Two-dimensional semimetal in HgTe-based quantum wells with surface orientation (100)

A 2D semimetal has been observed in 20 nm HgTe quantum wells with (100) surface orientation. At the charge neutrality point the hole and electron density were determined as N s = P s ≈ 1.2 × 10 10 cm − 2 and the band overlap was estimated at 1–1.5 meV. This observation confirms that a semimetallic state is a universal property of wide HgTe-based quantum wells with an inverted energy band structure independently of surface orientation. Energy band structure calculation shows that the strain caused by the lattice mismatch of HgTe and CdTe plays a crucial role in the formation of the conduction and valence band overlap. We show that in the investigated semimetal the ratio of the hole density to the electron density P s / N s may change from 1 up to about 102.