Ultrahigh electron and hole mobilities in zero-gap Hg-based superlattices

Transport measurements on five HgTe/CdTe and Hg_1-xZnₓTe/CdTe superlattices have yielded the highest p-type mobilities ever reported for a II-VI semiconductor (> 10⁵ cm²/Vs). The temperature dependence of the intrinsic carrier density indicates near-zero energy gaps in all of the samples. Theoretical band-structure calculations by the tight-binding method are consistent with the experimental results in that they predict not only zero band gap but also electron and hole effective masses which are both considerably less than 0.01m₀. Further features of the calculated band structure are mirrored in the data, such as a near equality of the electron and hole masses, "mass broadening" of the holes, and an extreme nonparabolicity of the highest valence band.