The invention relates to an electronic component with a high-electron-mobility heterojunction. The component includes a superposition of a first semiconductor layer and of a second semiconductor layer, to form an electron-gas layer in proximity to the interface between the first and second semiconductor layers, and first and second conductive metal electrode contacts formed on said second semiconductor layer plumb with the electron-gas layer. At least one of the first and second metal contacts has a contact length L such that L≤1.5*√(ρc/R2 Deg), where ρc is the specific resistance of the metal contact with the electron-gas layer at 425 K and R2 Deg is the sheet resistance in the electron-gas layer at 425 K.