Photo-excited carrier density in short-period InAs/GaSb type-II superlattice

We present a systematic theoretical study on optical properties of short-period InAs/GaSb type-II superlattices (SLs) which can serve for Mid-Infrared (MIR) detection. From the energy dispersion relation for the electron derived from using the standard Kronig-Penney model we calculate the electron-minibands structure in InAs layer and the hole-minibands structure in GaSb layer of such SLs. The obtained band-gap energies are in line with those realized experimentally. On the basis of the mass-balances equations derived from the Boltzmann equation, at the same time considering the polarization direction of the infrared irradiation vertical to the growth direction of the material, we develop an approach to calculate the Fermi level and photo-excited carrier density in the corresponding SL systems. The dependence of photo-conductivity in InAs/GaSb type-II SLs on temperature and well-widths are examined. This study is pertinent to the application of InAs/GaSb type-II SLs as uncooled MIR photodetectors. © 2009 SPIE.