Conduction- and Valence-Band Energies in Bulk InAs1−xSbx and Type II InAs1−xSbx/InAs Strained-Layer Superlattices

The energy gaps were studied in two types of structures: unrelaxed bulk InAs1−xSbx layers with x = 0.2 to 0.46 grown on metamorphic buffers and type II InAs1−xSbx/InAs strained-layer superlattices (SLS) with x = 0.225 to 0.296 in the temperature range from T = 13 K to 300 K. All structures were grown on GaSb substrates. The longest wavelength of photoluminescence (PL) at low temperatures was observed from bulk InAs0.56Sb0.44 with a peak at 10.3 μm and full-width at half-maximum (FWHM) of 11 meV. The PL data for the bulk InAs1−xSbx materials of various compositions imply an energy gap bowing parameter of 0.87 eV. A low-temperature PL peak at 9.1 μm with FWHM of 13 meV was observed for InAs0.704Sb0.296/InAs SLS. The PL spectrum of InAs0.775Sb0.225/InAs SLS under pulsed excitation revealed a second peak associated with recombination of electrons in the three-dimensional (3D) continuum with holes in the InAs0.775Sb0.225. This experiment determined the conduction-band offset in the InAs0.775Sb0.225/InAs SLS. The energies of the conduction and valence bands in unstrained InAs1−xSbx and their bowing with respect to the Sb composition are discussed.