X-Band Power and Linearity Performance of Compositionally Graded AlGaN Channel Transistors

We report on the power and linearity performance of metal organic chemical vapor deposition grown AlGaN channel polarization-graded field-effect transistor (PolFET). The fabricated transistors with 3-D electron channels showed nearly flat transconductance profiles. Maximum {f}_{T} and {f}_{\text {max}} of 23 and 65 GHz were measured for 0.7- \mu \text{m} gate-length transistors, corresponding to an {f}_{T} - {L}_{G} product of 16.2 GHz \cdot \mu \text{m} . Load-pull measurement at 10 GHz revealed a maximum output power of 2 W/mm with a maximum small signal gain of 16 dB. Two-tone measurement at 10 GHz showed an OIP3 of 33 dBm for 150- \mu \text{m} device width and a corresponding linearity figure-of-merit OIP3/ \text{P}_{\text {DC}} of 3.4 dB. These results suggest that PolFETs could be useful for high-frequency applications requiring high linearity.