Gate tunable 2D WSe2 Esaki diode by SiNx doping

Negative Differential Resistance (NDR) has recently been observed in van der Waals heterojunctions made of two-dimensional (2D) layered materials, evidencing Esaki tunneling diodes in vertical structures [1-5]. However, the lack of fundamental understanding on vertical tunneling mechanisms, interface quality, band off-set, etc. hinders their practical applications. On the other hand, extensive knowledge has been obtained on conventional lateral tunneling junctions [6]. Experimentally, although a number of sub-60mV/dec tunneling field-effect transistors (TFETs) have been demonstrated [7], many did not show a steep slope due to the wrong material choices, trap charges, and non-optimized device structures. In this paper, we focus on WSe
₂
, a 2D transition metal dichalcogenide (TMD) layered material whose bandgap is a function of its layer number. We demonstrate the first gate tunable Esaki diode with NDR in a WSe
₂
homojunction by combing strong n-type doping from a SiNx passivation layer [8] and a top gate controlled p-type region. Simulations are presented to compare with experimental measurements and to provide guidance to further improve tunneling efficiency.