Low-temperature transport properties in AlxGa1−xAsySb1−y/InAs quantum wells: Well-width dependence

Low-temperature magneto-transport properties of AlxGa1−xAsySb1−y/InAs deep quantum wells (QWs) with different well widths (Lw=15–500 nm) and their dimensionality were studied. The Hall data were analyzed by means of the two-carrier model: coexistence of electrons and holes for Lw=15–150 nm and existence of two types of electrons with different mobility for Lw=300 and 500 nm. The profile of perpendicular magnetoresistance (MR), ρxx(B⊥) for the two-dimensional electrons (2DEs) in narrow QWs (Lw=15 and 50 nm) can be divided into the following four regimes: (1) the negative MR due to the weak localization (WL) in extremely low B-fields, (2) the crossing of ρxx for different temperatures at Bc=1/μe in moderate B-fields due to the orbital effect on the electron–electron interaction, (3) the Shubnikov–de Haas oscillations and (4) the quantum Hall effect in high-B fields. As for the in-plane MR except in the very low-field region characterized by the WL, Δρxx(B∥)/ρ0 always starts from a negative one essentially independent of T, which was explained by the classical boundary scattering at the wall of the barrier in quasi-ballistic regime. The quantum Hall resistance of the electron–hole system has also been discussed.