposition technique for passivation of this transistor, tough moisture resistance was obtained showing no Id degradation even after 500 hours at 130 degrees centigrade and 85% humidity. Moreover, the Schottky breakdown voltage of the TaN gate is higher than that of a WSiN gate. A one-stage prematched amplifier with the new pHEMT has achieved 0.83 W/mm output power at Vds = 8 V, with 8.5 dB gain and 40% power added efficiency in the Ka-band. These are some of the highest power figures ever reported.

A V-Band High Power and High Gain Amplifier MMIC using GaAs PHEMT Technology

We report the performance of a V-band 5-stage high power amplifier MMIC using a millimeter-wave 0.1 mum GaAs pHEMT. It has demonstrated that an output power of 28.8 dBm (759 mW) at 1 dB compression point with 17.8 dB power gain and 14.2% PAE at 59 GHz. And it delivers an output power of 28.9 dBm (776 mW) at a saturation point. These results represent, to the best of our knowledge, the highest output power and power gain for single-ended MMICs.

A Low 1/f Noise and High Reliability InP/GaAsSb DHBT for 76 GHz Automotive Radars

To develop a low 1/f noise and high reliability InP/GaAsSb DHBT, experimental analyses on the recombination current have been carried out. The results show that the recombination current that can affect 1/f noise and reliability originates from the surface of the base. We have optimized the ledge and passivation film on the base surface of InP/GaAsSb DHBT. The optimized DHBT offers 7 dB lower 1/f noise level than the non-optimized DHBT. Additionally, in the high temperature burn-in test, no degradation has been induced even after 1,000 hr. It can satisfy the criterion of automotive radars. The W-band oscillator with the optimized DHBT delivers a remarkably low phase noise of -107 dBc/Hz at 1MHz-offset. This phase noise is 10 dB lower than that of the non-optimized HBT oscillator. These results experimentally confirm that decreasing 1/f noise is effective for the design of a low phase noise oscillator using InP/GaAsSb DHBT. To our knowledge, this is the first report to reveal that the base surface structure of InP/GaAsSb DHBT is a key factor in the improvement of reliability and phase noise.

A Nonlinear Drain Resistance pHEMT model for Millimeter-wave High Power Amplifiers

A high power pHEMT with longer drain-gate separation can operate at higher voltage. However, it shows large output power loss at millimeter-wave in addition to the conventional parasitic power dissipation. The nonlinear drain resistance Rd of the pHEMT is found to cause the large power loss, although it behaves as a conventional resistor at low frequency. The nonlinearity of the Rd is modeled and shows good agreement with the measurement. Comparisons of pHEMTs with different nonlinear Rd also support the model.