Radiative Processes in Direct and Indirect Band Gap In1−xGaxP

Abstract

Using a new technique for measuring time‐resolved spectra, the radiative recombination processes have been studied in In_1−xGa_xP for compositions in the vicinity of the direct‐indirect band‐gap crossover point. Free‐to‐free, free‐to‐bound, and bound‐to‐bound (donor‐acceptor pair) transitions are shown to occur in Zn‐doped samples at various temperatures in both direct and indirect band‐gap materials close to the crossover composition. Time‐decay measurements of the donor‐acceptor pair recombination show the effect of the increased recombination transition rate as the lowest conduction‐band minimum changes from X to Γ. Optical‐absorption measurements have been used to determine the band gap for the Γ valley as a function of composition and temperature and to confirm the presence of free‐electron‐hole recombination. The measurements in this work support the direct‐indirect transition band gap of 2.17 eV at 300 °K determined from pressure experiments. The recombination probability B for direct band‐gap compositions of In_1−xGa_xP has been determined to be 7.5 × 10⁻¹⁰ cm³/sec at 300 °K and band gaps between 2 and 2.2 eV. In_1−xGa_xP near the direct‐indirect transition have a measured index of refraction of 3.46.