Ideal PN photodiode using doping controlled WSe2–MoSe2 lateral heterostructure†
bd
and
Woo Jong
Yu
*a
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 VDS of 0 V to approximately −10 V) and enhances the photocurrent by the high built-in potential at the PN depletion layer (VOC = 0.52 V). Thus, our device exhibits a high Ilight/Idark 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.
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