Fabrication of the TTD. a, Schematic structure of the TTD and a symbol representing the emitter and detector. b, SEM image of the fabricated device c, STEM image of the epitaxial structure with the Au/Ti/Al2O3/p–GaN layers and the AlGaN MQW region. d, Selected area with red square STEM image and the corresponding EDS elemental mapping images for Ga (green), Al (brown) and Ti (yellow), respectively. Credit: Nature Electronics (2024). DOI: 10.1038/s41928-024-01142-y Two-terminal devices are electr...