The growth by molecular beam epitaxy of In0.74Ga0.26As is investigated because of its importance as a PV converter for a variety low temperature TPV system configurations. In this work, a linearly graded buffer layer is used to grow high quality In0.74Ga0.26As layers on a lattice mismatched InP substrate. The thickness of the buffer layer and the substrate temperature during the growth of the buffer and active layers were varied in order to optimize the active layer material quality. The resultingp+−i−n+epitaxial layers were compared using double crystal x‐ray diffraction, spectral response, and current‐voltage measurements. A more conventional PV cell structure was also evaluated using current‐voltage measurements. ©1996 American Institute of Physics.