Accurate Extraction of Schottky Barrier Height and Universality of Fermi Level De-Pinning of van der Waals Contacts

摘要

Due to Fermi level pinning (FLP), metal-semiconductor contact interfaces result in a Schottky barrier height (SBH), which is usually difficult to tune. This makes it challenging to efficiently inject both electrons and holes using the same metal-an essential requirement for several applications, including light-emitting devices and complementary logic. Interestingly, modulating the SBH in the Schottky-Mott limit of de-pinned van der Waals (vdW) contacts becomes possible. However, accurate extraction of the SBH is essential to exploit such contacts to their full potential. In this study a simple technique is proposed to accurately estimate the SBH at the vdW contact interfaces by circumventing several ambiguities associated with SBH extraction. Using this technique on several vdW contacts, including metallic 2H-TaSe2, semi-metallic graphene, and degenerately doped semiconducting SnSe2, it is demonstrated that vdW contacts exhibit a universal de-pinned nature. Superior ambipolar carrier injection properties of vdW contacts are demonstrated (with Au contact as a reference) in two applications, namely, a) pulsed electroluminescence from monolayer WS2 using few-layer graphene (FLG) contact, and b) efficient carrier injection to WS2 and WSe2 channels in both n-type and p-type field effect transistor modes using 2H-TaSe2 contact.