AlGaN/GaN HEMTs on Silicon With a Graded-AlGaN Back-Barrier for RF Applications

In this study, we report on the electrical characteristics of AlGaN/GaN HEMT fabricated on a GaN-on-Si buffer scheme with a reverse-graded AlGaN back-barrier. Transistors exhibited a maximum DC drain current of 0.8 A/mm with a peak transconductance of 280 mS/mm. Devices exhibited off-state breakdown voltage greater than 100V, indicating good channel control even without compensation dopants. The current collapse in these devices was approximately 12% under drain-lag pulsed-IV measurements, indicating minimal trapping in this buffer scheme. RF small-signal measurements yielded peak f
t
/f
max
figures of 31/72 GHz, respectively. A peak output power of 2.36 W/mm was obtained in pulsed load-pull measurements at 4 GHz with a Power-Added-Efficiency (PAE) of 18.1%.