INVESTIGATION OF MOLECULAR-BEAM EPITAXIALLY GROWN INAS/(IN,GA)SB STRAINED-LAYER SUPERLATTICES

We report on an investigation into the molecular-beam epitaxial growth and characterization of InAs/InxGa1-xSb (0 less-than-or-equal-to x less-than-or-equal-to 0.4) heterojunctions and strained-layer superlattices (SLS) for long-wavelength infrared detector applications. All structures have been grown on GaSb(100) substrates with period thicknesses of the SLS in the range 25-180 angstrom. Interface properties of single heterojunction structures have been characterized by x-ray photoelectron spectroscopy and secondary-ion mass spectroscopy depth profiles, and structural properties of the SLS have been assessed by transmission electron microscopy and x-ray diffraction analysis. For growth at an optimal temperature (390-degrees-C) the SLS are of high structural quality, with no evidence of compound formation at either (GaSb/InAs, InAs/GaSb) interface, or of post-growth interdiffusion. However, significant levels of As (7%) are found to be present in nominally grown InxGa1-xSb layers, resulting from incorporation from background. Fourier transform infrared absorption spectra of SLS samples have shown absorption thresholds out of 19-mu-m.