In an example embodiment, a heterojunction device comprises a substrate, a multilayer structure disposed on the substrate. The multilayer structure has a first layer having a first semiconductor disposed on top of the substrate; a second layer has a second semiconductor is disposed on top of the first layer defining an interface between them. The second semiconductor differs from the first semiconductor such that a 2D Electron Gas forms adjacent to the interface. A first terminal couples to a first area of the interface between the first and second layers and a second terminal couples to a second area of the interface between the first and second layers; an electrically conducting channel comprises a metal or a region of the first layer with a higher defect density than another region of the first layer. The channel connects the second terminal and a region of the first layer such that electric charge can flow between them.