Correlation between band structure and magneto-transport properties in far-infrared detector superlattice

摘要

We report here carrier's magneto-transport properties and the band structure results for Ⅱ-Ⅳ semiconductors. HgTe is a zero gap semiconductor when it is sandwiched between CdTe layers to yield to a small gap HgTe/CdTe superlattice which is the key of an infrared detector. Our sample, grown by MBE, had a period d (100 layers) of 18 nm (HgTe) / 4.4 nm (CdTe). Calculations of the spectra of energy E(k_z) and E(k_p), respectively, in the direction of growth and in the plane of the superlattice were performed in the envelope function formalism. The angular dependence of the transverse magnetoresistance follows the two-dimensional (2D) behavior with Shubnikov-de Haas oscillations. At low temperature, the sample exhibits p type conductivity with a hole mobility of 900 cm~2/V.s. A reversal the sign of the weak-field Hall coefficient occurs at 25 K with an electron mobility of 3.10~4 cm~2/Vs. In intrinsic regim, the measured E_g ≈ 38 meV agrees with calculated E_g(Γ,300 K) = 34 meV which coincide with the Fermi level energy. The formalism used here predicts that this narrow gap sample is semi metallic, quasi-two-dimensional and far-infrared detector.