Determination of the direct to indirect bandgap transition composition in AlxIn1−xP

AlxIn1−xP semiconductor alloys grown by metalorganic chemical vapor deposition on InGaAs graded buffer layers with varied aluminum compositions that span the transition from a direct to indirect semiconductor alloy are explored. The direct and indirect band gap transitions are observed in a single AlxIn1−xP sample with 40.8% allowing for a precise determination of the direct-indirect cross-over composition, xc. The direct and indirect nature of observed luminescence peaks is verified using time-resolved photoluminescence. At low temperatures, xc is determined to be 40.5% at a corresponding direct band gap energy of 2.34 eV.