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We report here the electronic band structure of nanostructure type II superlattice (SL) InAs(d1 = 21 A)/GaSb(d2 = 24 A) performed in the envelope function formalism. We calculated the energy E(d1), E(kz), E(kp) and the effective mass in the direction of growth kz and in plane kp of the SL. When the temperature increases, the band gap Eg decreases and the corresponding cutoff wavelength λc increases. We interpreted photoluminescence and transport measurements of Haugan et al. with an agreement in the calculated gaps. The computed density of states and Fermi energy position indicated that the sample is a p type semiconductor with a transition from bi-dimensional to tri-dimensional conductivity near 20 K. This sample is medium infrared detector (3.92 μm

We investigated, theoretically, the electronic band structures, transport and magneto-transport properties of In0.53Ga0.47As(d1 = 10 nm)/InP(d2 = 5 nm) lattice matched superlattice (SL) at 1.7 K. These studies were performed in the envelope function formalism with effects of well thickness d1. The SL has a direct band gap of 849 meV and the cut-off wavelength of 1.46 μm indicates that it can be used as a short infrared detector. The computed density of states and position of Fermi level, predict that this sample is a quasi two-dimensional system and exhibits n type conductivity. We have interpreted the oscillations in the magneto-resistance observed by Pusep et al. in this superlattice. These results were compared and discussed with the available data in the literature.

We have used the envelope function formalism (EFF) to investigate the bands structure, energy subbands and carrier's effective mass in the growth direction and in-plan of InAs(d1 = 160 A)/GaSb(d2 = 105 A) semimetallic superlattice. The photodetector parameters like optical band-gap, Eg, cut-off frequency, |fc|, and in-plan electron effective mass, m∗E1, were calculated as a function of d1 and/or d2 and temperature T. Eg(R = d1/d2) indicates that the semiconductor-to-semimetal transition goes to lower R when T increases. The range of 11.6 ≤|fc(THz)|≤ 23.8, demonstrates that this sample can be used as a terahertz (THz) detector. For T ≤ 141 K, our results agree with the available experimental data. Using the Boltzmann magnetic-field-dependent Hall coefficient and the magnetoresistance results of D. M. Symons et al., we have deduced the SL electronic parameters. At 141 K, the p to n-type conductivity transition was observed at B0 = 32 T. The Fermi level, EF = 515 meV, reveal a p-type conductivity at 300 K.

We have investigated in the bands structure and the effective mass, respectively, along the growth axis and in the plane of InAs (d1=48.5Å)/GaSb(d2=21.5Å) type II superlattice (SL), performed in the envelop function formalism. We studied the semiconductor to semimetal transition and the evolutions of the optical band gap, Eg(Γ), as a function of d1, the valence band offset Λ and the temperature. In the range of 4.2–300 K, the corresponding cutoff wavelength ranging from 7.9 to 12.6 µm, which demonstrates that this sample can be used as a long wavelength infrared detector. The position of the Fermi level, EF = 512 meV, and the computed density of state indicates that this sample is a quasi-two-dimensional system and exhibits n type conductivity. Further, we calculated the transport scattering time and the velocity of electrons on the Fermi surface. These results were compared and discussed with the available data in the literature.

We report here the electronic band structures of symmetric type I GaAs ( $$d_{1}= 2.83$$ nm)/AlAs ( $$d_{2}= 2.83$$ nm) superlattice as a function of the well thickness $$d_{1}$$ and the effect of the valence band offset $$\Lambda $$ , the ratio $$d_{2}$$ / $$d_{1}$$ , and the temperature on the band gap energy, performed in the envelop function formalism. These results are compared and discussed with the experimental measurements reported in the literature.

We report here the theoretical calculations of band structures E(d 1), E(k z , k p ) and effective mass along the growth axis and in the plane of GaAs/Al x Ga1−x As superlattices, in the envelope function formalism. The effect of valence band offset, well thickness and temperature on the band structures, has been also studied. Our results show that a transition from indirect to direct band gap in (GaAs) m /(AlAs)4 takes place between m = 5 and 6 monolayers at room temperature. Samples (GaAs)9/(AlAs)4 and GaAs(d 1 = 10 nm)/Al0.15Ga0.85As(d 2 = 15 nm) have a direct band gap of 1.747 eV at room temperature and 1.546 eV at T = 30 mK, respectively. Their corresponding cutoff wavelengths are located in the near infrared region. We have interpreted the photoluminescence measurements of Ledentsov et al. in GaAs(d 1 = 2.52 nm)/AlAs (d 1 = 1.16 nm) and the oscillations in the magnetoresistance observed by Kawamura et al. in GaAs/Al0.15Ga0.85As superlattice. In the later, the existence of discrete quantized levels along the growth direction z indicates extremely low interactions between adjacent wells leading to the use in parallel transport. The position of Fermi level predicts that this sample exhibits n-type conductivity. These results were compared and discussed with the available data in the literature and can be used as a guide for the design of infrared nanostructured detectors.

The present work is devoted to the study of band structure and band gap in symmetric InAs (d 1 = 25 A)/GaSb (d 2 = 25 A) type II superlattice. Our calculations were performed in the envelope function formalism with the valence band offset Λ = 570 meV. We discussed the semiconductor to semimetal transition and the evolutions of the fundamental band gap, E g (Γ), as a function of d 1, Λ and the temperature. This study suggests that a wide range of wavelength can be reached by adjusting d 1. In addition, E g (Γ, T) decreases from 288.7 to 230 meV in the range of 4.2–300 K, corresponding to the cutoff wavelength ranging from 4.3 to 5.4 µm. These latter results explain the recent experimental ones realized by C. Cervera et al. for our Λ = 588 meV.

We have investigated the band structure E(d = d 1 + d 2), E(k z) and E(k p), respectively, as a function of the SL period, d, in the growth direction and in plan of InAs(d 1 = 160 A)/GaSb(d 2 = 105 A) type II superlattice, performed in the envelope function formalism with the valence band offset, Λ, of 510 meV at 4.2 K. For the ratio d 1/d 2 = 1.52, d and Λ dependence of the SL energy band gap show that the semiconductor-to-semimetal transition takes place at d c = 173 A and Λ c = 463 meV. Therefore, this sample is semimetallic. The position of the Fermi level, E F = 500.2 meV, indicates n type conductivity. The spectra of energy, E(k z, k p), show a negative band gap of −48.3 meV. The cutoff wavelength |λ c| = 25.7 µm indicates that this sample can be used as a far-infrared detector. Further, we have interpreted the minima of the magnetoresistance oscillations, Shubnikov–de Haas effect, observed by D. M. Symons et al.