A k.p model of InAs/GaSb type II superlattice infrared detectors

作者：Klipstein P C^*; Livneh Y; Klin O; Grossman S; Snapi N; Glozman A; Weiss E

来源：Infrared Physics & Technology, 2013, 59: 53-59.

DOI：10.1016/j.infrared.2012.12.009

• Infrared detector
• pBp detector
• Type II superlattice
• InAs/GaSb superlattice
• Kane model
• k.p theory

We present and justify the TVK8 envelope function Hamiltonian for superlattice structures, which is a Kane-like Hamiltonian with a small number of fitting parameters [P.C. Klipstein, Phys. Rev. B 81 (2010) 235314]. In order to predict the bandgaps of type II InAs/GaSb superlattices in which the layer widths are known with a typical uncertainty of 0.2 monolayers (ML), it requires careful fitting of two Luttinger parameters, three interface parameters and the valence band offset. All other parameters, namely standard bandgaps, deformation potentials, electron masses and compliance coefficients, may be found in the literature. We have used the model to calculate the 77 K absorption spectra of representative MWIR and LWIR superlattices in which the layer widths have been determined by in situ beam flux measurements in the MBE reactor. By a comparison with the experimentally measured spectra, a unique set of the six fitting parameters has been determined. Our Luttinger parameters and band offset are close to those deduced by other workers. Using the same set of parameters we have then predicted the bandgaps in more than 30 superlattices with measured bandgap wavelengths in the range 4.3-12 mu m. The agreement is very good and is limited by the experimental uncertainty in the layer widths. This is typically 0.2 ML with a maximum value of 0.4 ML The model also reproduces the main features of the absorption spectrum, including the form and energy of the strong peak from zone boundary HH2 -> E-1 transitions, and the value of the bandgap blue shift when the GaSb thickness is increased. We use the modeled absorption spectra to calculate the spectral response of two pB(p)p barrier detectors with cut-off wavelengths in the MWIR and LWIR, respectively. We find that there is virtually no difference if the experimentally measured absorption spectra are used instead. This shows that the complete detector response can be predicted using only the superlattice period and bandgap as input parameters, together with the optical widths of the layers in the detector structure.

• 出版日期2013-7