Electronic and Optical Properties, and Quantum Capacitance of Twisted III ‐Nitride AlN , BN , and GaN

Twist angle between adjacent two‐dimensional (2D) materials can provide an exotic degree of freedom and lead to superior properties such as fascinating electronic structure, tunable bandgaps, and excellent carrier transport. The electronic and optical properties, and quantum capacitance of AA1 and AA2 stackings of twisted III‐nitride bilayers AlN, BN, and GaN at a 21.79° twist angle are investigated by density functional theory (DFT). Compared with no‐twisted systems, the twisted angle drastically reduces the band gaps of bilayer systems. The stacking mode is sensitive to the electronic structures of twisted bilayer AlN, but insensitive to the electronic structures of twisted bilayers BN and GaN. Flat bands of twisted bilayers AlN and GaN are introduced after atomic reconstruction and mainly originate from N‐p states, especially for AA2 stackings of twisted bilayers AlN and GaN. Twisted bilayer BN has the strongest absorptions of 16.4% for AA1 stacking and 14.8% for AA2 stacking in the ultraviolet region. Electrical conductivity is insensitive to stacking modes, and twisted bilayer GaN possesses the strongest electrical conductivity. Different stacking modes have little impact on the electrode type of twisted bilayer materials. All systems are cathode materials at the whole voltage. Effective mass and work function are further studied.