Optical And Electrical Properties Of Type Iiihgte/Hg1-Xcdxte Heterostructures

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 - El and L1 - El intersubband transition energies of semiconducting HgTe/Hg1-xCdxTe 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: n is also temperature dependent according to d Lambda /dT = -0.40 +/- 0.04 meV/K; the heavy hole effective mass has a significant temperature dependence; and the energy gap E-g(HgTe, 300 K)= -160 +/- 5 meV which is appreciably lower than the extrapolated values found in the literature.Both n and p type modulation doped HgTe/Hg-1_xCdxTe quantum wells, QW, have been investigated. Magnetotransport measurements of n type QWs show very pronounced Shubnikov-de Haas, SdH, oscillations and well developed quantum Hall plateaus for temperatures up to approximately 60 K. The SdH oscillations for asymmetric n type modulation doped structures display spin splitting at zero magnetic field, whereas this is not the case for similar symmetric structures. This effect increases with increasing quantum well width and preliminary calculations qualitatively agree with these results which we tentatively ascribe to Rashba spin splitting.