Ideal PN photodiode using doping controlled WSe2–MoSe2 lateral heterostructure

Abstract

As the tight contact interface of the lateral PN junction enables high responsivity, specific detectivity, and fast response speed, atomic-scale two-dimensional (2D) lateral PN heterostructures are emerging as viable alternatives to silicon-based photodiodes. The optical properties of the current 2D heterostructures depend entirely on the intrinsic properties of 2D materials, which can be greatly improved by forming an ideal PN diode via the doping control of 2D heterostructures. In this study, we propose a high-performance photodiode using a doping-controlled WSe₂–MoSe₂ PN heterojunction. During the synthesis, the low chemical reactivity of Nb₂O₅ with WO₃ as compared to MoO₃ enables sequential growth and prevents niobium (Nb) doping during MoSe₂ growth at low temperatures. Conversely, in the WSe₂ growth at high temperatures, tungsten (W) to Nb is selectively substituted, resulting in the lateral heterostructure of Nb-doped WSe₂–MoSe₂. The Nb atoms in WSe₂ change the WSe₂ type from ambipolar to p-type dominant. Together with intrinsically n-type MoSe₂, Nb-doped WSe₂ forms a lateral PN heterostructure with a near-unity ideality factor (1.3) and a high forward/reverse current ratio of 10⁴. Our ideal 2D PN photodiode effectively suppresses the dark current in the reverse bias region (∼100 fA at an overall V_DS of 0 V to approximately −10 V) and enhances the photocurrent by the high built-in potential at the PN depletion layer (V_OC = 0.52 V). Thus, our device exhibits a high I_light/I_dark ratio (10⁵) and a corresponding ultra-high detectivity (5.78 × 10¹⁵ Jones), which are approximately 100 times higher than those of reported lateral 2D PN heterostructure photodiodes. These outstanding performances show that the doping-controlled transition metal dichalcogenide PN heterostructures are promising candidates for next-generation optoelectronics.