Magneto-optics and valence-band discontinuity in a HgTe-Hg1−xCdxTe superlattice

We report here on infrared magneto-optical studies of band gaps and electron cyclotron resonances of a narrow-gap HgTe-${\mathrm{Hg}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Cd}}_{\mathit{x}}$Te superlattice. The experimental electron effective mass at the conduction-band edge and four different interband transition energies are compared to the prediction of a 8×8 k⋅p band-structure calculation in order to determine the valence-band discontinuity between HgTe and CdTe. At liquid-helium temperatures an excellent description of the experiment is obtained with a band offset of 550 meV. Agreement between experiment and theory is not satisfactory with the valence-band offset of 350 meV as deduced from x-ray and ultraviolet photoelectron spectroscopy.