InAs/InAsSb type-II strained-layer superlattices for mid-infrared LEDs

InAs/InAsSb type-II strained-layer superlattice (SLS) and multiple quantum well (MQW) structures have been studied for their suitability in the active region of mid-infrared LEDs operating at room temperature. A series of InAs/InAs1-xSbx superlattices with low antimony content (x = 3.8-13.5%) were grown by MBE on InAs substrates and characterised using x-ray diffraction and photoluminescence (PL). The 4 K PL spectra of these samples exhibit the expected peak shift to longer wavelength and a reduction in intensity as the Sb content is increased. Band structure simulations highlight the effects of changing the antimony content and the layer thicknesses, to tailor the overlap of the electron and hole wavefunctions and maximise the radiative recombination rate. Analysis of the temperature dependence of the PL emission spectra enabled the extraction of quenching energies that demonstrate some suppression of Auger recombination in both the MQW and SLS structures. The MQW samples exhibit a changeover in the dominant radiative recombination process above similar to 100 K associated with thermal emission of holes into the InAs barriers; this behaviour was not observed in the SLS samples. These SLS structures have the potential for use as the active region in room temperature mid-infrared LEDs.