Broadly Tunable AlInAsSb Digital Alloys Grown on GaSb

AlxIn1-xAsySb1-y digital alloys lattice-matched to GaSb were grown within the miscibility gap by molecular beam epitaxy, with aluminum fractions ranging from 0% to 80%. Photoluminescence spectra from AlxIn1-xAsySb1-y films and from AlxIn1-xAsySb1-y/GaSb type-II superlattices were used to determine the direct bandgap and the band offsets as a function of the aluminum fraction. Varying the aluminum content tuned the direct bandgap from 0.25 eV (0% aluminum) to 1.24 eV (75% aluminum), corresponding to photon wavelengths from 5000 to 1000 nm, with the transition from direct-gap to indirect-gap occurring at similar to 1.18 eV (similar to 72% aluminum), or 1050 nm. This direct gap tuning range of 0.93 eV is the largest reported for a III-V alloy lattice-matched to a commercially available substrate. The broadly tunable bandgap and type-I band alignments of this lattice-matched quaternary make it attractive for advanced mid infrared and near-infrared detectors and sources.