A heterojunction diode is provided, including first and second semiconductor layers made of III-N material, the layers being superposed to form a two-dimensional electron gas; an anode and a cathode that are selectively electrically connected to each other by the electron gas; a third semiconductor layer positioned under the gas; a p-doped first semiconductor element contacting the anode the third layer, and forming a separation between the anode and the third layer; and an n-doped second semiconductor element contacting the cathode and the third layer, and forming a separation between the cathode and the third layer, the third layer and the first and second elements forming a p-i-n diode.