Paolo Paletti’s demonstration of two-dimensional Esaki tunnel junctions is published in Nature Partner Journal 2D Materials and Applications. This work proves experimentally that p-n tunnel junctions can be formed using ions in polymers over transistor channels without the need for lateral ion positioning gates. This is part of an effort to explore new electron device functionality enabled by ions in semiconductors, including low-voltage transistors, neuromorphic devices, analog memory, and selectors.