We report a high maximum frequency of oscillation (f $_{max}$ ) and a current-gain cutoff frequency (f $_{T}$ ) of 800 and 260 GHz, respectively, with pseudomorphic high-electron mobility transistor (PHEMT), using an InGaAs/InAs composite channel and an asymmetric gate recess. This result was achieved with long gate length L $_{G} = 75$ nm. The RF small signal equivalent circuit (SSEC) was extracted up to 110 GHz. Moreover, noise parameters extraction gives a minimum noise figure (NF $_{min}$ ) of 0.8 dB (with associated gain G $_{ass} = 16$ dB) and 1.8 dB (with associated gain G $_{ass} = 11.6$ dB) at 40 and 94 GHz, respectively. In this study, the gate leakage current was considered in the SSEC of the transistor (g $_{gf}$ and g $_{df}$ ) and for extraction of the noise parameters.

The field of applications of tunable microwave oscillators is now growing up : local oscillators, Doppler radars, microwave sources for LAN... These applications require an important frequency stability. We describe hereafter such an oscillator which is made in GaAs monolithic technology, uses MESFETs and which can be easily frequency-stabilized.

In this work, we present a wideband on-wafer characterization technique for InAlAs/InGaAs/InAs InP-based high-electron mobility transistors (HEMTs) using an optimized multiline Thru-Reflect-Line (mTRL) calibration kit. Our goal is to directly extract transition frequency f_T and maximum frequency of oscillation f_max values from S-parameters measurements with frequencies up to 1.1 THz and overcome the limitations of the traditional 20 dB/dec extrapolation method using lower-frequency band measurements. Indeed, as the state-of-the-art transistors now exhibit cutoff frequencies exceeding 1 THz, standard low-frequency extrapolation methods become increasingly inaccurate. Full-wave electromagnetic simulations were used to design low-loss coplanar waveguide (CPW) access structures with stable impedance and minimal parasitic effects. These structures were co-fabricated with HEMTs and calibration standards on the same InP substrate. The 2-finger transistor with a 80 nm gate length exhibits a directly measured f_T = 320 GHz and f_max = 800 GHz. The technique showed high consistency across six frequency bands and confirms that direct broadband measurement with mTRL improves accuracy. This work highlights the metrological strength of mTRL-based setups for next-generation THz device characterization.