Optical measurements of electronic bandstructure in AlGaInP alloys grown by gas source molecular beam epitaxy

A series of bulk (AlyGa1−y)0.52In0.48P epilayers, covering the full range of compositions from y=0 to y=1, have been grown lattice matched on GaAs substrates by gas source molecular beam epitaxy. Double crystal x-ray diffraction, and low temperature photoluminescence (PL) and photoluminescence excitation (PLE) optical spectroscopy have been used to characterize the structures. PL and PLE data indicate the direct-to-indirect energy gap crossover composition to be near y∼0.55 for this alloy system. From PLE, the y dependence of the (5 K) lowest energy direct gap, EΓ–Γ, has been found to be 2.014+0.499y+0.16y2 eV. EΓ–Γ (5 K) for the indirect-gap ternary end-member Al0.52In0.48P is directly determined to be 2.685 eV.