Optical and electrical properties of type III HgTe/Hg 1-x Cd x Te heterostructures

Abstract

By means of an optical investigation involving the envelope function approximation using the full 8 X 8 Kane Hamiltonian, it has been demonstrated that the valence band is primarily responsible for the separation between the H1- E1 and L1-E1 intersubband transition energies of semiconducting HgTe/Hg<SUB>1-x</SUB>Cd<SUB>x</SUB>Te superlattices with a normal band structure. This results in an unequivocal determination of the valence band offset between HgTe and CdTe, (Lambda) , which is 570 +/- 60 meV at 5 K for both the (001) and the (112)B orientations. In order to correctly predict the temperature dependence of both intersubband transition energies, the following is required: (Lambda) is also temperature dependent according to d(Lambda) /dT equals -0.40 +/- 0.04 meV/K; the heavy hole effective mass has a significant temperature dependence; and the energy gap E<SUB>g</SUB>(HgTe, 300 K)equals -160 +/- meV which is appreciably lower than the extrapolated values found in the literature.