Electronic Structure and Luminescence Processes in In1−xGaxP Alloys

The conduction-band structure of In1−xGaxP has been studied by cathodoluminescence (CL) and photoluminescence (PL). An accurate determination of the direct energy gap (± 10 meV) as a function of alloy composition (Δx = ± 0.025) is achieved by the simultaneous electron probe microanalysis of alloy composition and spectral measurements of the CL excited by the microprobe electron beam. Similar measurements in InP, GaAs, and GaAs1−xPx, as well as absorption edge measurements and the temperature dependence of the PL spectrum, indicate that essentially free-carrier recombination is observed in the PL and CL measurements of lightly n-type In1−xGaxP at 300 °K. These results indicate that the ``cross over'' between the direct and indirect conduction-band minima occurs at the composition x = 0.74 and energy gap = 2.26 eV.