Evaluation of Power and Linearity at 30 GHz in AlGaN/GaN HEMT Fabricated by Integrating Transistors With Multiple Threshold Voltages

In this work, using the multiple threshold voltages (multi- {V}_{\text {Ths}}{)} coupling technology introduces an innovative approach to leverage AlGaN/GaN-based high-electron-mobility transistor (AlGaN/GaN HEMT) for high linearity millimeter-wave (mm-W) applications. As a result of optimizing the etching depth of the recessed trench ( {H}_{R} ), the fabricated composite HEMT demonstrated a remarkably flat transconductance ( {G}_{m} ) plateau, and well-maintained profile of small-signal characteristics as a function of gate voltage. As a consequence, at a biased drain voltage of 10 V and a frequency of 30 GHz, the composite HEMT achieved the highest ratio of output third-order intercept point (OIP3) to DC power consumption ( {P}_{\text {DC}}{)} , denoted as (OIP3/ {P}_{\text {DC}}{)} , measuring ~ 9.3 dB. Simultaneously optimizing the bias conditions, the devices showcased a remarkable combination of high one-tone saturated output power density reaching 6.5 W/mm and two-tone OIP3/ {P}_{\text {DC}} of ~ 6.1 dB, achieved at a biased drain voltage of 25 V. The experimental results provide compelling evidence of the attractiveness of the multi- {V}_{\text {Ths}} coupling technique for millimeter wave RF transmitters.