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.