Migration of silicon atoms in planar-doped GaAsAlGaAs modulation doped fluid effect transistor heterostructures grown by molecular beam epitaxy

Photo-Hall and Shubnikov-de Hass measurements were performed on four silicon planar-doped Al0.3Ga0.7AsGaAs MODFET heterostructures. We varied the nominal silicon concentration (4.0 × 1012 and 6.2 × 1012 cm−2), the growth temperature (500 °C and 620 °C) and the distance between the planar-doped layer and the heterojunction (40 Å and 100 Å). We obtained the carrier mobility against carrier density curves by changing the carrier density using the persistent photoconductivity effect. An IR photo-diode was used to illuminate the samples. Parallel conduction in two channels, the heterojunction channel and the planar-doped layer, was observed for three samples. It was not observed for the sample grown at 500 °C with the 100 Å spacer. The effects were explained taking account of the silicon profile. Our results also indicate that, for the samples grown at 500 °C, the interface roughness is the dominant scattering mechanism limiting the mobility of the two-dimensional electron gas formed at the heterojunction, while ionized impurities are dominant for samples grown at 620 °C.