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 Sigma 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 Gamma 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 nl., 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.