Research on emission of terahertz plasma waves in quantum monolayer black phosphorus field-effect transistors

Monolayer black phosphorus field-effect transistors (MBPFETs) exhibit excellent electrical performance, offering new perspectives for overcoming the physical limitations of traditional silicon-based devices. Using the tight-binding approximation method, a mathematical expression for the pressure term of the two-dimensional electron gas in monolayer black phosphorus was derived and incorporated into the magnetohydrodynamic equations describing the collective behavior of the two-dimensional electron gas in monolayer black phosphorus (MBP). By applying asymmetric boundary conditions, the effects of various physical factors—such as magnetic field, quantum effects, dielectric layer thickness, temperature, electron viscosity, and collision damping—on plasma wave instability gain and terahertz radiation frequency in MBPFETs were systematically investigated. The results indicate that the instability gain decreases with increasing magnetic field, electron viscosity, and collision damping, but increases with enhanced quantum effects. The influence of dielectric layer thickness and temperature on the instability gain depends on the magnitude of the quantum effects. The radiation frequency increases with stronger magnetic fields, quantum effects, dielectric layer thickness, and electron viscosity, but decreases with increasing temperature and collision damping. This study not only explores the characteristics of terahertz electromagnetic radiation in MBPFETs but also compares them with graphene and monolayer molybdenum disulfide (MoS₂) field-effect transistors, analyzing the suitable operational environments for each type of device. The findings provide a solid theoretical foundation for the development of novel field-effect transistors based on two-dimensional channel materials.