WS₂(RE)/Si₂(X)H co-doped heterojunctions for wide-spectrum and high-performance photodetections

A layered heterostructure with type-II energy band arrangement is an effective way to improve the photodetections. For this purpose, a novel type-II WS₂/Si₂H heterojunction is proposed and investigated for its electronic structures and optoelectronic properties. The WS₂/Si₂H structure is proved to be structurally stable with type-II energy band arrangement for effective carriers separating. The electronic properties and contact type modulated by an external electric field are investigated: A negative electric field leads to an energy band transition from type-II to type-I, while a positive electric field leads to an energy band transition from semiconductor to metal. Rare-earth atoms (RE = Er, Tm, and Lu) and non-metallic atoms X (X = B and P) are used to co-dope the heterojunction. Compared with the non-doping condition, RE and B co-doped heterojunctions WS₂(RE)/Si₂(X)H show type-II and p–p characteristics with 3.1-fold increase in band gap width. The optical absorption peaks locating at about 0.7 eV and 1.4 eV show intensity enhancements of 80 and 15 times, respectively. RE and P co-doped heterojunction shows type-II and p–n characteristics with 1.4 times increase in band gap width. Only one absorption peak is found at 1.4 eV, with the intensity enhancement of 23 times compared with that of the pristine heterojunction. Our work provides useful information for the application of WS₂/Si₂H in photoelectronics.