The ternary semiconductor InxGa1−xAs has been a key component of current thermophotovoltaic energy converters. These studies indicate that the bandgap of the epitaxial films, that are lattice‐matched to InP, show varying degrees of ordering of the metal sublattice depending upon growth temperature. The bandgap of partially ordered films is lowered by as much as 75 meV. The transport of carriers in ordered films is dominated by domain trapping. ©1996 American Institute of Physics.