Gate-Tunable WSe/SnSe Backward Diode with Ultrahigh-Reverse Rectification Ratio.

Backward diodes conduct more efficiently in the reverse bias than in the forward bias, providing superior high-frequency response, temperature stability, radiation hardness, and 1/f noise performance than a conventional diode conducting in the forward direction. Here, we demonstrate a van der Waals material-based backward diode by exploiting the giant staggered band offsets of WSe/SnSe vertical heterojunction. The diode exhibits an ultrahigh-reverse rectification ratio (R) of ∼2.1 × 10, and the same is maintained up to an unusually large bias of 1.5 V-outperforming existing backward diode reports using conventional bulk semiconductors as well as one- and two-dimensional materials by more than an order of magnitude while maintaining an impressive curvature coefficient (γ) of ∼37 V. The transport mechanism in the diode is shown to be efficiently tunable by external gate and drain bias, as well as by the thickness of the WSe layer and the type of metal contacts used. These results pave the way for practical electronic circuit applications using two-dimensional materials and their heterojunctions.