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 transconductanceprofiles. Maximum f
_T
and fmax of 23 and 65 GHz were measured for 0.7-μm gate-length transistors, corresponding to an f
_T
-L
_G
product of 16.2 GHz·μm. 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-μm device width and a corresponding linearity figure-of-merit OIP3/PDC of 3.4 dB. These results suggest that PolFETs could be useful for high-frequency applications requiring high linearity.