RF performance improvement of metamorphic high-electron mobility transistor using (In_xGa_1-xAs)_m(InAs)_n superlattice-channel structure for millimeter-wave applications

High-performance metamorphic high-electron mobility transistors (MHEMTs) using an (In_xGa_1-xAs)_m(InAs)_n 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_xGa_1-xAs) _m(InAs)_n channel layer. When biased at 1.2 V, the current gain cutoff frequency (f_T) and the maximum oscillation frequency (f_max) were extracted to be 304 and 162 GHz, respectively. As for noise performance, the device demonstrated a 0.75-dB minimum noise figure (NF_min) 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.