A heterostructure device includes a semiconductor multi-layer structure that has a first region, a second region and a third region. The first region is coupled to a source electrode and the second region is coupled to a drain electrode. The third region is disposed between the first region and the second region. The third region provides a switchable electrically conductive pathway from the source electrode to the drain electrode. The third region includes iodine ions. A system includes a heterostructure field effect transistor that includes the device.