RF Performance Improvement of Metamorphic High-Electron Mobility Transistor Using $(\hbox{In}_{x}\hbox{Ga}_{1 - x}\hbox{As})_{m}/(\hbox{InAs})_{n}$ Superlattice-Channel Structure for Millimeter-Wave Applications
High-performance metamorphic high-electron mobility transistors (MHEMTs) using an (In<sub>x</sub>Ga<sub>1-x</sub>As)<sub>m</sub>/(InAs)<sub>n</sub> superlattice structure as a channel layer have been fabricated successfully. These HEMTs with 80-nm gate length exhibited a high drain current density of 392 mA/mm and a transconductance of 991 mS/mm at 1.2-V drain bias. Compared with a regular In_xGa_1 - xAs channel, the superlattice-channel HEMTs showed an outstanding performance due to the high electron mobility and better carrier confinement in the (In<sub>x</sub>Ga<sub>1-x</sub>As)<sub>m</sub>/(InAs)<sub>n</sub> channel layer. When biased at 1.2 V, the current gain cutoff frequency (f<sub>T</sub>) and the maximum oscillation frequency (f<sub>max</sub>) were extracted to be 304 and 162 GHz, respectively. As for noise performance, the device demonstrated a 0.75-dB minimum noise figure (NF<sub>min</sub>) with an associated gain of 9.6 dB at 16 GHz. Such superior performance has made the devices with a superlattice channel well suitable for millimeter-wave applications.