ALBERT

Description: We present an experimental investigation of the temperature dependence of the TO-phonon mode frequencies for the HgTe-based II-VI semiconductor solid solutions. In the case of the ternary Hg 0.9 Zn 0.1 Te solid solution was shown a discontinuity in the temperature dependence of the HgTe-like T 0 -mode and of the ZnTe-like T 1 -mode, similar to the Hg 0.85 Cd 0.15 Te system [Sheregii et al. , Phys. Rev. Lett. 102 , 045504 (2009)]. A generalization of the theoretical temperature shift of the phonon mode frequency as analytic equation is derived that includes both the anharmonic contribution and the electron-phonon e-p interaction which in this case is returnable—the electron subsystem effect on the phonon one. Data show that our equation satisfactorily describes the temperature shift of both Hg 0.85 Cd 0.15 Te and Hg 0.90 Zn 0.10 Te containing Dirac point ( E g ≡ Γ 6 – Γ 8  = 0) although one of the two constants describing the anharmonic shift of the HgTe-like mode should be positive what is abnormal too. In the case of the Hg 0.80 Cd 0.20 Te and Hg 0.763 Zn 0.237 Te solid solution, the role of the returnable e-p contribution is negligible but a positive temperature shift for the HgTe-like modes occurs. This result does not allow to explain the positive temperature shift of these modes merely by the contribution of the ( e-p ) interaction. Indeed, the relativistic contribution to the chemical bonds induces an abnormal temperature shift of the electron states in Hg-based semiconductors—the effect is expected since the Hg d spin-orbit split contribution to chemical bonds may lead to an abnormal temperature shift of the HgTe-like modes.