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We have investigated the anisotropic transport behavior of InAs/AlSb heterostructures grown on a (001) InP substrate. An electrical analysis showed anisotropic sheet resistance Rsh and electron mobility μn in the two dimensional electron gas (2DEG). Hall measurements demonstrated an enhanced anisotropy in μn when cooled from room temperature to 2 K. High electron mobility transistors exhibited 27% higher maximum drain current IDS and 23% higher peak transconductance gm when oriented along the [1-10] direction. The anisotropic transport behavior in the 2DEG was correlated with an asymmetric dislocation pattern observed in the surface morphology and by cross-sectional microscopy analysis of the InAs/AlSb heterostructure.

It is shown that the electron-phonon interaction at a conducting interface between a topological insulator thin film and a semiconductor substrate can be directly probed by means of high-resolution Brillouin light scattering (BLS). The observation of Kohn anomalies in the surface phonon dispersion curves of a 50 nm thick Bi2Te3 film on GaAs, besides demonstrating important electron-phonon coupling effects in the GHz frequency domain, shows that information on deep interface electrons can be obtained by tuning the penetration depth of optically-generated surface phonons so as to selectively probe the interface region, as in a sort of quantum sonar.