Interstitial copper-doped edge contact for n-type carrier transport in black phosphorus

Black phosphorus (BP) has been shown as a promising two-dimensional (2D) material for electronic devices owing to its high carrier mobility. To realize complementary electronic circuits with 2D materials, it is important to fabricate both n-type and p-type transistors with the same channel material. By engineering the contact region with copper (Cu)-doped BP, here we demonstrate an n-type carrier transport in BP field-effect transistors (FETs), which usually exhibit strongly p-type characteristics. Cu metal atoms are found to severely penetrate into the BP flakes, which forms interstitial Cu (Cu-int)-doped edge contact and facilitates the electron transport in BP. Our BP FETs in back-gated configuration exhibit n-type dominant characteristics with a high electron mobility of similar to 138 cm(2) V-1 s(-1) at room temperature. The Schottky barrier height for electrons is relatively low because of the edge contact between Cu-int-doped BP and pristine BP channel. The contact doping of BP by highly mobile Cu atoms gives rise to n-type transport property of BP FETs. Furthermore, we demonstrate a p-n junction on the same BP flake with asymmetric contact. This strategy on contact engineering can be further extended to other 2D materials.