Propagation Of Terahertz Waves In Rectangular FETs

With the rapid development of semiconductor technology,electromagnetic waves in photonics regions and electronics regions have been extensively studied,and the development prospects of terahertz waves between the photonics regions and electronics regions are very broad.However,the properties of terahertz waves can not be described by both optical theory and microwave theory.Thus,the generation and detection of terahertz waves have not be supported by particularly mature technology nowadays.In 1993 and 1996,Dyakonov and Shur proposed the study of the instability,excitation and oscillation of plasma in a gatecontrolled two-dimensional electron gas channel to explore the radiation,detection and terahertz wave mixing of terahertz waves.This theoretical study laid the theoretical foundation for terahertz generation and detection.At present,solid-state THz devices with semiconductor devices as the core are favored due to their mature and stable manufacturing process and easy integration.Therefore,in this thesis,field effect transistors are selected as solid-state radiation sources and detectors for terahertz signals.The effects of physical effects such as quantum effects on the macroscopic performance of devices are studied and the field effect transistors are analyzed based on the theory of Dyakonov and Shur.Terahertz radiation and response provide theoretical support for experimental research.The specific work is as follows:(1)Based on the basic theory and basic model of hydrodynamic model,more detailed theoretical analysis and numerical simulation of the instability increment and oscillation frequency of plasma waves are carried out.Considering the electron diffusion current density,the effects of quantum effects,external friction of electrons with phonons and impurities,thermal motion of electrons,electron diffusion current density,and electron exchange interaction on current instability in FETs are analyzed under asymmetric boundary conditions.(2)There are two mechanisms that hinder the growth of plasma waves,including external friction caused by electronic collisions with phonons and impurities,and internal friction caused by viscosity.However,the effect of viscosity on plasma waves instability has not been specifically studied,so it is added based on the hydrodynamic model.The effects of electron diffusion current density,quantum effect and electron exchange interaction,external friction of electrons with phonons and impurities on the instability of plasma wave in FET are analyzed.(3)The Dyakonov-Shur model is established by using hydrodynamic mechanics under the condition of channel approximation.The relationship between the response voltage of the terahertz signal in the high mobility field effect transistor and the channel length is described.The behavior of the response voltage is similar to the SDH oscillation.The Dyakonov-Shur model partial differential equation is solved under considering the electron thermal motion and the electron diffusion current density.The first-order solution and the second-order solution response analytical expression are obtained.The numerical simulation image is obtained by Matlab simulation,and its physical meaning is analyzed.