We report here the growth by pulsed laser deposition and characterization of metastable disordered Ti1-xGaxN alloy thin films on Al2O3(0001) substrates. X-ray diffraction and x-ray-absorption fine-structure analyses showed that the films contained a single rocksaltlike atomic structure for 0≤ x≪0.45, a single wurtzite-like structure for 0.75≤x≤1, and a mixture of both structures for 0.45≤x≪0.75. Over most of the composition range, the alloy films were predominantly amorphous with some fraction of nanocrystalline material present. Electrical conductivity measurements showed that the structural transition near x≈0.5 is accompanied by a metal–insulator transition. This study provides an increased understanding of the TiN–GaN pseudobinary phase field, which has potential technological implications for metallic contacts to GaN devices. © 1998 American Institute of Physics.