Tight-binding calculations of energy gaps in (001)-(InAs)n(InSb)m strained superlattices

Abstract

Tight-binding calculations of electronic structures for (001)-(InAs)n(InSb)m strained layer superlattices are presented. The dependences of the superlattice band gap on the band offsets between InAs and InSb are examined for three different types of biaxial strains. It is found that the band gap depends strongly on the band offset, and that for m=1 the ordering lowers the band gap with respect to the random alloy. A comparison with the photoluminescence data for the energy gaps of (n×1) strained-layer superlattices is discussed. In addition, the electronic structures of strained InAs quantum wells are calculated, and interpretations are provided for the observed type-I to type-II band alignment transition at n=5 in a quantum well formed by (n×1) strained layer superlattices and AlSb barriers. Changes of energy gaps with layer thicknesses in strained layer superlattices with n=m and n=8−m are also studied.

Microscopic theory of nanostructured semiconductor devices: beyond the envelope-function approximation

“…This is particularly true in SLs where there is mixing of direct and indirect gaps. ETB calculations have been carried out for group IV SLs such as Si/SiGe [119,166,167], Sn/Ge [168,169], for III-V based SLs such as GaAs/AlAs [170][171][172][173][174][175], InAs/GaSb [176][177][178], InAs/AlSb [83], InAs/InSb [179], GaSb/AlSb [180], GaAs/GaAsP [181,182], GaP/AlP [183], for II-VI SLs ZnSe/ZnTe [184], CdTe/HgTe [185][186][187][188], HgCdTe/CdTe [99,189], for mixed SLs made with III-V/IV semiconductors such as GaAs/Ge [190], AlAs/Ge [190], Si/GaP [191], or made with II-VI/IV semiconductors such as ZnS/Si [192], BeSe/Si [193], BeTe/Si [194], BeTe/Ge [194], BeTe/SiGe [194], ZnS/Ge [192], ZnSe/Ge [95,190] and for other SLs as Si/SiO 2 [195], EuS/PbS [196], EuTe/PbTe [196]. We should remember, however, that short-period SLs have also been investigated by ab initio methods [168,[197]…”

The electronic properties of the strained CdTe/ZnTe(001) superlattices

“…For all the reasons mentioned above, we have employed the sp 3 s * TB method, with inclusion of spin-orbit coupling and strain effects, to investigate the electronic properties of the strained CdTe/ZnTe(001) SLs. It is worth mentioning, here, that in the literature several attempts have been made to incorporate the strain effects within the TB Hamiltonian [6][7][8][9][10][11][12][13][14]. More specifically in the case of mismatched SLs, the biaxial strain results mainly in two structural distortions: (i) bond-length distortion and (ii) angular distortion.…”

“…On the other hand, the second distortion affects the bond-directional cosines (l, m, n) which make the p x , p y and p z orbitals asymmetrically contribute to the TB Hamilonian. As a consequence, in the presence of biaxial strain, the LH-HH degeneracy at the -point must be lifted [14] if the Hamiltonian is expressed in the Slater-Koster scheme [5] with the minimal sp 3 basis set and in neglect of spin-orbit interaction. A subsequent development of this model is the addition of an excited s * state to this latter basis set by Vögl et al [16].…”

Photoluminescence of InAs1−xSbx/AlSb single quantum wells: Transition from type-II to type-I band alignment

“…This band-gap reduction is attributed to the InAs/InSb lattice ordering in the context of the x-ray diffraction measurements and the tight binding calculation. 7 In addition, we use infrared photoluminescence ͑PL͒ 8 to demonstrate the desired type-I alignment for the lattice closely matched InAs 0.8 Sb 0.2 /AlSb system.…”