Cold Source Diodes With Sub-Unity Ideality Factor and Giant Negative Differential Resistance

Conventional Schottky diodes have a switching limit of ideality factor larger than unity due to the thermionic emission. In this work, cold source diodes (CSDs) using cold metals of monolayer 2H phase MX2(M = Nb, Ta; X = S, Se) as the injection source are proposed and investigated by first-principles quantum transport simulations. Different from the conventional Schottky diode, CSDs can break the ideality factor limit of unity and reach steep switching. Cold metals such as 2H MX2are metallic but have energy gaps around the Fermi level. Therefore, high-energy electrons can be effectively filtered and the leakage current is suppressed at off-state. It is shown that the ideality factor of CSDs can be smaller than 1 over eight decades with a minimum of 0.17. At the same time, giant negative differential resistance is realized in CSDs and the peak-to-valley ratio (PVR) can be over 106with a peak current over 100
$\mu \text{A}/\mu \text{m}$
.