Two-dimensional electron-hole system in HgTe-based quantum wells with surface orientation (112)

A two-dimensional electron-hole system has been shown to exist in 20 nm thick HgTe quantum wells (QWs) with the orientation (112). This finding proves that the semimetallic state is a universal property of wide HgTe-based quantum wells with an inverted energy band structure that is independent of surface orientation. Calculation of the energy band structure in these QWs shows that the strain caused by the lattice mismatch of HgTe and CdTe is likely to be a key reason for the formation of the overlap of the conduction and valence bands that leads to a semimetallic state. In the vicinity of the charge neutrality point (i.e., the point where the electron and hole densities are equal), the system is found to be in an insulating state with an anomalously weak power-law temperature dependence of the resistivity.