Quantum well mobility and the effect of gate dielectrics in remote doped InSb/AlxIn1 - xSb heterostructures

Low- and high-field magnetotransport measurements on 30 nm δ-doped InSb/AlInSb quantum wells with different doping densities are reported. Mobilities over the temperature range 2 to 290 K are described using the relaxation time approximation. Screening by electrons in the doping plane and the temperature variation of the Fermi wave vector and effective mass of the carriers are incorporated into the model. High quality, Shubnikov de Haas oscillations are observed in samples that exhibit single sub-band occupancy. However, higher density samples that show considerable parallel conductance with qualitatively poor ρ_xx(B) are shown to recover high quality Shubnikov de Haas oscillations by deposition of a surface gate with a SiO₂ gate dielectric. We show that the incorporation of this gate dielectric significantly modifies the transport properties and results in an increased mobility over ungated structures with the same carrier density. These observations lead to further insight into the carrier scattering mechanisms present in these InSb/AlInSb structures.