Interface roughness scattering of electrons in a [411]A In/sub 0.53/Ga/sub 0.47/As/In/sub 0.52/Al/sub 0.48/As HEMT structure with super-flat interfaces

InP-based InGaAs/InAlAs high electron mobility transistors (HEMTs) have demonstrated excellent high-frequency and low-noise performance due to their high saturation velocity of electrons in an InGaAs channel layer. Recently, we have reported that effectively atomically flat InGaAs/InAlAs interfaces over a wafer-size area ["[411]A super-flat interfaces"] can be formed in lattice-matched and pseudomorphic InGaAs/InAlAs quantum wells (QWs) grown on [411] A-oriented InP substrates by molecular beam epitaxy (MBE), and the highest mobility (90,500 cm/sup 2//Vs with two dimensional electron gas (2DEG) concentration of 3.1/spl times/10/sup 12/ cm/sup -2/ at 77 K) of 2DEG for InGaAs/InAlAs HEMT structures was achieved in the [411]A pseudomorphic InGaAs/InAlAs HEMT structure. In this study, we have investigated the low temperature (20 K) 2DEG mobility in the lattice-matched InGaAs/InAlAs HEMT structure grown on the [411]A InP substrate with changing N/sub s/ by gate-biasing, and we found that interface roughness scattering in the [411]A sample was much smaller than that of an usual [100] sample.