AlxIn1-xAsySb1-y alloys lattice matched to InAs with an Al content Lip to x = 0.25 have been grown by molecular beam epitaxy on InAs (001) substrates and studied by double-crystal X-ray diffraction, scanning electron microscopy and photoluminescence (PL) spectroscopy. Thermodynamic stability of these alloys at typical MBE temperatures has been revised. It has been found that AlInAsSb alloys with x ∼ 0.15, grown at temperatures below 470 ° C, exhibit spinodal decomposition in good agreement with the calculated chemical instability gap boundary. However, the alloys with x ∼ 0.2 grown at higher temperature (above 500 ° C) have exhibited no decomposition features and demonstrate bright PL at 80 K. © 2005 Published by Elsevier B.V.