The band structure and the double metal-insulator-metal phase transition in the conductivity of elastically strained zero-gap Cd x Hg1−x Te

Abstract

In the zero-gap CdxHg1−xTe semiconductor subjected to an axial elastic strain, a band gap is formed between the bottom of the conduction band and the top of the valence band. In the new state, the band structure is found to depend on the initial arrangement of the valence subbands, i.e., on the composition defined by the parameter x. At x < 0.135–0.140, the material becomes a semiconductor with an indirect band gap. If 0.140 < x < 160, the band of light holes at k = 0, Γ6, is found to be above the Γ8 band. As a result, the material becomes a direct-gap semiconductor, and a double “metal-semiconductor-metal” phase transition in conductivity occurs. In this case, as the strain is increased, the type of conductivity of the zero-gap semiconductor at low temperatures changes according to the sequence as follows: electron metallic conductivity-electron activation conductivity-hopping conductivity-hole metallic conductivity.