High electron mobility transistors (HEMTs) with a pseudomorphically strained InAs channel (InAs-PHEMTs) were fabricated, and their high frequency characteristics were estimated by measuring the S-parameters. For a VDS
of 1.4 V and VGS
of 0.3 V, InAs-PHEMTs showed an excellent intrinsic cut-off frequency (f
T, int.) as high as 90 GHz regardless of their longer LG
(0.7 μm). Since fT
is known to be inversely proportional to LG
to the first approximation, f
T, int. of our InAs-PHEMTs may reach 630 GHz if their LG
is reduced to 0.1 μm.
Moreover, we calculated the InAs-PHEMTs' energy state and potential profile by self-consistently solving the Schrödinger and Poisson equations. In solving the Schrödinger equation, the energy-dependent effective mass was employed to take into account the strong non-parabolicity of InAs conduction-band based on the k·p perturbation theory by E. O. Kane. It was clarified that most electrons are confined to the InAs layer. On the contrary, if the non-parabolicity is not taken into account, electrons will spread over the InGaAs channel layer.