Demonstration of electric double layer p-i-n junction in WSe2

We demonstrate the first electric double layer p-i-n junction in the channel of a WSe2 field-effect transistor (FET). The measured current-voltage (I-V) characteristics have a nearly constant ideality factor over approximately three orders of magnitude in current. This is better than any prior report on WSe2. The formation technique has wide applicability across materials systems and is of particular interest for the formation of source-channel junctions in tunnel FETs in transition metal dichalcogenides (TMDs) [1]. The most ideal TMD p-n junctions formed to date have been achieved using buried gates under WSe2 by Ross [2], under MoS2 by Sutar [3], by charge transfer doping in MoS2 by Choi [4] and Li [5], and by EDL formation in MoTe2 by Xu [6]. The junction formation described in this paper does not require fabrication of additional field plates to position the ions.