Direct evidence for the inverted band structure of HgTe

Angular-resolved photoemission measurements of the nonpolar (110)-cleavage face of HgTe single crystals have been performed along the {Σ} line to determine details of the band structure near the valence band maximum (VBM). Three bands are observed between VBM and 1 eV binding energy, instead of the two observed for a positive energy gap semiconductor CdTe. Their energy separations and positions relative to the Fermi energy are investigated at the {Γ} point and at slightly off-normal emission, applying room and low temperature of 40 K. In contrast to the heavily debated results of HgSe [K.-U. Gawlik et al., Phys. Rev. Lett. 78, 3165 (1997)] the clear observations for HgTe are consistent with the model of an inverted band structure, reflecting a semiconductor with a negative band gap.