Control of Conduction Polarity of BiOBr Single Crystal via Chemical Potential Modulation Chemical Vapor Deposition
Two-dimensional (2D) BiOBr has attracted considerable attention for optoelectronic applications, yet reported 2D BiOBr predominantly exhibits n-type conductivity. The absence of high-quality p-type 2D BiOBr impedes the development of complementary metal oxide semiconductor (CMOS) integrated circuits. This study reports the synthesis of large-scale, high-quality p-type 2D BiOBr single crystals via chemical potential modulation chemical vapor deposition (CPMCVD). By precisely modulating the oxygen chemical potential during growth, the conduction polarity of 2D BiOBr is controllably switched between p-type and n-type. Density functional theory calculations reveal that high oxygen chemical potential promotes bismuth vacancy formation, yielding p-type conductivity, whereas low oxygen chemical potential favors oxygen vacancies, resulting in n-type BiOBr. Field-effect transistors (FETs) fabricated from the p-type crystals exhibit a hole mobility of 26.28 cm2 V−1 s−1 and an on/off ratio exceeding 10^4. The n-type FETs demonstrate an electron mobility of 59.59 cm2 V−1 s−1, surpassing most reported n-type 2D FETs. This CPMCVD approach enables precise polarity control without extrinsic doping, offering a scalable route for integrating 2D BiOBr into CMOS technology.