2D MXenes for Hot‐Carrier Photodetection

Abstract For 2D MXenes (Mo₂C and Ti₃C₂), the fundamental hot‐carrier‐related processes are studied by using the first‐principles calculation, including the material electronic structures, indirect/direct transitions for hot‐carrier generation, electron–electron and electron–phonon scatterings during hot‐carrier transport, and electronic modulation on material to evaluate the potentials of 2D MXenes in hot‐carrier photodetection. It is found that Mo₂C and Ti₃C₂ show higher hot‐carrier generation efficiencies than Au in energy over 1 eV, especially for Mo₂C, which shows better transport performance than Ti₃C₂. Biaxial strain to adjust the electronic structure of Mo₂C is further used to optimize the hot‐carrier transport properties. A Mo₂C/MoGeSiN₄ hot‐electron photodetector is proposed, which shows that the compressive strain (−4%) on Mo₂C material enables a twofold enhancement of the quantum efficiency and responsivity. The Monte Carlo device simulation predicts an extremely high responsivity up ≈176 mA W⁻¹ at the communication wavelength of 1550 nm, which is one order of magnitude over the existing hot‐carrier devices and can be competitive with the existing semiconductor‐based photodetectors.