We report on novel Ir–Al/n‐GaAs Schottky contact systems based on sequentially evaporated Ir–Al multilayers which enable us to control the barrier height at the interface with annealing temperature. Auger depth profiling and Rutherford backscattering methods were applied to analyze the Ir–Al composition and the interfacial reaction stability. An increase of the barrier height with annealing temperature has been indicated for all the Schottky contact systems. Barrier heights as high as 0.95 V were measured for annealed Schottky diodes with the first aluminum or very thin iridium interfacial layer. A model of the barrier height enhancement based on a solid phase epitaxy of a graded AlxGa1−xAs layer at the interface at elevated annealing temperatures was considered to explain the electrical properties of the contacts. The model contributions to the formation of a metal/AlxGa1−xAs/GaAs heterojunction diodes with required barrier height and thermal stability are discussed.