Self-biasing effects induced by RF step-stress in Ka-band LNAs based on InAlN/GaN HEMT technology

Nitride technologies are proposing a large variety of active devices to address high-power modules, but also robust low-noise receivers at high frequencies. High Electron Mobility Transistors (HEMT) are essentially developed on AlGaN/GaN heterostructure, but InAlN/GaN alternative seems very promising due to lattice matched layers (using 17% of In content) at the interface between layers where the channel (2DEG) occurs, and to a better mobility in the 2DEG. This paper presents a study on Ka-band Low Noise Amplifiers featuring a Noise Figure of 3.3dB between 29–30.5 GHz for the single stage version under study. RF step-stresses and CW stresses have been applied on four different LNAs, evidencing fluctuation of charges in the active device. Self-biasing of the HEMT is emphasized and assessed through the evaluation of the 2 nd order harmonic at 59 GHz. Initial noise and dynamic performances can be fully recovered after a long period with no RF signal, or by applying a positive voltage on the gate to remove charges under the gated zone of the transistor. These results on the stability of the noise figure of LNAs prove that jamming signals can be harmless on GaN based receivers, even if some more improvements have to be achieved on these not yet mature technologies.