Accumulation of Localized Electrons in Sn Doped InSb/AlxIn1−xSb Quantum Wells

We examined the role of localized electrons in the accumulation layer of Sn-doped InSb quantum wells (QWs) with various wellwidths . At liquid He temperatures, the samples with the sheet resistance ρ>ρc=h/e2 for exhibit the variable-range hopping (VRH), while those with exhibit weak localization (WL), where ρc is the quantum resistance. In particular, a part of the electrons (with density of ) from Sn donors are trapped at the interface states at low temperatures below 77 K. In the WL regime, we observed the small positive magnetoresistance (MR) peak arising from the weak anti-localization (WAL) in the presence of spin-orbit interaction (SOI). In contrast to the WAL in WL regime, the low-field MR in the VRH regime remains entirely negative surviving the SOI, indicating that the hopping MR due to the quantum interference (QI) is completely negative regardless of the SOI. This result supports the predictions based on the directed-path approach for forward-scattering paths ignoring the back-scattering return loops for the QI in the VRH.