Ambipolar Charge Transport in Degenerately Doped Transition Metal Dichalcogenides

A family of layered transition metal dichalcogenides (TMDs) is a promising candidate for nanoelectronics and neuromorphic computing owing to their excellent gate-controlled tunability in charge transport. However, despite an explosive amount of research activities, the interplay between intrinsic and extrinsic impurities as well as the effect of surrounding dielectric medium often makes it challenging to further understand the origin of their charge transport characteristics. Here, we report the ambipolar behavior in extrinsically doped TMD based field-effect transistors, abruptly appearing when being thinned down, and further demonstrate its modulation by inserting an interlayer between the substrate and semiconducting channel. When doped TMDs directly contacted with a disordered gate dielectric, ambipolar transport occurs, and it can be understood by the Poole-Frenkel emission and space charge limited current models. The present result indicates that the transport mechanism indicated as the bulk-limited current is another one to interpret and predict further functionalities of ambipolar behavior.