Polarization Engineering of AlGaN/GaN HEMT With Graded InGaN Sub-Channel for High-Linearity X-Band Applications

We report on the power and linearity performance of metal–organic chemical vapor deposition grown polarization-engineered novel structure that combines the AlGaN/GaN high-electron-mobility transistor with a graded InGaN sub-channel layer. The fabricated transistors with composite two-dimensional (2D) and three-dimensional (3D) electron channels showed nearly flat transconductance and power gain profiles. The maximum ${f}_{T}$ and ${f}_{ {max}}$ values of 18 GHz and 38 GHz were measured for 0.7- ${\mu }\text{m}$ gate-length transistors. Load-pull measurement at 10 GHz revealed a maximum output power of 2.2 W/mm. Two-tone measurement at 10 GHz showed an excellent OIP3 of 38 dBm for 150- ${\mu }\text{m}$ device width and a corresponding linearity figure of merit OIP3/ $\text{P}_{\textsf {DC}}$ of 9.7 dB. These results suggest that InGaN-based composite 2D–3D channel transistors could be useful for high-frequency applications requiring high linearity.