k·pmodel for the energy dispersions and absorption spectra of InAs/GaSb type-II superlattices

Abstract

We have fitted the k · p model derived recently by one of the authors [Klipstein, Phys. Rev. B 81, 235314 (2010)] to experimentally measured photoabsorption spectra at 77 and 300 K for representative InAs/GaSb superlattices with band-gap wavelengths between 4.3 and 10.5 μm. The model is able to reproduce the main features of the absorption spectra, including a strong peak from the zone boundary HH 2 → E 1 transition. We have also used the same model to predict the band-gap wavelengths of over 30 more superlattices, measured by photoluminescence spectroscopy. The maximum error is 0.6 μm, which corresponds to an uncertainty of less than 0.4 ML in layer width. This is comparable with the experimental uncertainty in layer widths, determined by in situ beam-flux measurements in the growth reactor. By eliminating all terms from the Hamiltonian, the energy contribution of which is less than the error due to the uncertainty in layer widths, the number of unknown fitting parameters has been reduced to six: two Luttinger parameters, three interface parameters, and the valence band offset. The remaining four Luttinger parameters are not independent and are determined from the two independent ones. Our set of Luttinger parameters is close to that reported by Lawaetz [Phys. Rev. B 4, 3460 (1971)], with a maximum deviation in any parameter of 0.6. The interface parameters are diagonal and have values of D S = 3 eVÅ, D X = 1.3 eVÅ, and D Z = 1.1 eVÅ at 77 K. The off-diagonal interface parameters α and β are too small to be fitted with any accuracy and have negligible effect on the unpolarized photoabsorption spectra. We also propose values for the room-temperature Luttinger and interface parameters. The fitted unstrained InAs/GaSb band overlap is 0.142 eV.

Effect of microscopic interface asymmetry on optical properties of short-period InAs/GaSb type-II superlattices

“…The presence of such two different interfaces gives rise to the microscopic interface asymmetry (MIA) which has a great influence on electronic and optical properties of InAs/GaSb type-II SLs [16]. Recently, the MIA effect on the electronic and optical properties of InAs/GaSb type-II SLs has been investigated using the k · p method [17,18]. The authors in these works incorporated the MIA effect into the k · p model by adding actual interface layers with thickness of about 0.5 monolayer (ML, 1 ML ≃ 3Å)…”

“…between InAs and GaSb layers [17] or by introducing delta-function-like interface terms with reduced parameters fitted to experimental photoabsorption spectra [18]. Here, we include the MIA effect in the k·p model by considering a short-range interface potential with delta-function form.…”

“…the first set consists of six SL samples with the InAs layer width varying from13,16,18,20,22 to 26Å and a constant GaSb layer 27Å; and the second set consists of five SL samples with the GaSb layer width varying from15,18,21,24, to 27Å and a constant InAs layer width of 26Å. We use the fitted value of H t (InSb) = 0.7 eV to calculate the band-gaps of these SL samples.…”

InAs/GaSb Type-II Superlattice Detectors

“…For example, Flatté et al have undertaken extensive theoretical modeling of the band structure of superlattices [27][28][29], including investigation of electronic structure of dopants [30]. Features of T2SL photoabsorption spectra and optical properties of T2SL detectors were studied by Livneh et al [31] and Qiao et al [32], respectively, using k ⋅ p tight-binding model [33]. Empirical pseudopotential method, in its canonical shape [34][35][36] and four-component variation that includes interface layers [37], was successfully utilized for the heterojunction design of T2SL devices.…”

Long Wave Infrared Type II Superlattice Focal Plane Array Detector

“…The simulation is based on a k · p treatment and optical transfer matrix (OTM) calculation recently reported elsewhere 7 . While the OTM technique is fairly standard, the k · p treatment contains a number of innovations 8 . This treatment leads to a reduced number of fitting parameters compared to other approaches, namely two independent Luttinger parameters (of InAs), three interface parameters, the valence band offset and a parameter close to unity that is related to the interband momentum matrix element.…”