Multifunctional van der Waals Broken‐Gap Heterojunction

Abstract The finite energy band‐offset that appears between band structures of employed materials in a broken‐gap heterojunction exhibits several interesting phenomena. Here, by employing a black phosphorus (BP)/rhenium disulfide (ReS 2 ) heterojunction, the tunability of the BP work function ( Φ BP ) with variation in flake thickness is exploited in order to demonstrate that a BP‐based broken‐gap heterojunction can manifest diverse current‐transport characteristics such as gate tunable rectifying p–n junction diodes, Esaki diodes, backward‐rectifying diodes, and nonrectifying devices as a consequence of diverse band‐bending at the heterojunction. Diversity in band‐bending near heterojunction is attributed to change in the Fermi level difference (Δ) between BP and ReS 2 sides as a consequence of Φ BP modulation. No change in the current transport characteristics in several devices with fixed Δ also provides further evidence that current‐transport is substantially impacted by band‐bending at the heterojunction. Optoelectronic experiments on the Esaki diode and the p–n junction diode provide experimental evidence of band‐bending diversity. Additionally, the p + –n–p junction comprising BP (38 nm)/ReS 2 /BP(5.8 nm) demonstrates multifunctionality of binary and ternary inverters as well as exhibiting the behavior of a bipolar junction transistor with common‐emitter current gain up to 50.