Esaki tunnel diodes based on vertical Si-Ge nanowire heterojunctions

High performance Esaki tunnel diodes [L. Esaki, Phys. Rev. 109, 603 (1958)] based on small-diameter Ge/Si core/shell nanowires vertically grown on Si substrates are demonstrated. The devices exhibit pronounced negative differential resistance with peak-to-valley current ratio of 2.75, high peak current density of 2.4 kA/cm2, and high tunneling current density of 237 kA/cm2 at 1 V reverse bias, all obtained at room temperature. The peak current is found to increase with temperature and the data can be well explained with a band-to-band tunneling model. These results suggest that Si-Ge heterojunction with low defect density can be obtained for device applications such as tunnel diodes and tunnel field-effect transistors.