Black phosphorus inverter devices enabled by in-situ aluminum surface modification

Two-dimensional black phosphorus (BP) generally exhibits a hole-dominated transport characteristic when configured as field-effect transistor devices. The effective control of charge carrier type and concentration is very crucial for the application of BP in complementary electronics. Herein, we report a facile and effective electron doping methodology on BP, through in situ surface modification with aluminum (Al). The electron mobility of few-layer BP is found to be largely enhanced to ∼ 10.6 cm2·V–1·s–1 by over 6 times after aluminum modification. In situ photoelectron spectroscopy characterization reveals the formation of Al–P covalent bond at the interface, which can also serve as local gate to tune the transport properties in BP layers. Finally, a spatially-controlled aluminum doping technique is employed to establish a p–n homojunction on a single BP flake, and hence to realize the complementary inverter devices, where the highest gain value of ∼ 33 is obtained.