Charge Scattering Mechanisms In Shallow Inas Quantum Wells

We studied the charge scattering mechanisms present in In0.2Al0.8Sb/InAs/Al0.8Ga0.2Sb wells placed in close proximity to the surface of the heterostructures, at depths from 7nm to 15nm. The heterostructures were either unintentionally doped, doped from below the channel, or from above the channel. Measurements of sheet and Hall resistances were performed at T=2K in a variable magnetic field and under illumination with wavelengths of 400nm up to 1300nm. The charge density dependencies of the Hall mobility and quantum scattering time were used to infer the dominant scattering mechanisms. We found that the surface proximity induces significant band bending and an asymmetric placement of the charge distribution in the well. The result is an increase in interface roughness scattering, which reduces the mobility and the quantum scattering time values. In addition, the quantum scattering time is sensitive to scattering off charged impurities, remote or close to the well. Top doping restores the band profile symmetry and improves the transport. A symmetric profile, however, lowers the expectations for a strong spin-orbit coupling and spintronic applications.