MHEMT with a power-gain cut-off frequency of $f_{\mathrm{max}}$ = 0.63 THz on the basis of a In$_{0.42}$Al$_{0.58}$As/In$_{0.42}$Ga$_{0.58}$As/In$_{0.42}$Al$_{0.58}$As/GaAs nanoheterostructure

The method of molecular-beam epitaxy is used to grow a In$_{0.42}$Al$_{0.58}$As/In$_{0.42}$Ga$_{0.58}$As/In$_{0.42}$Al$_{0.58}$As nanoheterostructure with a step-graded metamorphic buffer on a GaAs substrate. The root-mean-square value of the surface roughness is 3.1 nm. A MHEMT (metamorphic high-electron-mobility transistor) with a zigzag-like gate of a length of 46 nm is fabricated on the basis of this nanoheterostructure; for this MHEMT, the cutoff frequencies for the current and power gain are $f_T$ = 0.13 THz and $f_{\mathrm{max}}$ = 0.63 THz, respectively.