Study of Low Noise with High Linearity AlGaN/GaN HEMTs by Optimizing Γ-Gate Structure for Ka-Band Applications

This paper investigates the device noise and linearity of an AlGaN/GaN HEMT with an optimized Γ-Gate structure for Ka-band applications. The Γ-Gate was used to provide low gate resistance for the device by increasing the gate cross-section and acting as a gate field plate to achieve a flat transconductance (G_m) profile. The device’s G_m profile was analyzed under different gate positions, including at the center or close to the source. Under different bias conditions, we performed the optimization of the Γ-gate head length (L_head). The results show that an excellent minimum noise figure (NF_min) for the device can be achieved when the Γ-gate is positioned close to the source with an optimum L_head. Finally, the NF_min improved from 1.9 dB to 1.59 dB and the third-order intercept point (OIP3) value improved from 27.7 dBm to 31.1 dBm when the source-drain distance (L_SD) was reduced from 2.5 μ m to 2 μ m . It was demonstrated that the optimized Γ-Gate design has the potential to attain the device with low noise and high linearity.