Abstract
Ohmic contacts to n-GaAs formed by the heat treatment of In films have been investigated. The widely-accepted model for ohmic contact formation, involving the establishment of a heavily-doped layer, fails in this case because In is not a n-type dopant in GaAs. It is shown that the heat treatment results in the formation of a graded InxGa1−xAs (0≤x<1) heterojunction. This heterojunction is responsible for the ohmic behavior.