Hot-Carrier Physics of Transition-Metal Carbides and Nitrides: Insight from Electronic Structure

Hot-carrier photodetectors have been extensively studied in recent years, but still exhibit particularly low efficiencies. The physics behind this is closely related to the intrinsic electronic structures of hot-carrier materials. Transition-metal carbides and nitrides (TMCNs) show intriguing potential for high-performance hot-carrier applications; however, a systematic study from the electronic structure perspective remains elusive. Herein, we study the underlying physics, including the electronic structures, hot-carrier energy distribution, electron-electron and electron-phonon scatterings, and hot-carrier injection for TMCNs by first-principles calculation and Monte Carlo simulations. We investigate the complete hot-carrier behavior from the microscopic dynamics (e.g., generation, transport, and injection) of hot carriers to the macroscopic responses (e.g., device responsivity) of the photodetectors. It is found that a well-manipulated electronic structure can greatly improve the performance of hot-carrier photodetectors. Our systematic study shows that hot-carrier systems based on HfC, ZrN, or TaC display significantly higher efficiencies, benefitting from their better electronic structures; in particular, the unbiased responsivity of the ZrN/TiO2 system can be up to 20 mA/W at a wavelength of 1033 nm, which is about 70 times higher than that of the conventional Au system, enabling the realization of high-performance hot-carrier photodetectors by using non-noble metals.