The off-state shunt GaAs FET, which is the most important for low distortion operation of the high power RF switch IC, is a very complicated device to analyze the RF voltage. Because the conventional measurement method has an influence on the behavior of the switch, it has not provided the correct measurement value. In this paper, we have realized a measurement method without touching the surface of the switch IC using EO-probe. As a result we achieved extremely low second and third harmonics of 70.5 dBc and 75.2 dBc, respectively at the input power of 35 dBm by adoptin SPDT switch IC composed of the multi-gate FET for the thru FET and the stacked-gate FET.

We report 0.15-µm T-shaped gate MODFETs using BCB (Benzocyclobutene) as low-k spacer dielectric material. The RF performance of pseudomorphic MODFET was improved by reducing the gate fringing capacitance using low-k material. The BCB film was deposited by plasma CVD technique at 100C and was patterned by lift-off technique. The dielectric constant of BCB film deposited by plasma CVD was confirmed 2.7, which is equal to that of spin-coated BCB, and is 35% lower than that of conventional SiO2. The leakage current was 4.710-5 A/cm2 at 3.6 MV/cm and was low enough for spacer material. 0.15-µm T-shaped gate MODFETs were fabricated by using BCB spacer and phase-shift lithography technique. More than 20 GHz increase of fmax was obtained in comparison with conventional SiO2 spacer by reducing the gate fringing capacitance.

High output power AlGaN/GaN metal-insulator-semiconductor (MIS) hetero-junction field effect transistor (HFET) on Si substrate for millimeter-wave application has developed. High temperature chemical vapor deposition (HT-CVD) grown SiN as a gate insulator improves the breakdown characteristics which enables the operation at high drain voltage of 55 V. The device exhibits high drain current of 1.1 A/mm free from the current collapse and high RF gain of 10.4 dB. The amplifier module developed AlGaN/GaN MIS-HFET with the gate width of 5.4 mm exhibits an output power of 10.7 W and a linear gain of 4 dB at 26.5 GHz. The resultant high output power is very promising for long-distance communication at millimeter-wave in the future which would enable high speed and high density data transmission.